Many road users have crashed at high speed in sharp curves during slippery road conditions. To reduce the skid risk following high lateral forces, outercurves are banked into superelevation. Road designers are guided by design codes into what superelevation values to select among, given a reference speed and curve radius. Curve design codes are based on analysis of cornering forces acting on AASHO’s point-mass model of a vehicle. While the design codes typically yield curves with acceptable safety level, there is a systematic problem with skid accidents on multiple lane curves. This paper discusses a causal factor and recommends changes in curve design codes as well as actions to improve safety in existing unsafe curves. Current road design practise approximates the vehicle travelled path (and thus lateral force) by the road curvature, which is reasonable on small roads. On multiple lane roads however, many drivers are changing lane also in sharp curves since no oncoming traffic is present. When shifting lane quickly, the vehicle experience a transient “curve radius” much sharper than indicated by the road curve radius. This can yield higher lateral force than the road design code have considered. Then the superelevation may be insufficient - when the road is slippery - to outbalance the cornering force. As a rule by thumb, sharp curves on multiple lane roads with high speed traffic should have maximum allowed cross slope in order to increase stability.
Hvtt13 granlund et al lowered crash risk with banked curves designed for heav...Johan Granlund
Outer-curves are banked into superelevation in order to reduce the crash risk due to high demand for side friction between tyres and road. Road design codes use analysis of cornering forces acting on a point-mass model of a vehicle, where the Centre-of-Gravity (CoG) is assumed to be located at the tyre footprint. This may be relevant for low passenger cars. The scope here was to investigate the need for superelevation for heavy goods vehicles (HGV) with high CoG. The study used a vehicle model including both vertical and lateral position of CoG, as well as road split friction under left/right wheels. The results showed that superelevation demand increases with height and lateral displacement of CoG, and peaks when the curve is more slippery under outer wheels than under inner wheels. A conclusion was that the traditional point-mass “car model” can underestimate the superelevation needed for safe HGV operations. The paper recommends some improvements in road design codes for new curves, as well as some actions to improve safety in existing curves.
Vehicle and human vibration due to road condition - ROADEX IVJohan Granlund
This present ROADEX IV follow-up report describes results from demonstration projects in Scotland, Finland, Norway and Sweden over the period 2010 to 2012, where the case study from the Beaver Road 331 in ROADEX III has been reproduced. This document also reports on a study of the influence of road maintenance standard on truck ride vibration and vehicle internal noise, with special focus on winter road condition. Furthermore it reports on a study on vibration isolation from road to truck driver’s seat, by use of a Tyre Pressure Control System (TPCS). All measurements were carried out in the period 2010 - 2012.
A high repeatability between similar truck round trips was confirmed when using the ROADEX method to assess truck drivers’ daily vibration exposure A(8). Results from measurements of truck ride quality during the demonstrations included:
* Unacceptably high levels of driver´s daily vibration dose A(8) were recorded in all of the ROADEX Partner areas (the Norwegian E6-measurements were lower than the others but still at about the EU Action Value).
* Significant compression stress in the truck drivers spine were recorded at severe road damages, such as sharp frost heaves, settlements at bridges and culverts, improper
road/bridge joints and uneven transversal joints at both old and new asphalt repairs.
* In all Partner areas, intense truck roll vibration and lateral buffeting was recorded. This confirmed a special health and safety problem in the EU Northern Periphery (NP) cold
climates.
* The pavement condition parameter RBCSV (a “truck roll vibration indicator”) was further validated in addition to the previous ROADEX III study in Sweden. At sites with very high RBCSV, there is a risk that cargo latches might break due to high lateral acceleration.
* Winter conditions in the NP can result in significant corrugations in thick ice covering nonsalted roads, and extremely uneven frost heaves. The project results show that these conditions can make the ride vibration and noise much worse than during summer conditions.
* The use of a Tyre Pressure Control System (TPCS) has previously been shown to reduce ride vibration. The present study used a more detailed analysis to quantify the TPCS vibration isolating effect. Results from Scotland and Sweden show that TPCS was very efficient in isolating “shake” vibration from short wave road roughness (megatexture < 0.5 m) such as potholes and corrugated ice surfaces.
* Vehicle body “bounce” vibration with lower frequencies (1 – 3 Hz) were not isolated by the TPCS. Such low frequency bounce vibration can only be reduced by pavement maintenance.
* High side friction demand due to improperly banked horizontal curves was found to be a contributing factor behind many loss-of-control crashes, including rollovers.
* Several curves with tragic crash records were found to be improperly banked despite being newly resurfaced.
Health Issues Raised by Poorly Maintained Road Networks - ROADEX IIIJohan Granlund
The EU ROADEX Project 1998 - 2007 is a trans-national roads co-operation aimed at developing
ways for interactive and innovative management of low traffic volume roads throughout the
cold climate regions of the Northern Periphery Area of Europe. Its goals have been to facilitate
co-operation and research into the common problems of the Northern Periphery.
The overall objective for this research task was to increase the understanding for road user’s
health risks when riding on roads in poor condition. Better knowledge will facilitate the reduction
of the risks, by means of improved pavement management, more conscious truck, bus and ambulance
operations, and inspire to vehicle suspension systems improvements.
The report commences with generic descriptions of how safety and health can be affected by
ride vibration, how truck suspension systems isolate and amplify vibration at various frequencies,
and how pavement properties, such as cross slope, control the important forces at work.
A case study is reported from the Beaver Road 331 in northern Sweden. A heavy timber logging
truck was instrumented to measure ride vibration and direction. Measurements were taken at a
range of points (seat, cab, frame and wheels) and the results stored together with data on
speed and interior noise. Ride vibration data from repeated rides over a 280 km long round trip
from forest to coast industries was then compared with reference data on pavement condition,
scanned by a laser/inertial Profilograph. Results obtained included:
• The daily exposure to Whole-Body Vibration, the A(8)-value, for timber truck drivers riding
constantly on roads such as Rd 331 were unacceptably high, when compared to the
health and safety Action Value in Directive 2002/44/EC.
• The truck drivers were exposed to unacceptably health risks in the back when driving at
modest speed over the worst bumps, due to high spinal compression doses, Sed, as per
the ISO 2631-5 standard.
• A derived draft limit of 0.30 % for undesired variance in cross slope. This could be useful
in pavement management to prevent roll-motion and lateral forces in road vehicles.
The case study also produced valuable spin-offs in new methods for analyzing traffic safety
risks arising from incorrectly banked curves and low drainage gradients. Hospital records from
accidents at Rd 331 (mainly skid accidents) were found to match road sections with high cross
slope variance, curves with incorrect superelevation, transition sections with low drainage gradients,
and sections with high skid risk due to low/varying Macro Texture. These serious findings
call for both short and long term actions. Road agencies should use the demonstrated methods
to quickly identify hazardous sites and warn road users of them. Road repair planning and practices
should be improved, and funding for road repair should be increased.
Vibration measurement and spectral analysis of chassis frame mounted structur...Dr.Vikas Deulgaonkar
Chassis mounted structure is a base component for shelters or containers mounted on heavy transport vehicles. When the vehicle is driven in rough terrains or during off-road transportation this structure has a significant role in protecting the sophisticated cargo and intelligent tracking systems placed inside the shelters. During off-road transportation or warhead conditions the vehicle is subjected to large unevenness in load due to road or soil irregularities in rough terrains, which causes vibrations to be induced in the vehicle. As the nature of vibrations induced in vehicle during travel on off-road or cross-country terrains is random and unpredictable, there is a concern to analyse the vibration response of chassis and chassis mounted structures is needed. Present work deals with vibration measurement and spectral analysis of a chassis mounted structure designed for off-road and commercial transport vehicles. The road profile on which the vibration measurement has been carried out includes paved road and cross-country terrain segments. The vibration measurement has been carried at three different vehicle speeds. Signal analysis procedure for the acquired test data is discussed. The chassis mounted structure under concern is intended to hold two shelters or containers. From the vibration measurement at critical locations, g-(RMS) and g-(peak) values for paved and cross-country roads have been found out. Power spectral density values have also been found on chassis and structure for the same transport situations. Major inferences include the evaluation of minimum and maximum g-values (peak & RMS) on chassis and chassis mounted structure. Power spectral density graphs are constructed from which the dominant frequency for both road profiles is found out
Whole-Body Vibrations When Riding on Rough RoadsJohan Granlund
The overall aim of this study was to ascertain the seriousness of the problem of whole-body vibration when driving on roads; ”Is the road roughness such that it entails a health hazard and/or a road safety hazard through its impact on drivers?”. Other objectives were to estimate the scope of the problem during non-frozen ground conditions, to examine the problems and potential related to measurement techniques and to point out the necessity of further research in this field.
