This document discusses various aspects of vertical alignment in transportation engineering. It describes how vertical alignment specifies the elevation of points along a roadway based on safety, comfort, drainage needs. Vertical curves are used to transition between different roadway grades and can be crest or sag curves. The coordination of vertical and horizontal alignment is also discussed to ensure driver safety and aesthetics. Maximum and minimum grades, as well as critical lengths of grades, are addressed based on truck performance.
A highway pavement is a structure consisting of superimposed layers of processed materials above the natural soil sub-grade, whose primary function is to distribute the applied vehicle loads to the sub-grade. The pavement structure should be able to provide a surface of acceptable riding quality, adequate skid resistance, favorable light reflecting characteristics, and low noise pollution. The ultimate aim is to ensure that the transmitted stresses due to wheel load are sufficiently reduced, so that they will not exceed bearing capacity of the sub-grade. Two types of pavements are generally recognized as serving this purpose, namely flexible pavements and rigid pavements.
Get an overview of pavement types, layers, and their functions, and pavement failures as Improper design of pavements leads to early failure of pavements affecting the riding quality.
Pavements form the basic supporting structure in highway transportation. Each layer of pavement has a multitude of functions to perform which has to be duly considered during the design process. Different types of pavements can be adopted depending upon the traffic requirements.
Transition curve and Super-elevation
Transition Curve
Objectives of Transition Curve
Properties Of Transition Curve
Types Of Transition Curve
Length Of Transition Curve
Superelevation
Objective of providing superelevation
Advantages of providing superelevation
Superelevation Formula
Numerical
A highway pavement is a structure consisting of superimposed layers of processed materials above the natural soil sub-grade, whose primary function is to distribute the applied vehicle loads to the sub-grade. The pavement structure should be able to provide a surface of acceptable riding quality, adequate skid resistance, favorable light reflecting characteristics, and low noise pollution. The ultimate aim is to ensure that the transmitted stresses due to wheel load are sufficiently reduced, so that they will not exceed bearing capacity of the sub-grade. Two types of pavements are generally recognized as serving this purpose, namely flexible pavements and rigid pavements.
Get an overview of pavement types, layers, and their functions, and pavement failures as Improper design of pavements leads to early failure of pavements affecting the riding quality.
Pavements form the basic supporting structure in highway transportation. Each layer of pavement has a multitude of functions to perform which has to be duly considered during the design process. Different types of pavements can be adopted depending upon the traffic requirements.
Transition curve and Super-elevation
Transition Curve
Objectives of Transition Curve
Properties Of Transition Curve
Types Of Transition Curve
Length Of Transition Curve
Superelevation
Objective of providing superelevation
Advantages of providing superelevation
Superelevation Formula
Numerical
Highway planning and alignment: Different modes of transportation – historical Development of road construction- Highway Development in India –Classification of roads- Road pattern
– Highway planning in India- Highway alignment - Engineering Surveys for alignment – Highway Project- Important Transport/Highway related agencies in India. PMGSY project.
Introduction about IRC, NRRDA
topics which are discussed in this slide are,
1) pavement and requirement for pavement design.
2) Rigid and flexible pavement .
3) pavement design method.
Highway Engineering for BE Civil Engineering Students
History of Roads in India, IRC, CRRI, Classification of Roads, Three 20 year Road Development Plans, Road patterns, Accident Studies,
The clear distance ahead of vehicle which is visible to the driver is known as sight distance
The minimum distance within which a driver can safely stop his vehicle without any collision with some vehicle, animal or any other object is known as stopping sight distance.
Alignment: The position or the layout of the central line of the highway on the ground is called the alignment.
Highway Alignment includes both
a) Horizontal alignment includes straight and curved paths, the deviations and horizontal curves.
b) Vertical alignment includes changes in level, gradients and vertical curves.
Often changes in the direction are necessitated in highway alignment due to various reasons such as topographic considerations, obligatory points.
