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.

1. 1´st European Pavement Management Systems Conference, Budapest 2000
Granlund, J. (2000). CAD/CAM pavement maintenance actions - An efficient method to reduce human whole
body vibrations
CAD/CAM pavement maintenance actions
- An efficient method to reduce human whole body vibrations
Johan Granlund, M.Sc. (Civil Eng.)
Pavement Engineering Division, Consulting Services Directorate
Swedish National Road Administration
781 87 BORLANGE, SWEDEN
For rough road sections, traditional pavement maintenance actions such as the 2’’ overlay is
quite efficient in reducing ground vibrations, vehicle body noise, rolling resistance and re-
establishing bearing capacity as well as a nice looking surface. The overlay is also often effi-
cient in reducing vertical and horizontal whole body vibrations (WBV) in vehicle cabs, inter-
fering with vehicle occupant’s comfort, activities and health as described in ISO 2631-1.
Shocks must be limited with respect to injured patients in high-speed ambulance transports,
while vibration dosis (time * intensity) limits must comply with occupational health exposure
limits, regarding professional truck drivers. New knowledge has revealed that also rotational
vibrations roll, pitch and yaw cause human physiological/pathological and behavioral re-
sponses. Therefore those vibration modes were incorporated in the 1997 revision of ISO
2631-1. To reduce these vibrations, focus needs to be set also on road slopes and crossfall.
Extremely low frequency vertical vibrations - 0,1 to 0,63 Hz - cause motion sickness, which is
a severe problem during emergency ambulance transports. No vehicle suspension can reduce
these random and non-periodic slow vibrations when they are caused by a poor road rough-
ness profile. This document provide an introduction to the Swedish specification of a geomet-
rical pavement model, developed especially for use in road maintenance projects where Com-
puter Aided Design - and also Computer Aided Manufacturing - will be used. Use of the new
specification gives the prerequisites needed to supervise crossfall variations and long-wave
roughness. This in turn leads to the possibility to - within the budget frame of the road main-
tenance project - optimize actions to reduce road defects that causes unnecessary human
whole body vibrations.
Introduction
Everybody knows that road roughness causes cab vibrations when riding in highway speeds.
Attempts to measure vehicle vibrations have also been made ever since the introduction of the
automobile [1]. Today most road authorities measure a substitute for vertical cab vibrations,
which under the acronym IRI (International Roughness Index) is used as a basic input to
PMS-activities. From a recent Swedish research project ”Whole body vibrations while riding
rough roads” [2], it has been concluded that the IRI correlates quite well with the impact on
the human. The most important reasons for the absence of a full match though, is that:
I. ”the golden car” used in the IRI-calculation doesn’t pay respect to human vibration
frequency sensitivity, as described by the ISO 2631 filters Wk and Wf [2].
II. as roughness increases, bumps and other surface damages become more visible. This
increases the drivers ability to avoid them by making lateral vehicle movements (while
profilometers measuring IRI drives in the wheeltracks with very little lateral wander),
III. IRI is an estimate of vertical chassi vibration only, to compare with the 12 (!) WBV
modes affecting humans strongly under seated road transportations [6],
IV. in Sweden, the IRI calculation is made only with respect to the roughness profile in
the outer wheeltrack, while real cab vibrations of course relates to both the inner and
the outer track roughness.