The measurement data was collected when driving on 37 kilometres of National Highway No. 90 (Hw 90) and 21 kilometres of County Road 950 (Lv 950) in Västernorrland County. The road condition on the test stretches covered the entire range from very smooth (IRI20 = 0.43 mm/m) to very rough (IRI20 = 22.78 mm/m). Whole-body vibration was measured in compliance with the ISO 2631-1 (1997) standard “Evaluation of human exposure to whole-body vibration”. This was done on stretchers with patients in different types of ambulance and at different speeds, and on the floor and driver and passenger seats for seated occupants in some different truck configurations.
There are three main sources of vibration: road roughness, vehicle properties and driver behaviour (including choice of speed). The interpretation of the results supports the opinion that within reasonable variations in these factors, road roughness plays a considerably greater part than the other two. High-energy, multi-directional vibrations at many natural body part frequencies were found at the seats in trucks. This is serious due to the risk of resonance, meaning a greater reproduction of vibration in the parts of the body afflicted than at the surface from which the vibrations are transferred. Further, the study substantiates findings from earlier studies; i.e., that the high frequency of occupational diseases among commercial drivers, especially in the locomotor systems, is related to rough roads. This relationship is probably strongest in geographic areas where the road roughness level is high on a large percentage of the roads. Where the roughness was greatest, peak values were registered on ambulance stretchers that considerably exceed the level that completely healthy people are assumed to experience as ”extremely uncomfortable” by international standards.
During a 15-minute ride on a stretch of National Highway 90, the vibration level in one type of ambulance was high enough to pose a potential health hazard had a healthy person been exposed to it for as little as 10 minutes a day. It was shown that the vibration on the ambulance stretchers was as great as at the drivers’ seat in wheel loaders loading blasted rock, bulldozers clearing way in forests for new road construction, etc. Vibration problems are even greater in the spring due to seasonal frost damage related additional roughness.
Measuring pavement deflection variance at highway speedsJohan Granlund
A new method for testing pavement condition combines laser/inertial profilometry of unloaded pavement with vibration measurements in a full loaded heavy truck at highway speed. Three types of results are obtained.
1: Truck wheel, frame and cab vibration, as well as driver seat vibration to be compared with exposure guidelines in ISO 2631-1 and limits in directive 2002/44/EC.
2: Three-dimensional road surface geometry data for simulation of ride and calculation of roughness indices.
3: Locations of potential pavement "soft spots". The latter is possible since large pavement deflection variance under the heavy truck cause a quite different vehicle vibration pattern than the pattern excited from the measured unloaded road surface profile.
A tentative accuracy experiment has been done at 4 sites. Recorded seat vibration levels were very high, thus exceeding the EU Action Value in all test runs. The soft spot indications show reasonable repeatability, as well as reproducibility between different driving speeds and between spring time and autumn. Trueness is the most difficult accuracy feature to estimate, since no ideal reference method is at hand neither for variance of local deflection under truck wheel, nor for global deflection under the entire truck. By comparison with FWD, coring and ground penetrating radar results, trueness seems promising. During the tests, a virtual tyre footprint sensor was used for road profiling. Evaluation showed it to bring a large improvement to profiling accuracy. The new high speed measurement method brings excellent opportunities for further research on the entire chain pavement-truck-ride quality interaction.
Paper published at BCRA´05 in Trondheim, Norway.
Hvtt13 granlund et al lowered crash risk with banked curves designed for heav...Johan Granlund
Outer-curves are banked into superelevation in order to reduce the crash risk due to high demand for side friction between tyres and road. Road design codes use analysis of cornering forces acting on a point-mass model of a vehicle, where the Centre-of-Gravity (CoG) is assumed to be located at the tyre footprint. This may be relevant for low passenger cars. The scope here was to investigate the need for superelevation for heavy goods vehicles (HGV) with high CoG. The study used a vehicle model including both vertical and lateral position of CoG, as well as road split friction under left/right wheels. The results showed that superelevation demand increases with height and lateral displacement of CoG, and peaks when the curve is more slippery under outer wheels than under inner wheels. A conclusion was that the traditional point-mass “car model” can underestimate the superelevation needed for safe HGV operations. The paper recommends some improvements in road design codes for new curves, as well as some actions to improve safety in existing curves.
Vehicle and human vibration due to road condition - ROADEX IVJohan Granlund
This present ROADEX IV follow-up report describes results from demonstration projects in Scotland, Finland, Norway and Sweden over the period 2010 to 2012, where the case study from the Beaver Road 331 in ROADEX III has been reproduced. This document also reports on a study of the influence of road maintenance standard on truck ride vibration and vehicle internal noise, with special focus on winter road condition. Furthermore it reports on a study on vibration isolation from road to truck driver’s seat, by use of a Tyre Pressure Control System (TPCS). All measurements were carried out in the period 2010 - 2012.
A high repeatability between similar truck round trips was confirmed when using the ROADEX method to assess truck drivers’ daily vibration exposure A(8). Results from measurements of truck ride quality during the demonstrations included:
* Unacceptably high levels of driver´s daily vibration dose A(8) were recorded in all of the ROADEX Partner areas (the Norwegian E6-measurements were lower than the others but still at about the EU Action Value).
* Significant compression stress in the truck drivers spine were recorded at severe road damages, such as sharp frost heaves, settlements at bridges and culverts, improper
road/bridge joints and uneven transversal joints at both old and new asphalt repairs.
* In all Partner areas, intense truck roll vibration and lateral buffeting was recorded. This confirmed a special health and safety problem in the EU Northern Periphery (NP) cold
climates.
* The pavement condition parameter RBCSV (a “truck roll vibration indicator”) was further validated in addition to the previous ROADEX III study in Sweden. At sites with very high RBCSV, there is a risk that cargo latches might break due to high lateral acceleration.
* Winter conditions in the NP can result in significant corrugations in thick ice covering nonsalted roads, and extremely uneven frost heaves. The project results show that these conditions can make the ride vibration and noise much worse than during summer conditions.
* The use of a Tyre Pressure Control System (TPCS) has previously been shown to reduce ride vibration. The present study used a more detailed analysis to quantify the TPCS vibration isolating effect. Results from Scotland and Sweden show that TPCS was very efficient in isolating “shake” vibration from short wave road roughness (megatexture < 0.5 m) such as potholes and corrugated ice surfaces.
* Vehicle body “bounce” vibration with lower frequencies (1 – 3 Hz) were not isolated by the TPCS. Such low frequency bounce vibration can only be reduced by pavement maintenance.
* High side friction demand due to improperly banked horizontal curves was found to be a contributing factor behind many loss-of-control crashes, including rollovers.
* Several curves with tragic crash records were found to be improperly banked despite being newly resurfaced.
Health Issues Raised by Poorly Maintained Road Networks - ROADEX IIIJohan Granlund
The EU ROADEX Project 1998 - 2007 is a trans-national roads co-operation aimed at developing
ways for interactive and innovative management of low traffic volume roads throughout the
cold climate regions of the Northern Periphery Area of Europe. Its goals have been to facilitate
co-operation and research into the common problems of the Northern Periphery.