The geometric design elements pertaining to horizontal alignment of highway should consider safe and comfortable movement of vehicles at the given design speed of the highway.
It is therefore necessary to avoid sudden changes in direction with sharp curves or reverse curves which could not be safely and conveniently negotiated by the vehicles at design speed.
Improper design of horizontal alignment of roads would necessitate speed changes resulting m higher accident rate and increase in vehicle operation cost.
Highway planning and alignment: Different modes of transportation – historical Development of road construction- Highway Development in India –Classification of roads- Road pattern
– Highway planning in India- Highway alignment - Engineering Surveys for alignment – Highway Project- Important Transport/Highway related agencies in India. PMGSY project.
Introduction about IRC, NRRDA
topics which are discussed in this slide are,
1) pavement and requirement for pavement design.
2) Rigid and flexible pavement .
3) pavement design method.
Highway Engineering for BE Civil Engineering Students
History of Roads in India, IRC, CRRI, Classification of Roads, Three 20 year Road Development Plans, Road patterns, Accident Studies,
The clear distance ahead of vehicle which is visible to the driver is known as sight distance
The minimum distance within which a driver can safely stop his vehicle without any collision with some vehicle, animal or any other object is known as stopping sight distance.
Alignment: The position or the layout of the central line of the highway on the ground is called the alignment.
Highway Alignment includes both
a) Horizontal alignment includes straight and curved paths, the deviations and horizontal curves.
b) Vertical alignment includes changes in level, gradients and vertical curves.
Often changes in the direction are necessitated in highway alignment due to various reasons such as topographic considerations, obligatory points.
The geometric design elements pertaining to horizontal alignment of highway should consider safe and comfortable movement of vehicles at the given design speed of the highway.
It is therefore necessary to avoid sudden changes in direction with sharp curves or reverse curves which could not be safely and conveniently negotiated by the vehicles at design speed.
Improper design of horizontal alignment of roads would necessitate speed changes resulting m higher accident rate and increase in vehicle operation cost.
The geometric design of roads is the branch of highway engineering concerned with the positioning of the physical elements of the roadway according to standards and constraints. The basic objectives in geometric design are to optimize efficiency and safety while minimizing cost and environmental damage. Geometric design also affects an emerging fifth objective called "livability," which is defined as designing roads to foster broader community goals, including providing access to employment, schools, businesses and residences, accommodate a range of travel modes such as walking, bicycling, transit, and automobiles, and minimizing fuel use, emissions and environmental damage.
Geometric roadway design can be broken into three main parts: alignment, profile, and cross-section. Combined, they provide a three-dimensional layout for a roadway.
The alignment is the route of the road, defined as a series of horizontal tangents and curves.
The profile is the vertical aspect of the road, including crest and sag curves, and the straight grade lines connecting them.
The cross section shows the position and number of vehicle and bicycle lanes and sidewalks, along with their cross slope or banking. Cross sections also show drainage features, pavement structure and other items outside the category of geometric design.
#source:
1. Highway Engineering by: Khanna & Justo
2. Wikipedia
TRAFFIC FLOW ANALYSIS & EFFICIENCY OF GEOMETRIC DESIGN OF A T-INTERSECTION, A...IAEME Publication
The major concern for a Highway Engineer in any road network system is an intersection.The heterogeneous traffic is more diverse in nature due to lane changing and lack of lane discipline characteristics of drivers’ in India. Our research is intended to check the efficiency and control of flow of traffic at “Tara Wala Pul (Bridge)-T intersection” , point out flaws (if any) in the geometric design and work out the possible solutions.
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Content- Design of horizontal alignment: horizontal curves, design of super elevation and its provision, radius at horizontal curves, widening of pavements at horizontal curves, analysis of transition curves.
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Explore the innovative world of trenchless pipe repair with our comprehensive guide, "The Benefits and Techniques of Trenchless Pipe Repair." This document delves into the modern methods of repairing underground pipes without the need for extensive excavation, highlighting the numerous advantages and the latest techniques used in the industry.