2. 1´st European Pavement Management Systems Conference, Budapest 2000
Granlund, J. (2000). CAD/CAM pavement maintenance actions - An efficient method to reduce human whole
body vibrations
The project also concluded road roughness (including long wave road roughness and large
variance of crossfall) as being a severe threat to road user’s health1
. This conclusion supports
the findings of the US FHWA R&D program ”Ride Quality of Commercial Motor Vehicles
and the Impact on Truck Driver Performance” (1977 - 1982) [3]. Recent research, biodynamic
as well as physiological experiments, have shown that seated whole body vibrations (WBV)
exposure can affect the spine by mechanical overloading and excessive muscular fatigue, sup-
porting the epidemiological findings of a possible causal role of WBV in the development of
(low) back troubles. The relevance of this problem is stressed since the vibration exposure in
trucks often exceeds the limits in the amended proposal to European Directive, regarding al-
lowable human vibration exposure [4]. This paper gives a brief description of a new specifica-
tion of a geometrical pavement model [5], developed especially to give the prerequisites
needed to supervise crossfall and long-wave roughness. Use of this model will reduce WBV,
thereby preventing health problems among professional drivers as well as motion sickness
and harmful high-frequency vibrations among injured patients in ambulances at high speed.
Use of the geometric pavement model
Figure 1 displays process steps for CAD / CAM pavement maintenance actions.
Figure 1 Flow chart; from survey of a rough road section - to a smooth pavement
Survey parameters
• Roughness profile (incl. slopes)
• Crossection (incl. crossfall)
• Horizontalcurvature
• Roadvideo, displaying large surface damages (cracks etc.) and supporting proper design of
crossfall variations
In figure 2 the roughness profile (top) and a crossection (bottom) from a pavement mainte-
nance project, designed in SNRA´s CAD-software ”Fill and mill”, is displayed. The volumes
and min / max thickness of filling and milling can also be presented by the software.
1
According to the WHO definition from 1946, health means total comfort; physically as well as mental, and not
only momentan absence of sickness and handicap.
Geometric
pavement
model
Computer aided
geometric pave-
ment design
Road surface
survey
Workplan
Computer aided
manufacturing
Pavement with geometry
corresponding to the design,
manufactured under safe
conditions and with minimal
use of nature´s resources

3. 1´st European Pavement Management Systems Conference, Budapest 2000
Granlund, J. (2000). CAD/CAM pavement maintenance actions - An efficient method to reduce human whole
body vibrations
Basic principle for tolerances
The superior demand is that every survey result must be within specified limits with the prob-
ability 95,0 percent.
Figure 2 Geometric pavement model, used in SNRA´s CAD-software ”Fill and mill”
Roughness profile
Each value shall show the relative level difference between the actual section and each of the
sections 5, 10, 15 and 20 meters in front and the sections 5, 10, 15 and 20 m behind. The lon-
gitudinal resolution is 5 m, while the vertical resolution is 1 mm. The tolerance in height is
5,0 mm, and in plane 100 mm (relative a selected reference, for instance the road marking).
Short-wave (λ< 10 m) roughness
If at least 80 kg/m2
wearing course is used, roughness with up to approx. 10 m wavelength
and amplitudes less than 1 inch will be repaired through the normal thickness variations /
adoptions of the course. If less (thinner) wearing course is to be used on a surface with short-
wave roughness damages, full length milling or filling is needed before paving the wearing
course. If we only follow these simple guidelines and manage the manufacturing properly,
short-wave roughness will be eliminated.
Long-wave (10 < λ< 350 m) roughness
Motion sickness, identified as a severe problem during emergency ambulance transports, is
caused by vibrations 0,1 - 0,63 Hz [7]. The human is absolutely most prone at 0,16 - 0,25 Hz.