The overall objective for this research task was to increase the understanding for road user’s
health risks when riding on roads in poor condition. Better knowledge will facilitate the reduction
of the risks, by means of improved pavement management, more conscious truck, bus and ambulance
operations, and inspire to vehicle suspension systems improvements.
The report commences with generic descriptions of how safety and health can be affected by
ride vibration, how truck suspension systems isolate and amplify vibration at various frequencies,
and how pavement properties, such as cross slope, control the important forces at work.
A case study is reported from the Beaver Road 331 in northern Sweden. A heavy timber logging
truck was instrumented to measure ride vibration and direction. Measurements were taken at a
range of points (seat, cab, frame and wheels) and the results stored together with data on
speed and interior noise. Ride vibration data from repeated rides over a 280 km long round trip
from forest to coast industries was then compared with reference data on pavement condition,
scanned by a laser/inertial Profilograph. Results obtained included:
• The daily exposure to Whole-Body Vibration, the A(8)-value, for timber truck drivers riding
constantly on roads such as Rd 331 were unacceptably high, when compared to the
health and safety Action Value in Directive 2002/44/EC.
• The truck drivers were exposed to unacceptably health risks in the back when driving at
modest speed over the worst bumps, due to high spinal compression doses, Sed, as per
the ISO 2631-5 standard.
• A derived draft limit of 0.30 % for undesired variance in cross slope. This could be useful
in pavement management to prevent roll-motion and lateral forces in road vehicles.
The case study also produced valuable spin-offs in new methods for analyzing traffic safety
risks arising from incorrectly banked curves and low drainage gradients. Hospital records from
accidents at Rd 331 (mainly skid accidents) were found to match road sections with high cross
slope variance, curves with incorrect superelevation, transition sections with low drainage gradients,
and sections with high skid risk due to low/varying Macro Texture. These serious findings
call for both short and long term actions. Road agencies should use the demonstrated methods
to quickly identify hazardous sites and warn road users of them. Road repair planning and practices
should be improved, and funding for road repair should be increased.
Vibration measurement and spectral analysis of chassis frame mounted structur...Dr.Vikas Deulgaonkar
Chassis mounted structure is a base component for shelters or containers mounted on heavy transport vehicles. When the vehicle is driven in rough terrains or during off-road transportation this structure has a significant role in protecting the sophisticated cargo and intelligent tracking systems placed inside the shelters. During off-road transportation or warhead conditions the vehicle is subjected to large unevenness in load due to road or soil irregularities in rough terrains, which causes vibrations to be induced in the vehicle. As the nature of vibrations induced in vehicle during travel on off-road or cross-country terrains is random and unpredictable, there is a concern to analyse the vibration response of chassis and chassis mounted structures is needed. Present work deals with vibration measurement and spectral analysis of a chassis mounted structure designed for off-road and commercial transport vehicles. The road profile on which the vibration measurement has been carried out includes paved road and cross-country terrain segments. The vibration measurement has been carried at three different vehicle speeds. Signal analysis procedure for the acquired test data is discussed. The chassis mounted structure under concern is intended to hold two shelters or containers. From the vibration measurement at critical locations, g-(RMS) and g-(peak) values for paved and cross-country roads have been found out. Power spectral density values have also been found on chassis and structure for the same transport situations. Major inferences include the evaluation of minimum and maximum g-values (peak & RMS) on chassis and chassis mounted structure. Power spectral density graphs are constructed from which the dominant frequency for both road profiles is found out
Whole-Body Vibrations When Riding on Rough RoadsJohan Granlund
The overall aim of this study was to ascertain the seriousness of the problem of whole-body vibration when driving on roads; ”Is the road roughness such that it entails a health hazard and/or a road safety hazard through its impact on drivers?”. Other objectives were to estimate the scope of the problem during non-frozen ground conditions, to examine the problems and potential related to measurement techniques and to point out the necessity of further research in this field.
The measurement data was collected when driving on 37 kilometres of National Highway No. 90 (Hw 90) and 21 kilometres of County Road 950 (Lv 950) in Västernorrland County. The road condition on the test stretches covered the entire range from very smooth (IRI20 = 0.43 mm/m) to very rough (IRI20 = 22.78 mm/m). Whole-body vibration was measured in compliance with the ISO 2631-1 (1997) standard “Evaluation of human exposure to whole-body vibration”. This was done on stretchers with patients in different types of ambulance and at different speeds, and on the floor and driver and passenger seats for seated occupants in some different truck configurations.
There are three main sources of vibration: road roughness, vehicle properties and driver behaviour (including choice of speed). The interpretation of the results supports the opinion that within reasonable variations in these factors, road roughness plays a considerably greater part than the other two. High-energy, multi-directional vibrations at many natural body part frequencies were found at the seats in trucks. This is serious due to the risk of resonance, meaning a greater reproduction of vibration in the parts of the body afflicted than at the surface from which the vibrations are transferred. Further, the study substantiates findings from earlier studies; i.e., that the high frequency of occupational diseases among commercial drivers, especially in the locomotor systems, is related to rough roads. This relationship is probably strongest in geographic areas where the road roughness level is high on a large percentage of the roads. Where the roughness was greatest, peak values were registered on ambulance stretchers that considerably exceed the level that completely healthy people are assumed to experience as ”extremely uncomfortable” by international standards.
During a 15-minute ride on a stretch of National Highway 90, the vibration level in one type of ambulance was high enough to pose a potential health hazard had a healthy person been exposed to it for as little as 10 minutes a day. It was shown that the vibration on the ambulance stretchers was as great as at the drivers’ seat in wheel loaders loading blasted rock, bulldozers clearing way in forests for new road construction, etc. Vibration problems are even greater in the spring due to seasonal frost damage related additional roughness.
Measuring pavement deflection variance at highway speedsJohan Granlund
A new method for testing pavement condition combines laser/inertial profilometry of unloaded pavement with vibration measurements in a full loaded heavy truck at highway speed. Three types of results are obtained.
1: Truck wheel, frame and cab vibration, as well as driver seat vibration to be compared with exposure guidelines in ISO 2631-1 and limits in directive 2002/44/EC.
2: Three-dimensional road surface geometry data for simulation of ride and calculation of roughness indices.
3: Locations of potential pavement "soft spots". The latter is possible since large pavement deflection variance under the heavy truck cause a quite different vehicle vibration pattern than the pattern excited from the measured unloaded road surface profile.
A tentative accuracy experiment has been done at 4 sites. Recorded seat vibration levels were very high, thus exceeding the EU Action Value in all test runs. The soft spot indications show reasonable repeatability, as well as reproducibility between different driving speeds and between spring time and autumn. Trueness is the most difficult accuracy feature to estimate, since no ideal reference method is at hand neither for variance of local deflection under truck wheel, nor for global deflection under the entire truck. By comparison with FWD, coring and ground penetrating radar results, trueness seems promising. During the tests, a virtual tyre footprint sensor was used for road profiling. Evaluation showed it to bring a large improvement to profiling accuracy. The new high speed measurement method brings excellent opportunities for further research on the entire chain pavement-truck-ride quality interaction.
Paper published at BCRA´05 in Trondheim, Norway.
Need ornamentation.This was a crude copy.Special Thanks to AUST'ian.BUET ian should make a new way of reporting.Dont mind to found enomous mistake in mine..It was prepared in a very short time
International Roughness Index, IRI, and ISO 2631 Vibration EvaluationJohan Granlund
Every road authority targets good ride quality in their pavement management. Ride quality depends strongly on the experienced vibrations, induced by road roughness. International Roughness Index, IRI, is the most common way to describe road roughness, while ISO 2631 defines how to measure human whole body vibration (WBV) experienced by the driver and the passengers during the ride. IRI is defined by means of a quarter car model, and the same model is here used to get a relation between IRI-values and vertical human vibrations as defined in ISO 2631. Criterions for discomfort, activities/safety and (occupational) health are the reasons for vibration limits in the ISO 2631 standard. The relation between IRI and human WBV helps us therefore to create management policies for road roughness limits, to be used in our pavement management systems.