Learn about the cost savings, reduced environmental impact, and minimal disruption associated with trenchless technology. Discover detailed explanations of popular techniques such as pipe bursting, cured-in-place pipe (CIPP) lining, and directional drilling. Understand how these methods can be applied to various types of infrastructure, from residential plumbing to large-scale municipal systems.
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Water scarcity is the lack of fresh water resources to meet the standard water demand. There are two type of water scarcity. One is physical. The other is economic water scarcity.
CFD Simulation of By-pass Flow in a HRSG module by R&R Consult.pptxR&R Consult
CFD analysis is incredibly effective at solving mysteries and improving the performance of complex systems!
Here's a great example: At a large natural gas-fired power plant, where they use waste heat to generate steam and energy, they were puzzled that their boiler wasn't producing as much steam as expected.
R&R and Tetra Engineering Group Inc. were asked to solve the issue with reduced steam production.
An inspection had shown that a significant amount of hot flue gas was bypassing the boiler tubes, where the heat was supposed to be transferred.
R&R Consult conducted a CFD analysis, which revealed that 6.3% of the flue gas was bypassing the boiler tubes without transferring heat. The analysis also showed that the flue gas was instead being directed along the sides of the boiler and between the modules that were supposed to capture the heat. This was the cause of the reduced performance.
Based on our results, Tetra Engineering installed covering plates to reduce the bypass flow. This improved the boiler's performance and increased electricity production.
It is always satisfying when we can help solve complex challenges like this. Do your systems also need a check-up or optimization? Give us a call!
Work done in cooperation with James Malloy and David Moelling from Tetra Engineering.
More examples of our work https://www.r-r-consult.dk/en/cases-en/
Overview of the fundamental roles in Hydropower generation and the components involved in wider Electrical Engineering.
This paper presents the design and construction of hydroelectric dams from the hydrologist’s survey of the valley before construction, all aspects and involved disciplines, fluid dynamics, structural engineering, generation and mains frequency regulation to the very transmission of power through the network in the United Kingdom.
Author: Robbie Edward Sayers
Collaborators and co editors: Charlie Sims and Connor Healey.
(C) 2024 Robbie E. Sayers
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2. Vertical Alignment
Vertical alignment specifies the elevation of points along roadway.
The elevation of these roadway points are usually determined by the
need to provide an acceptable level of driver safety, driver comfort,
cut to fill and proper drainage (form rainfall runoff).
A primary concern in vertical alignment is establishing the transition
of roadway elevations between two grades. This transition is
achieved by means of a vertical curve.
Each roadway is uniquely defined by stationing (which is measured
along a horizontal plane) and elevation.
3. Vertical Alignment
Vertical curve can be
broadly classified into
• Crest Vertical Curves
• Sag Vertical Curves
The proper relationships
between vertical and
horizontal curvature result
in an aesthetic and easy-
to-drive facility.
Truck
5. Vertical Alignment
• Horizontal and vertical alignment should not be
designed independently. They complement each
other and poor design combinations can spoil the
good points and aggravate the deficiencies of
each. Properly coordinated horizontal and vertical
alignment can enhance community values,
increase utility and safety, encourage uniform
speed, and improve appearance.