4. 1´st European Pavement Management Systems Conference, Budapest 2000
Granlund, J. (2000). CAD/CAM pavement maintenance actions - An efficient method to reduce human whole
body vibrations
Vehicle suspension isn’t active at any of these low frequencies, making the entire vehicle act-
ing as a rigid body. Therefore the basic relation between speed, wavelength and vibration fre-
quency can be used; λ = v/f. At the speed 35 m/s (126 km/h) the frequency 0,1 Hz corre-
sponds to the wavelength 35 / 0,1 = 350 m. This leads to the conclusion that surface undula-
tions with wavelengths up to 350 m can cause large impacts on ride quality while riding in
highway speeds, and that this constitutes the upper limit for roughness wavelengths.
The Swedish physician Harry Nyquist stated a sampling theorem, which say that one can’t
derive components with frequencies above half the sampling frequency from any signal (in
this case: the roughness profile). In order to derive components down to 10-m length, we
therefore need to sample at 5-m interval. This is also a practical limit; we don’t design
changes in the paver´s settings more often than this, since the reaction length of the floating
screed typically is somewhat above 5 m. The high-frequency components above the Nyquist
frequency (half the sampling frequency) can through ”aliasing” cause a distorted picture of
the low frequency components, whom we are measuring. The aliasing phenomenon is usually
handled by use of ”anti-aliasing” filters. In our case we handle the problem by using a high-
frequency profiler2
and representing each 5 m value of the roughness profile in the model by
averaged signals from 16 kHz sampling (at operating speeds resulting in sampling at millime-
tre interval) over the 5 meters, instead of representing the 5 m sample values with single
”shots”.
With this method it is possible to produce a roughness profile, consisting of wavelengths over
10 m from the measured road.
Crossection
The crossection3
is represented by values (transversal spacing max 2,5 dm), averaged from
samples taken at max 1 dm longitudinal interval over a distance 2,5 m in front of, and 2,5 m
behind, the section in question. The crossfall variations is surveyed with the same longitudinal
resolution as the roughness profile; 5 m. Each value in the section represents the level, related
to the roughness profile level of the section with a resolution of 1 mm.
Tolerance
• Level, relative to the roughness profile: ± 5,0 mm.
• Transversal position, relative to the roughness profile position: ± 100 mm.
Horizontalcurvature
The roadvideo, measured crossection and horisontalcurvature (radius) support design of
crosslope and its variation. The horizontal curvature radius is represented by values averaged
from 20-meter length. The resolution varies from 10 to 1 000 m, depending on the radius
magnitude. Straight sections are reported with radius 99 999 m. The tolerance is ± 20 % of the
magnitude.
Visual road environment
The road is recorded on videotape (VHS), in order to support the designer to relate the meas-
urements to the roadside. Also the road surface (orthogonal projection) is filmed, in order to
display larger surface damages, crocodile cracking etc. The videotapes display length posi-
tion, with a resolution of 1 m.
2
SNRA Pavement Engineering Division operates a Profilograph, manufactured by Greenwood Eng. (DK)
3
Horisontalcurves needs special attention, when establishing the geometrical model.

5. 1´st European Pavement Management Systems Conference, Budapest 2000
Granlund, J. (2000). CAD/CAM pavement maintenance actions - An efficient method to reduce human whole
body vibrations
References
[1] Dana, H.J. (1930). Formation of Washboards in Gravel Highways. Highway Research
Board, Proceeding
[2] Ahlin, K., Granlund, J. & Lundstrom, R. (2000). Whole body vibrations while riding
rough roads. (Report in 3 parts, in Swedish only). Part I: Ingemansson Technology AB, Re-
port no. S-13542-r-A (www.ingemansson.com). Part II: The National Institute for Working
Life, NIWL Publ. no. 2000:1 (umetech.niwl.se). Part III: Swedish National Road Administra-
tion, VV Publ. no 2000:31 (www.vv.se).
[3] Gillespie, T.D. et al. (1982). Truck Cab Vibrations and Highway Safety. Highway Safety
Research Institute, University of Michigan. FHWA report RD-82/093
[4] Bovenzi, M. & Hulshof, C.T.J. (1999). An updated review of epidemiologic studies on the
relationship between exposure to whole-body vibration and low back pain (1986-1997). Int
Arch Occup Environ Health (1999) 72:351-365
[5] Granlund, J. & Lang, J. (2000). A geometric pavement model for Computer Aided Design
of pavement maintenance actions. (In both Swedish and English). Swedish National Road
Administration, VV Publ. no 1999:100 and 1999:100 E (www.vv.se).
[6] ISO 2631-1 (1997) Mechanical vibration and shock – Evaluation of human exposure to
whole-body vibration – Part 1: General requirements.
[7] ISO 2631-3 (1985) Mechanical vibration and shock – Evaluation of human exposure to
whole-body vibration – Part 3: Human impact from vertical whole-body vibration in the z-
direction in the frequency range 0.1 – 0.63 Hz.

6. 1´st European Pavement Management Systems Conference, Budapest 2000
Granlund, J. (2000). CAD/CAM pavement maintenance actions - An efficient method to reduce human whole
body vibrations
The figure above shows the relationship between IRI-response and human comfort / health
frequency sensitivity weighted vertical cab vibration, while riding ”The Golden Car” (the
filter used for the IRI-calculation) over a certain road roughness amplitude at different
wavelengths and speeds. Values exceeding 0,16 on the z-axle occurs under conditions at
which the IRI-response underestimates the human response.
The figure above presents basicentric axles of the12 dominant vibration modes affecting
persons seated in road vehicles. As a comparison, IRI is an estimate of vertical chassi
vibration. Despite this, IRI correlates quite well also with pitch generated fore-aft movements.