Road bumps reduce vehicle speeds on residential streets and other densely populated areas, thus improving safety and comfort for pedestrians and bicyclists. Unfortunately, the effects on health and safety for drivers and passengers passing these obstacles are rarely considered by road agencies, consultants and contractors. Many current bumps induces harmful whole-body vibration and shock when passing, even at legal speeds. Injuries can be immediate, e.g. fracture of vertebrae, or long term, e.g. low back pain. Bus drivers in many cities pass up to 40.000 bumps per year. The bumps will also cause additional longitudinal and vertical stress to the vehicle. A literature review shows that previous research on the subject of road bumps has been severely misinterpreted. As a result, bumps are in many countries today designed to cause a high maximum vertical acceleration (shock) level. To cause shocks on purpose, is in obvious conflict with ergonomic knowledge such as in directive 2002/44/EC. In a project described in this paper, a “shock-free” speed hump has been designed using vibration engineering. The new hump cause uncomfortable vibration at high driving speeds, but only a minimum of shock occur when passing. In 2003 the first hump ramps of this design were casted in Portland Cement Concrete, available from www.gunnarprefab.se
Investigating Heavy Vehicle Rollover Crashes and the Influence of Road DesignJohan Granlund
Paper presented at the International Heavy Vehicle Transport Technology HVTT14 Symposia in Rotorua, New Zealand, in Nov 2016.
The HVTT conferences are organized by the International Forum for Road Transport Technology, IFRTT.
Need ornamentation.This was a crude copy.Special Thanks to AUST'ian.BUET ian should make a new way of reporting.Dont mind to found enomous mistake in mine..It was prepared in a very short time
International Roughness Index, IRI, and ISO 2631 Vibration EvaluationJohan Granlund
Every road authority targets good ride quality in their pavement management. Ride quality depends strongly on the experienced vibrations, induced by road roughness. International Roughness Index, IRI, is the most common way to describe road roughness, while ISO 2631 defines how to measure human whole body vibration (WBV) experienced by the driver and the passengers during the ride. IRI is defined by means of a quarter car model, and the same model is here used to get a relation between IRI-values and vertical human vibrations as defined in ISO 2631. Criterions for discomfort, activities/safety and (occupational) health are the reasons for vibration limits in the ISO 2631 standard. The relation between IRI and human WBV helps us therefore to create management policies for road roughness limits, to be used in our pavement management systems.
Road bumps reduce vehicle speeds on residential streets and other densely populated areas, thus improving safety and comfort for pedestrians and bicyclists. Unfortunately, the effects on health and safety for drivers and passengers passing these obstacles are rarely considered by road agencies, consultants and contractors. Many current bumps induces harmful whole-body vibration and shock when passing, even at legal speeds. Injuries can be immediate, e.g. fracture of vertebrae, or long term, e.g. low back pain. Bus drivers in many cities pass up to 40.000 bumps per year. The bumps will also cause additional longitudinal and vertical stress to the vehicle. A literature review shows that previous research on the subject of road bumps has been severely misinterpreted. As a result, bumps are in many countries today designed to cause a high maximum vertical acceleration (shock) level. To cause shocks on purpose, is in obvious conflict with ergonomic knowledge such as in directive 2002/44/EC. In a project described in this paper, a “shock-free” speed hump has been designed using vibration engineering. The new hump cause uncomfortable vibration at high driving speeds, but only a minimum of shock occur when passing. In 2003 the first hump ramps of this design were casted in Portland Cement Concrete, available from www.gunnarprefab.se
Investigating Heavy Vehicle Rollover Crashes and the Influence of Road DesignJohan Granlund
Paper presented at the International Heavy Vehicle Transport Technology HVTT14 Symposia in Rotorua, New Zealand, in Nov 2016.
The HVTT conferences are organized by the International Forum for Road Transport Technology, IFRTT.
Reducing health and safety risks on poorly maintained rural roads, granlundJohan Granlund
This paper presents a handful of methods to measure road alignment properties and pavement damages that bring health and safety risks. These methods can be used in new approaches to reduce disproportionally high risks in hot spots on the low-volume road network. Suitable actions include road curve reconstruction, reinforcement of road edge or entire pavement, resurfacing or retexturing the wearing course, as well as mounting intelligent warning signs using radar for detection of excessive vehicle speed. The potential for crash reduction is high at hot spot road sections, especially where friction is low. This paper ends with a consensus statement on the urgent need to implement such approaches in road management. The statement is given by the Nordic Road Associations (NVF) working group “Vehicles and Transportation”, consisting of about 50 recognized experts in the fields of heavy vehicles, transportation and of vehicle-road interaction
Notes on the formula for minimum horizontal radius. Rev. 05 (January 2016) - Added notes on different measures of speed and different speeds for horizontal and vertical
design. Added row h to values table. Modified layout. Added extra note and reference on 3D road design.
Traffic safety risks with EU-semitrailers on slippery roads.
Safety gains for heavy trailers from increased crossfall in road curves.
C/B-analysis: Increasing crossfall is profitable.
Wide shoulder: Effective “barrier” to crashes.
Sweden implementing new pavement condition parameter "Rut Bottom Cross Slope Variance" (tvärfallsvariation) in 2016.
Improved heavy vehicle safety by increased lane widening in curves.
Cutting fuel consumption tenfold per cents, by repair of road damages
In this paper, I argue that modern roundabouts are a highly favorable solution for roadway intersections because of their benefits with regards to safety, environmental factors, and traffic flow efficiency. I begin by addressing public opinion of roundabouts and then explaining their safety benefits. Next, I demonstrate how roundabouts can overcome commonly perceived drawbacks related to usage by pedestrians, cyclists, oversize vehicles, and emergency vehicles. The penultimate sections are devoted to the cost and land considerations and the environmental benefits associated with roundabouts. Lastly, I show how roundabouts improve traffic flow efficiency and conclude that, all factors considered, roundabouts are a highly favorable design solution.
The Impact of the Combination of Circular Curve and Transition Curve on Highw...IJERA Editor
By investigating the accident in 2009 and 2011 of Taijiu Expressway, the study analyzed the relationship
between the horizontal curve radiuses, the length of horizontal curve, the length of transition curve and the
number of accidents, established the corresponding regression model. The trend of accidents was determined
with different length of transition curve and different combination of circular curve according to this model. The
results show that the circular curve radius and length of transition curve increase with the decreases of accidents
number, the number of accidents decreases with the increase of the ratio of the length of the transition curve and
the length of the round curve. When the ratio of the parameters of the transition curve and the radius of the circle
is between 0.3-0.6, the accidents are more focused. The bigger change rate of curves is, there are more accidents
of flat curve. To evaluate road traffic safety from the perspective of horizontal curve alignment design, these
regularities have very important reference.
Lowered crash risk with banked curves designed for heavy trucks, granlund et ...Johan Granlund
Slides from the presentation at HVTT13 in San Luis (Argentina) of our paper with the same title. Note that the full paper is available here at Slideshare.
CAD CAM pavement maintenance actions -An efficient method to reduce human who...Johan Granlund
The main source to ride vibration in vehicles is road roughness. Many professional drivers are exposed to human whole-body vibration (WBV) exceeding the limit for acceptable occupational exposure. Much vibration is at low frequencies, coinciding with resonance frequencies in road vehicle chassis, cab and seat suspension systems. Such vibration is at highway speed caused by very long wave road unevenness; from 5 m up to more than 40 m. Efficient repair of such road damages is not achieved by traditional resurfacing, but is possible with modern CAD/CAM mill and fill actions before paving the new wearing course.
International Journal of Computational Engineering Research(IJCER)ijceronline
International Journal of Computational Engineering Research(IJCER) is an intentional online Journal in English monthly publishing journal. This Journal publish original research work that contributes significantly to further the scientific knowledge in engineering and Technology.