• Sharp horizontal curvature should not be
introduced near bottom of steep grade near the
low point of a pronounced sag vertical curve
– Horizontal curves appear distorted
– Vehicle speeds (esp. trucks) are highest at the
bottom of a sag vertical curve
– Can result in erratic motion
Truck
6. Coordination of Vertical and Horizontal
Alignment
• Curvature and grade should
be in proper balance
– Avoid
• Excessive curvature to achieve
flat grades
• Excessive grades to achieve flat
curvature
• Vertical curvature should be
coordinated with horizontal
• Sharp horizontal curvature should
not be introduced at or near the
top of a pronounced crest vertical
curve
– Drivers may not perceive
change in horizontal alignment
esp. at night
Truck
7. Coordination of Vertical and Horizontal
Alignment
• On two-lane roads when passing
is allowed, need to consider
provision of passing lanes
– Difficult to accommodate with
certain arrangements of horizontal
and vertical curvature
– need long tangent sections to assure
sufficient passing sight distance
Truck
8. Coordination of Vertical and Horizontal
Alignment
• At intersections where sight distance
needs to be accommodated, both
horizontal and vertical curves should be
as flat as practical
• In residential areas, alignment should
minimize nuisance to neighborhood
– Depressed highways are less visible
– Depressed highways produce less noise
– Horizontal alignments can increase the buffer
zone between roadway and cluster of homes
Truck
9. Coordination of Vertical and Horizontal
Alignment
• When possible alignment should
enhance scenic views of the natural
and manmade environment
– Highway should lead into not away from
outstanding views
– Fall towards features of interest at low
elevation
– Rise towards features best seen from
below or in line against the sky
Truck
10. Coordination of Horizontal
and Vertical Alignment
• Coordination of horizontal and vertical
alignment should begin with
preliminary design
• Easier to make adjustments at this
stage
• Designer should study long,
continuous stretches of highway in
both plan and profile and visualize the
whole in three dimensions
12. • Should be consistent with the
topography
• Preserve developed properties
along the road
• Incorporate community values
• Follow natural contours of the
land
Coordination of Horizontal and Vertical
AlignmentTruck
13. Good Coordination of Horizontal and
Vertical Alignment
• Does not affect
aesthetic, scenic,
historic, and
cultural resources
along the way
• Enhances attractive
scenic views
– Rivers
– Rock formations
– Parks
– Historic sites
– Outstanding
buildings
Truck
14.
15.
16.
17.
18.
19.
20. Vertical Curves
• Connect roadway grades
(tangents)
• Grade (rise over run)
– 10% grade increases 10' vertically
for every 100 ' horizontal
Truck
21. Vertical Curves
Ascending grade:
– Frequency of
collisions increases
significantly when
vehicles traveling
more than 10 mph
below the average
traffic speed are
present in the
traffic stream
Truck
22. Example
• If a highway with
traffic normally
running at 65 mph
has an inclined
section with a 3%
grade, what is the
maximum length
of grade that can
be used before the
speed of the larger
vehicles is reduced
to 55 mph?
Truck
24. Continuity of Vertical
Curve
• Continuity of
forms
For vertical curves continuity
of form is not a problem.
There is no sudden break in
grade at the PC or PT since
the parabolic curve provides a
gradual transition in grade
• Continuity of
scale
Continuity of scale relates to
the relative lengths of the
tangent and curves
From an esthetic point of view, one of the goal in alignment design
is to achieve a continuous alignment. Continuity is desirable so
that the road fit the terrain, does not have a jarring aspect and
present a path which is easy to follow
25.
26. Climbing Lanes
• When flatter grades cannot be
accommodated, consider climbing lane
when all 3 of the following criteria are met
(AASHTO):
– Upgrade traffic flow rate in excess of 200
vehicles per hour.
– Upgrade truck flow rate in excess of 20
vehicles per hour.
– One of the following conditions exists:
• A 15 km/h or greater speed reduction is expected
for a typical heavy truck.
• Level-of-service E or F exists on the grade.
• A reduction of two or more levels of service is
experienced when moving from the approach
segment to the grade.
Truck
27. Critical Lengths of Grade
for Design
• Maximum length of a designated upgrade upon
which a loaded truck can operate without an
unreasonable reduction in speed,
• For a given grade, lengths less than critical results in
acceptable operation in the desired range of speeds.
where the desired freedom of operation is to be
maintained on grades longer than critical, design
adjustments such as change in location to reduce grades
or addition of extra lanes should be made.