Dynamic analyses of ship impact to the new bridge over storstrømmenJacob Egede Andersen
Ship impacts to bridges are relatively rare and therefore treated as accidental loads. Due to the
low probability of occurrence, it is logical to allow some degree of plastic behaviour of the
impinged structure, since the alternative, a completely elastic response, may lead to
disproportionally large material usage.
This paper presents the principle of, and results from, numerical analyses conducted for the
illustrative design of the new bridge over Storstrømmen in Denmark. This is an approximately 4km
long bridge consisting of 80m viaduct spans and two navigations spans of 160m in a single-pylon
cable-stayed configuration. The girder is a continuous, post-tensioned concrete box girder carrying
two railway tracks, two road lanes and a combined pedestrian/bicycle path.
Since ship impact is a transient event, the numerical analyses conducted consist of dynamic
analyses in the form of time-series that include relevant non-linearities of the ship, soil and bridge
bearings. Hereby a realistic picture of the bridge response during, and after, impact is obtained
allowing the comparison between pre-defined failure modes and the bridge response.
In addition, the time-series produced are used to calibrate a linear model for train
safety/runability calculations in conjunction with ship impact to define design criteria's for
maximum bridge accelerations levels at ship impact, in order to prevent trains from overturning.
The runability model itself have be tested against the Danish Great Belt West Bridge, a comparable
railway concrete girder bridge, in order to justify that the model gives correct acceleration levels
for the train/structure interaction and subsequently acceleration levels at ship impact.
Based upon the investigations made also risk analysis have been carried out, in order to show the
overall risk complies with railway authorities and Eurocode requirements.
Modeling of driver lane choice behavior with artificial neural networks (ann)...cseij
In parallel to the economic developments, the importance of road transportation was significantly
increased in Turkey. As a result of this, long-distance freight transportation gains more importance and
hence numbers of the heavy vehicles were significantly increased. Consequently, road surface deformations
are observed on the roads as the increasing freight transportation and climatic conditions influence the
road surface. Therefore, loss of functionality of the road surface is observed and drivers are much prone to
accident due to their driving characteristics as they can have more tendencies to change their lanes not to
pass through the deformation area. In this study, the lane changing behaviors of the drivers were
investigated and both Artificial Neural Network (ANN) and Linear Regression (LR) models were proposed
to simulate the driver behavior of lane changing who approach to a specific road deformation area. The
potential of ANN model for simulating the driver behavior was evaluated with successive comparison of the
model performances with LR model. While there was a slight performance increase for the ANN model with
respect to LR model, it is quite evident that, ANN models can play an important role for predicting the
driver behavior approaching a road surface deformation. It can be said that, approaching speed plays an
important factor on the lane changing behavior of a driver. This can be criticized by the fact that, drivers
with high approaching speeds more likely pass through the deformation to avoid the accidents while
changing their lanes with a high speed.
A new method for testing pavement condition combines laser/inertial profilometry of unloaded pavement with vibration measurements in a full loaded heavy truck at highway speed. Three types of results are obtained.
1: Truck wheel, frame and cab vibration, as well as driver seat vibration to be compared with exposure guidelines in ISO 2631-1 and limits in directive 2002/44/EC.
2: Three-dimensional road surface geometry data for simulation of ride and calculation of roughness indices.
3: Locations of potential pavement "soft spots". The latter is possible since large pavement deflection variance under the heavy truck cause a quite different vehicle vibration pattern than the pattern excited from the measured unloaded road surface profile.
A tentative accuracy experiment has been done. Recorded seat vibration levels were very high, thus exceeding the EU Action Value in all test runs. The soft spot indications show reasonable repeatability, as well as reproducibility between different driving speeds and between spring time and autumn. Trueness is the most difficult accuracy feature to estimate, since no ideal reference method is at hand neither for variance of local deflection under truck wheel, nor for global deflection under the entire truck. By comparison with FWD, coring and ground penetrating radar results, trueness seems promising. During the tests, a virtual tyre footprint sensor was used for road profiling. Evaluation showed it to bring a large improvement to profiling accuracy. The new high speed measurement method brings excellent opportunities for further research on the entire chain pavement-truck-ride quality interaction.
Accurate Measurement of Runway Pavement GeometriesJohan Granlund
Paper presented at the Airfield Ad-hoc Working Group Meeting, arranged as a satellite conference during the 23rd PIARC World Road Congress held in Paris, France, 2007.
Bildspel från föredrag inom Vecturas ledarutveckling.
Målet var att föra fram organisationen mot ännu bättre resultat.
Innehåll:
• Ledarskapsteorin ”Utvecklande Ledarskap”.
• Att leda i framtidens samhälle.
• Tre ledarstilar i korthet.
• Att skapa positiva känslor.
• Utvecklande beteenden.
Geometrisk vägbeläggningsprojektering inför mötesfri landsvägJohan Granlund
Geometrisk projektering och datorstödd maskinstyrning vid underhåll eller ombyggnad av vägbanans beläggning skapar en rad nyttor:
* Förbättrad färdkvalitet för trafikanterna.
* Minskad risk för trafikolyckor.
* Minskad risk under ambulanstransporter (ca 1500 avlidna/år).
* Minskad förbrukning av vägsalt.
* Bättre produktionsplanering och ekonomistyrning för vägprojekt.
* Minskade kostnader för framtida underhåll av vägbana och vägräcken.
Uppsats från Vägverkets konferens om mötesfria vägar med växelvis omkörningsfält och mittbarriär, så kallade 2+1 vägar.
Vägnära häckar, buskar, träd och annan växtlighet i BäsnaJohan Granlund
Information om vägföreningens respektive fastighetsägares ansvar:
Säker och framkomlig trafik på bostadsgator kräver fri sikt. Varje år skadas människor i onödan för att sikten skyms. Du som har en häck, träd, mur eller staket mot en gata måste se till att sikten är fri. Några enkla åtgärder före och under sommaren kan rädda liv.
Kan jämnhetsstandarden hos det svenska vägnätet förorsaka fordonsskador och o...Johan Granlund
Johans kommentarer till rubricerat VTI Notat 21-1998:
I VTI notat 21-1998 dras slutsatsen att ”det svenska vägnätet är av så god jämnhetsstandard att av bristande jämnhet förorsakat fordonsslitage och / eller skador bör vara av tämligen marginell betydelse, sett i relation till de totala fordonskostnaderna”. Slutsatsen baseras på studier utförda utan hänsyn till andra brottmekanismer än utmattning, utan inverkan av kallt klimat, utifrån påkänningsmätningar i fordon som avviker stort från vanliga svenska lastbilsekipage (totalviktsskillnader på ca 2200 % mellan mätningens sportbil och en vanlig, lagligt lastad, svensk 4-axlad tung släpvagn), samt utan hänsyn till att Vägverkets rutinmässiga vägytemätningar, vilka avser mindre än en femtedel av det svenska vägnätet, har bruksvillkoret ”otjälad vägbana”. Nämnda bruksvillkor medför en snedvriden bild av ens det statliga belagda vägnätets tillstånd sett över hela året. Enligt här redovisad översiktlig verksamhetsuppföljning hos svenska aktörer inom transportnäringen, medför vägojämnheter på svenska vägar sannolikt mycket stora merkostnader för slitage och skador. I vissa fall medför vägojämnheterna att speditörer vägrar utföra transporter, vilket utgör ett hot mot näringsliv i glesbygd och ytterst mot landets tillväxt. Merkostnaderna för skador och slitage kan sannolikt motsvara en betydande andel av annuiteten av kostnaderna för ett vanligt underhållsprojekt. Transportörernas merkostnader härrör från skador som fjäderstocksbrott, axelbrott, rambrott (!) och liknande, samt från slitage av däck, bromsbelägg, draganordningar mm, samt indirekta kostnader. Fortsatt forskning förefaller ha hög nyttopotential och bör inriktas på monetär kvantifiering av merkostnader för tung trafik pga tjälrelaterade ojämnheter, trumslag och kanthäng. Refererad slutsats i VTI notat 21-1998 framstår som felaktigt underbyggd, och notatet i helhet som starkt vilseledande.
Bildspel från redovisning av hastighetsmätning med radar på länsvägen förbi skolan i Bäsna by (Gagnefs kommun, Dalarnas län), med dess dagis, förskoleklass samt lågstadium klass 1 - 3.
Hastighetsmätning utförd år 2006.
Bildspel från mitt föredrag vid Load Up North i Umeå, 2019.
Exempel på allvarliga fel och brister i Trafikverkets däckrapport:
• Ingen hänsyn till risk för livsfarliga vältolyckor.
• Vägslitage beräknat för irrelevanta lastfall 50 á 60 kN på standard 385 mm breddäck, dvs olaglig överlast.
• Ingen hänsyn till minskad dynamisk vägbelastning.
• Missat att högkapacitetsfordon ger sänkt axellast på alla vägar, inkl. BK4, och radikalt minskat vägslitage i synnerhet på de 4300 km svagaste vägarna (BK2 & BK3).
• Däckrapporten saknar uppdelning av hur kostnad för vägunderhåll påverkas av trafiklast respektive klimat, byggfel mm. Enligt Vägverket (2000) vållas inte mer än 1/4
av kostnaden av trafiklast.
• Helt orealistiskt överdriven uppskattning av vägunderhållskostnad från trafik.
Ansvarsfull hänsyn inkluderar att se möjligheter, snarare än överdriva problem.
Samhället vinner på att låta åkaren välja däckkonfiguration.
Polisen saknar lagrum att bötfälla åkare som kör med enkelmontage på väg där TRV kräver dubbelmontage.
Minska vältrisken vid körning med hög tyngdpunkt, VETA GranlundJohan Granlund
Bildspel från föredrag vid Mittia Skogstransportmässa 2019.
Innehåll:
Fokus på de livsfarliga vältolyckorna.
Video om förebyggande av vältolyckor.
TYA handbok om körning med hög tyngdpunkt.
Haveriutredning av svenskt timmerekipage vid E6 Svinesundparken.
Vägens utformning; i flera fall farliga brister t o m i vägreglerna!
Vägens bärighet; ofta svag vägkant vid vältolyckor med lastbil.
Vägens säkerhetszon.
Bristande vägkvalitet är miljöboven - inte dubbdäckenJohan Granlund
Artikel i Nordsverige om trafikant- och miljönyttor med stålhård porfyr i asfaltslitlager och till dammfri halkstopp. Vid tillverkning av asfalt blandas grus och sand i olika fraktioner med bindemedlet bitumen. Till slitlager på högtrafikerade vägar används sedan länge hård specialsten i asfaltgrusets grövsta fraktion, medan en utbredd praxis är att fingruset och sanden är av ortens svaga bergmaterial. De mindre kornen tål därmed inte slitage från dubbade vinterdäck, medan de grövre kornen tål dubbslitage. Detta gör att redan efter kort tids trafikering så får asfaltens yta i hjulspåren mycket 'rå' textur, medan spårslitaget hålls i schack av det hårda grova grusets stentoppar. Dubbarnas slitage av fingruset ger luftburna partiklar som kan påverka hälsan. Den råa vägytan ger ohälsosamt trafikbuller både i fordon och till vägnära miljöer, samt ökat rullmotstånd och därmed ökad förbrukning av drivmedel (energi) och mer avgasutsläpp så som av växthusgasen koldioxid samt toxiska kväveoxider. Genom att istället i ALLA ballastfraktioner ersätta ortens svaga berg med stålhård porfyr så minskas slitaget av vägytans textur, så att luftkvaliteten hålls uppe.
Tätortsluftens kvalitet hålls också bättre genom att halkbekämpa med halkstopp av stålhård porfyr istället för med vintersand av ortens mjuka gråberg.
Optimalt däckval; dubbel- eller enkelmontage?Johan Granlund
Bildspel från föredrag vid Sveriges Åkeriföretags konferens 'Effektivare transporter' 2019.
Sammanfattning av åkerinäringens granskning av Trafikverkets däckrapport 'Konsekvenser av olika däckskonfigurationer för tunga fordons inverkan på vägnätet'.
Bildspel från föredrag vid Sveriges Åkeriföretags konferens 'Effektivare Transporter' 2019.
Sammanfattning av uppdragsrapport 'Förkortad väglivslängd; orsaker och kostnader', framtagen för den svenska åkerinäringen.
Bildspel från föredrag vid PRO Dalarnas trafiksäkerhetsdag 2019. Den mest typiska dödsolyckan sker i farligt tvär eller nypande, feldoserad kurva på lågtrafikerad länsväg med 50 - 80 km/tim hastighetsgräns och med smala körfält, smal vägren samt brant vägslänt. För att effektivt minska antalet svåra trafikolyckor behövs ökning av drift och underhåll på länsvägarna.
Fallstudie av beläggningsunderhåll på enskilt vägnät, Strategi och taktiskt g...Johan Granlund
Bildspel från föredrag vid förbundsstämma 2019 i Riksförbundet Enskilda Vägar. Bäsna Vägars Samfällighet har beslutat om vision och strategi för beläggningsunderhållet. Föredraget visar hur vägåtgärderna har taktiskt genomförts under sex år; dåliga och goda erfarenheter, samt visar framtiden för vägunderhållet på byns enskilda vägnät.
Reduced Pavement Service Life - Causes and Costs, HVTT15 paperJohan Granlund
Pavement loads and road wear have become hot topics in Sweden, due to both an increase of gross combination weight to 74 tonnes and a governmental investigation on a new road wear fee for heavy vehicles. To balance the governmental investigation, the road haulage industry made an independent expert investigation on causes and costs of reduced pavement service life. This paper summarizes the expert report into English. A literature study on factors that cause shortened pavement life cycle explain causes of non-traffic related damages. The annual total cost for maintenance of paved state roads in Sweden was in this investigation split into repair of traffic load related damages and of non-traffic related damages. A reference cost for road damage from heavy vehicles was estimated, by dividing costs for traffic load related damages with heavy vehicle traffic work. Using the Fourth Power Law, the road damaging effect of eleven heavy vehicle combinations were calculated while considering also axle and tyre configurations. Finally, the reference cost for repair of traffic load related damages was distributed to each vehicle combination. Hereby it became possible to compare the estimated vehicle specific cost for road damage versus the fee proposed by the governmental investigation. The ratio between state accounted cost for road damage from heavy vehicles and state proposed fee for road wear is about 1:8. This showed that the proposed fee is very high, being a tax rather than representing true cost coverage. After the industry reported this finding, the government withdrew their investigation on a fee.
Lysbilde fra mitt inlegg 'Trafikksikker fremkommelighet' ved Vegsikringskonferansen 2018 i Lillehammer, arransjert av Trafikksikkerhetsforeningen:
* Antall drepte i vegtrafikk øker nå i Sverige; mine teorier om hvorfor.
* Typiske kjennetegn av ulykkessted.
* Sverige vil stoppe vinterfarlige EU-semitrailers med kort trekkvogn.
* «Vinterdekk» på tungbil: Bedre krav enn M+S må innføres.
* Skråkant på veidekke og oppgrusing av skulder sparer liv. Nå införer Sverige skråkant, mens Norge tappet kravet sitt.
* Erfaringer fra trafikkulykker => Bedre normaler & veiadministrasjon.
1. Transport Research Arena Europe 2010, Brussels
Safer Curves on Multiple Lane Roads
Johan Granlund
IPMA certified Senior Project Manager
Vectura Consulting AB
Röda vägen 1, Box 874, SE-781 28 BORLÄNGE, SWEDEN
johan.granlund@vectura.se
Abstract
Many road users have crashed at high speed in sharp curves during slippery road conditions. To
reduce the skid risk following high lateral forces, outercurves are banked into superelevation.