• A separate climbing lane exclusively for slow moving
vehicles is preferred to the addition of an extra lane
carrying mixed traffic. The large speed differential
between trucks and passenger cars traveling up grade in
the same lanes greatly increases the accident potential.
28. Critical Lengths of Grade
for Design
Design values for critical lengths of grade were established
based on the size and power of a representative truck or
truck combination, the gradability data for this vehicle, the
speed at entrance to critical length of grade, and the
minimum speed on the grade, below which interference to
following vehicles is considered unreasonable.
A loaded truck with a weight-power ratio of approximately
400 was used as a nationally representative truck. The
speed of vehicles beginning at uphill climb approximates
the average running speed of the highway.
On most of the arterial streets where the running speed will
be 40 mph or less, truck speeds of 20 to 35 mph are not
unreasonably annoying to following drivers. The developed
control basis for determining critical length of grades and
the need for climbing lanes is normally a reduction of 15
miles per hour in speed of trucks below the average running
speed.
29. Descending Grades
• Problem is increased speeds and loss of control for
heavy trucks
• Runaway vehicle ramps are often designed and
included at critical locations along the grade
• Ramps placed before each turn that cannot be
negotiated at runaway speeds
• Ramps should also be placed along straight
stretches of roadway, wherever unreasonable speeds
might be obtained
• Ramps located on the right side of the road when
possible
• Have detrimental effect on capacity and safety on
urban facilities with high traffic volumes and
numerous heavy trucks. Although criteria are not
established for these conditions., in some cases
consideration should be given to providing a truck
lane for downhill traffic.
Truck
30. Maximum Grades
Criteria for maximum grades are based
mainly on studies of the operating
characteristics of typical heavy trucks.
• Passenger vehicles can easily negotiate 4
to 5% grade without appreciable loss in
power
• Upgrades: trucks average 7% decrease
in speed
• Downgrades: trucks average speed
increase 5%
Truck
31. Minimum Grades
• Minimum grades are primarily related to the need for
adequate drainage.
• For uncurbed pavements that are adequately crowned to
drain laterally, relatively flat or even level profile grades
may be used.
• With curbed pavement, the minimum longitudinal grade
in usual cases should be 0.5 percent.
• With a high-type pavement accurately crowned on a firm
subgrade, a longitudinal grade of about 0.3 percent may
be used.
• Even on uncurbed pavements, it is desirable to provide a
minimum of about 0.3 percent longitudinal grade
because the lateral crown slope originally constructed
may subsequently be reduced as a result of irregular
swell, consolidation, maintenance operations or
resurfacing.
• Equalizing situations such as lakebeds or slough areas a
0.0 % grade may be used.
Truck
32. Minimum Ditch Grades
• Special attention should be directed to
minimum ditch grades in areas of expansive
soils.
• These areas will be identified in the soils design.
Any pounding of water has a very detrimental
effect on the subgrade.
• To ensure continuing flow, ditch grades should
be sloped at least 0.3 percent -- preferably 0.5
percent or steeper.
• This may require some special warping of ditch
grades when the roadway profile cannot be
adjusted accordingly.
33. • The “roller coaster” or “ hidden –dip” type profile
generally occur on relatively straight horizontal
alignment where the roadway profile closely follows a
rolling natural ground line.
• A sky line horizon at crest disappear into the sky and can
be disconcerting to the driver. It would be appealing to
have the view above the crest backed by a back drop of
landscape.
• A profile on a pronounced crest along a horizontal curve,
particularly in flat terrain, tends to produce in a
foreshortened view a disturbingly awkward appearance.
Use of longer and flatter approach gradients, coupled with
special gradient and planting on inside of the curve may
reduce the undesirable effect.