Road designers are guided by design codes into what superelevation values to select among,
given a reference speed and curve radius. Curve design codes are based on analysis of cornering
forces acting on AASHO’s point-mass model of a vehicle. While the design codes typically yield
curves with acceptable safety level, there is a systematic problem with skid accidents on multiple
lane curves. This paper discusses a causal factor and recommends changes in curve design codes
as well as actions to improve safety in existing unsafe curves. Current road design practise
approximates the vehicle travelled path (and thus lateral force) by the road curvature, which is
reasonable on small roads. On multiple lane roads however, many drivers are changing lane also
in sharp curves since no oncoming traffic is present. When shifting lane quickly, the vehicle
experience a transient “curve radius” much sharper than indicated by the road curve radius. This
can yield higher lateral force than the road design code have considered. Then the superelevation
may be insufficient - when the road is slippery - to outbalance the cornering force. As a rule by
thumb, sharp curves on multiple lane roads with high speed traffic should have maximum
allowed cross slope in order to increase stability.
2. Transport Research Arena Europe 2010, Brussels
1. Introduction
Horizontal road curves were recognised as a problem thousands of years ago. Evidence is present
in the book of the prophet Isaiah: “A voice of one calling in the desert; -Prepare the way for the
Lord, make straight paths for him. Every valley shall be filled in, every mountain and hill made
low. The crooked roads shall become straight, the rough ways smooth”.
Since the introduction of the automobile, cornering is made at highway speeds and is associated
with lateral forces that may bring instability and thus crash risk. Therefore it is not surprising that
horizontal curvature correlates strongly with crash rates on rural highways. After analysing 34
000 road crashes in the United States, Gupta & Jain (1975) found that curvature actually is a
more important factor than road width, vertical clearance as well as sight distance. They also
noted that especially head-on collisions, collisions with fixed objects and rollover crashes occur
disproportionately on curved road sections.
There is good agreement in the road safety research community that sharper curves cause more
accidents (Charlton & de Pont 2007). Crash rates in curves have been found to be typically 2 to
4.5 times higher than on straight road sections (Johnston 1982; Leonard et al. 1994). Trucks
show the highest raise in crash rates between straight and curved road sections. Single sharp
curves in highways with long straight sections as well as improperly banked curves (especially
“flat curves”) create some of the most hazardous situations (Haywood 1980). A study of all fatal
single crashes during four years in Sweden showed that outercurves count for five times more
crashes than innercurves (Lindholm 2002). The EU project Roadex found that hazardous
improper cross slope is several times more frequent in outercurves than in innercurves (Granlund
2008). This finding is to be explained by road history. Ancient dirt roads were built with a
crown, with cross slopes to the nearest roadside to maximize rain water drainage. The road
section was the same in both straight sections and curves. There was simply no need for banking
up superelevation in outercurves, since the non-motorized carriages didn’t reach speed levels
where side forces become high. As dirt roads have been upgraded to tarmac roads, many ancient
outercurves have not yet been updated with enough superelevation to meet the needs of the
motorized road users.
Also on modern highway curves, systematic problem with instability-accidents can be found.
One case is sharp high speed multiple lane curves. This is exemplified by the 90 km/h curve on
European Highway Nr 4 in Skönsberg, see Figure 1. Every third car crash in Sundsvall occurs in
the Skönsberg area; see the crash map in Figure 2 and note that crash dots are piled in the curve.
Figure 1 The Skönsberg Curve on E4 Highway North of Sundsvall City, Sweden
3. Transport Research Arena Europe 2010, Brussels
Figure 2 Crashes Reported by the Rescue Department of Sundsvall During 10 Years
According to the Swedish Traffic Accident Data Acquisition (STRADA) database, at least 82 %
of the reported crashes in Skönsberg have involved skidding. 65 % have taken place with the
road being reported as slippery due to rain, snow or ice. 29 % of all crashed vehicles were
actively reported as making a lane-change. These figures are extremely disproportionate, since
the E4 highway is dry most of the time and only a small fraction of our driving time is spent on
changing lane on the highway.
What is the reason for the disproportionate crash rate in multiple lane curves such as in
Skönsberg, and how can the crash risk be reduced?
2. Reducing the Crash Risk in Multiple Lane Curves
The objective of this paper is to discuss a cause to the excessive crash rates observed in sharp
multiple lane curves. The paper will also recommend changes in curve design codes as well as
actions to improve safety in existing unsafe curves on multiple lane roads. In addition the paper
will also pinpoint the need for improved education of motor vehicle drivers.
3. Design of Cross Slope in Horizontal Curves
Modern design of cross slope (a k a cross fall) in curves is based on the principle that it shall join
force with the side friction between tyre and road, so they together outbalance the lateral force
caused by driving through a curve at highway speed. In outercurves this is achieved by banking
the cross slope into sufficient superelevation.
3.1 The Exciting Lateral Force
As described by Newton’s second law of mechanics, cornering vehicles undergo centripetal
acceleration acting toward the centre of the curvature. As seen in Formula 1, the associated
lateral1 force F is a product of vehicle mass m [kg] and squared vehicle speed v [m/s], divided
by the curve radius R [m]. For a vehicle with given reference speed, the lateral force depends
1 In Figure 3 the centripetal acceleration is substituted by a corresponding centrifugal force in the opposite direction. Even though people
in a cornering vehicle perceive a “centrifugal force”, it is fictive (not real) on the vehicle. This paper follows the practice set used
in many road design manuals, by referring to the (fictive) centrifugal force, rather than to the fundamentally correct centripetal
acceleration with opposite direction.
4. Transport Research Arena Europe 2010, Brussels
only on the curve radius. Smaller radii (tighter curves) yield higher lateral forces. For tight
curves, even a minor increase in radius results in a large decrease of the lateral force.
m * 2
F
R
Formula 1, Lateral Acceleration Force Acting on a Cornering Vehicle
Figure 3 shows the factors influencing the cornering forces acting on a vehicle as described by
the AASHO point mass model used in road design manuals worldwide (Psarianos et al, 1995).
These are the gravitational force G [N], the normal force N [N], the lateral force F [N], the side
friction demand factor fs [-], and the tangent of the angle corresponding to pavement
superelevation/banking/cross slope [%].
Figure 3 Vehicle Cornering Forces
Note that the total road grip between tyre and pavement can be divided into a tangential part
(braking friction, longitudinal direction) and a radial part (side friction, lateral direction). The
side friction is the part of the total road grip normally utilized when cornering.
3.2 The Reaction Forces Needed to Balance the Ride
If the lateral force F is not balanced by reaction forces, the vehicle ride will become unstable and
the risk of a traffic accident (run-off, skidding and rollover modes) will increase. There are two
reaction forces that may balance the lateral force F. One is the horizontal component of the
normal force; N * sin(). The other is the horizontal component of the side friction developed
between the vehicle's tyres and the pavement surface friction force, N * fs * cos(). This can be
expressed by the equation in Formula 2.
F N * sin( ) N * f s * cos( )
Formula 2, Lateral Equilibrium; Initial Setup
5. Transport Research Arena Europe 2010, Brussels
After division by cos (), substitution with N = m * g (g being the gravitation constant) and with
F as per Formula 1, elimination of m and recalling that cos() is close to 1 for small angles
(from a mathematical point of view, pavement cross slopes are small angles), the equation is,
with good approximation, expressed as Formula 3.
2
tan( ) f s
R* g
Formula 3, Lateral Equilibrium; Final Expression
Now recall that tan(α) represents the cross slope. Clearly, Formula 3 shows that a prerequisite
for steady cornering is that the sum of the cross slope and the side friction demand factor is high
enough to outbalance the effect of vehicle speed, of the vehicle’s curved path and of gravity.
Correct application of cross slope reduces the need for side friction, while incorrect cross slope -
such as a crowned section in an ancient outercurve - increases the need for side friction.
Cross slope design codes all over the world are fundamentally based on the equilibrium
expressions above. Most codes are presenting design charts, showing what cross slope to use as
function of road curve radius and for given speeds. However, these design charts may differ,
depending on what value of the side friction supply factor fs that has been applied. In Sweden,
the used supply factor fs corresponds to the friction number between a good summer tyre (locked
wheel) and rain wet road in good condition, after deduction with 2/3 to add a safety margin
(VGU). The supply factor used in Sweden is a function of speed and is calculated as per
Formula 4.
f s 0.28 * e 0.0096*3.6*
Formula 4, The Side Friction Supply Factor used in Sweden [VGU]
In cold climate with icy winter roads and winter (Mud + Snow) tyres, such as in northern
Scandinavia, lower side friction supply factor fs may be relevant. As seen in Formula 3, a lower
fs results in a demand for higher superelevation for a given speed and radius. In the USA, the
factor fs are set to a speed-depending value where 95 % of the drivers slow down by 3 - 5 km/h
in the curve (NCHRP report 439).
The design chart for cross slope in 90 km/h curves in Sweden is based on a side friction supply
factor fs of 0.12, as given by Formula 4. (As per NCHRP report 439, American 90 km/h
highway curves are designed with a similar value - 0.13 - for the factor fs). The resulting
Swedish design chart is showed in Figure 4. Note that the Swedish code only allows certain
discrete values of cross slope. Since a curve with 1000 m radius may have 2.5 % or 4.0 % or 5.5
% cross slope and still fulfil “Good” standard (“God”, in Swedish), it is of course not hazardous
to have - let’s say - 3.2 % or 4.6 % cross slope in such a curve. A design chart that calls for
unnecessary cross slope adjustments of the existing cross slope (for example 4.6 %) just to meet
one of a few allowed discrete values, with no relevance what so ever to Newton´s laws of
physics, has of course extremely poor benefit/cost ratio when restoring old paved roads.
6. Transport Research Arena Europe 2010, Brussels
Figure 4 Cross Slope Design Chart for 90 km/h Roads in Sweden [VGU]
4. Testing How a Lane-change within a Curve Affects Travelled Curvature
This work is searching for a causal factor behind the excessive crash rates in sharp multiple lane
curves. The curve cross slope has been designed under the assumption that the travelled curved
path follows the road curvature. Could the main risk be that some vehicles experience much
higher lateral force, as their drivers make a quick lane-change within the curve (poor driving)?
Then this kind of curves should be designed with maximum allowed superelevation, in order to
compensate for the higher-than-considered lateral force.
To test the idea above, the curve was measured several times with a laser/inertial Profilograph.
The advanced Profilograph is normally used for accurate measurements of road alignment and of
road surface condition. Here the Profilograph was used to record travelled curvature during a
double lane-change, as compared to normal driving within the same lane through the whole
curve. Two types of double lane-changes were tested; one very smooth (over long distance) and
one quick and thus quite aggressive. All measurements were done at 90 km/h.
5. Travelled Curvature Peaked During the Quick Lane-Change
The Profilograph data is reported in Figure 5. In the reference-case, without changing lane (blue
line), the travelled curvature reached approximately 3 [km-1]. The two lane-changes both started
as the curvature reached its stationary level. The smooth lane-change (green line), the curvature
did not increase significantly. The quick double lane-change took about 55 m less than the
smooth lane-change. While being shorter, the quick lane-change resulted in travelled curvature
peaking up to about 4 [km-1]. This is some 35 % worse than indicated by the road curvature
itself, which is the curvature used when designing the cross slope. This result confirms that quick
lane-change can be a key factor behind the disproportionate crash rate seen in sharp multiple lane
curves.
Another observation is that the Skönsberg curvature (= 1000 / Radius) reach values of about 3
[km-1] already without lane-change. This corresponds to such sharp radius as 300 – 350 m.
Already a radius of 350 m is on the edge of being unacceptably sharp for a 90 km/h road, when
comparing with the design tolerances also for “poor” standard (“låg” standard in Swedish) given
in Figure 4. Obviously the current speed limit of 90 km/h should be reduced at least when the
7. Transport Research Arena Europe 2010, Brussels
road is slippery, since the curve is sharper than allowed when designing 90 km/h curves in
Sweden.
Figure 5 Travelled Curvature With/Without a Double Lane-Change
The measured combination of cross slope and curvature was analyzed in a new chart that was
developed in the Roadex project (Granlund, 2008). This chart is basically a transform of the
cross slope design chart in Figure 4. Cross slope rates are given as function of curve radius in the
traditional design chart. An important difference with the new chart, is that cross slope rates are
given as function of curvature (=1000/Radius). This makes it possible to plot data measured both
from curves and from straight sections, where the radius goes into +/- infinity. Furthermore a
copy of the chart has also been “flipped”, so data from both innercurves (+) and outercurves (-)
can be investigated in the same resulting chart. The chart in Figure 6 show tolerance boxes for 90
km/h; properly banked curves have all their data within the green boxes. Each data point
corresponds to average values over 1 m. The plotted data reveal that the Skönsberg curve is not
only too sharp, but also too flat even when driving without lane-change. Clearly, the Skönsberg
curve would be safer if redesigned with maximum allowed cross slope of - 5.5 % in Sweden.
Figure 6 Paired Cross Slope and Curvature Data from the Southbound Fast Lane
8. Transport Research Arena Europe 2010, Brussels
6. Conclusions and Recommendations
Curve cross slope design codes are based on analysis of cornering forces acting on AASHO’s
point-mass model of a vehicle. A systematic problem with skid accidents on multiple lane curves
has been identified. Current road design practise approximates the vehicle travelled path (and
thus lateral force) by the road curvature, which is reasonable on small roads. On multiple lane
roads however, many drivers are changing lane also in sharp curves. When shifting lane quickly,
the vehicle experience a transient “curve radius” much sharper than indicated by the road curve
radius. This can yield higher lateral force than the road design code have considered. Results in
this work show that in a sharp curve, a lane-changing vehicle was exposed to 35 % higher lateral
force than given by the road curvature itself. Without considering this driving mode when
designing the curve, the selected superelevation may be insufficient - when the road is slippery -
to outbalance the cornering force.
Curve design codes should be revised to include the following rule by thumb:
-Sharp curves on multiple lane roads with high speed traffic should be designed with
maximum allowed cross slope.
However, maximized cross slope is only recommended for sharp curves. In soft curves,
excessive superelevation may be detrimental in the critical final moment of the double lane-shift.
When applying enhanced cross slope in sharp multiple lane curves, the maximum allowed
superelevation values (for example 12 % in the USA and 8 % in Norway) should not be
exceeded.
The geometry of existing curves can efficiently be evaluated with a new type of chart, where
measured data for cross slope is paired with data for curvature (see Figure 6). The new chart
gives clear information on if the road has too sharp or improperly banked curves. This
information should be used to decide speed limit reduction, posting warning signs (preferably
using intelligent sensors recording vehicle speed and road slipperiness), intensified friction
maintenance and curve redesign such as increasing the cross slope or straightening the curve.
In order to improve the Benefit-to-Cost ratio for road renovation, the design chart for cross slope
used in Sweden should be revised. It is of no value to demand a few fixed cross slope values;
target cross slopes should be expressed as a range instead. For highway speed stability reasons,
the maximum allowed superelevation in Swedish hairpin curves should be raised into 8 %, as in
Norway and in “winter-white” areas of the USA too (see NCHRP 439).
The Profilograph measurements in the E4 Skönsberg Curve show that a smooth double lane-
change resulted in lateral forces similar to those experienced during cornering without lane-
change. The quick lane-change resulted in 35 % higher lateral force in the sharp curve. (Tests not
showed here, made in a smoother curve on highway E4, resulted in an even larger relative
increase of lateral force but with absolute values smaller than in the sharp Skönsberg curve).
These results illustrate the risk with making quick lane-changes. There is a need for improved
education of motor vehicle drivers, making them aware of the importance of avoiding quick
lane-changes in curved sections on multiple lane roads.
9. Transport Research Arena Europe 2010, Brussels
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