35. Vertical Curves
• Crest – stopping, or passing sight
distance controls
• Sag – headlight/SSD distance,
comfort, drainage and appearance
control
• Green Book vertical curves defined by
K = L/A = length of vertical
curve/difference in grades (in percent)
= length to change one percent in
grade
Truck
36. Parabola
y = ax2
+ bx + c
Where:
y = roadway elevation at distance x
x = distance from beginning of
vertical curve
a = G2 – G1
L
b = G1
c = elevation of PVC
Vertical Curve Equations
Truck
37. Vertical Curve AASHTO Controls
(Crest)
• Minimum length must provide stopping
sight distance S
• Two situations (both assume h1=3.5’
and h2=2.0’)
Truck
40. Example: Try SSD > L,
Design speed is 60 mph
G1 = 3% and G2 = -1%,
what is L?
(Assume grade = 0% for SSD)
SSD = 570feet ( see: Table 3.4 of text)
Lmin = 2 (570’) – 2158’ = 600.5’
|(-1-3)|
S < L, so it doesn’t match condition
Truck
41. Example: Assume SSD < L,
Design speed is 60 mph
G1 = 3% and G2 = -1%,
what is L?
Assuming average grade = 0%
SSD = 570 feet - ( Table 3.4 of text)
Lmin = |(-3 - 1)| (570 ft)2
= 602 ft
2158
SSD < L, equation matches condition
Truck
42. Evaluation of example:
• The AASHTO SSD distance equations
provided the same design length from
either equation in this special case.
(600 compared to 602 - this is not
typical)
• Garber and Hoel recommend using the
most critical grade of - 1% for SSD
computation.
– Resulting SSD would be: d = 573 ft
– Resulting minimum curve: L = 608 ft
• Difference between 602 and 608 is too
small to worry about
Truck
43. Text example : g1 = + 3% g2 = -3%
Design speed of 60 mph
If SSD = 570’ (AASHTO – no grade consideration)
Resulting minimum curve: L = 903 ft (S < L)
Consider grade per Garber and Hoel
SSD, using - 3% grade, = 595’
Resulting minimum curve L = 984 ft
Truck
44. Assessment of Grade
Adjustment
If sight distance is less than curve length, the driver
will be on an upgrade a greater portion of the
distance than on a down grade
(for eye ht = 3.5’ and object ht = 2.0 ft, 68% of the
distance between eye and object will be on + grade.)
For crest vertical curve, selecting a curve length
based on down grade SSD may produce an overly
conservative design length.
Truck
45. AASHTO design tables
• Vertical curve length can also be
found in design tables
L = K *A
Where
K = length of curve per percent
algebraic difference in intersecting
grade
Charts from Green Book
Truck
48. Vertical Curve AASHTO
Controls (Crest)
Since you do not at first know L, try
one of these equations and compare
to requirement, or use L = KA (see
tables and graphs in Green Book for
a given A and design speed)
Note min. L(ft) = 3V(mph) – Why?
Truck
49. Chart vs computed
From chart
V = 60 mph K = 151 ft / % change
For g1 = 3 g2 = - 1
A = | -1 – 3 | = 4
L = ( K * A) = 151 * 4 = 604
Truck
50. Sag Vertical Curves
• Sight distance is governed by
nighttime conditions
– Distance of curve illuminated by
headlights need to be considered
• Driver comfort
• Drainage
• General appearance
Truck
51. Vertical Curve AASHTO
Controls (Sag)
Headlight Illumination sight distance
S < L: L = AS2
400 + (3.5 * S)
S > L: L = 2S – (400 + 3.5S)
A
Truck
52. Vertical Curve AASHTO Control
(Sag)
• For driver comfort use:
L > AV2
46.5
(limits g force to 1 fps/s)
• To consider general appearance
use:
L > 100 A
Truck
53. Sag Vertical Curve: Example
A sag vertical curve is to be designed to join a –3% to
a +3% grade. Design speed is 40 mph. What is L?
Skipping steps: SSD = 313.67 feet S > L
Determine whether S<L or S>L
L = 2(313.67 ft) – (400 + 2.5 x 313.67) = 377.70 ft
[3 – (-3)]
313.67 < 377.70, so condition does not apply
Truck
54. Sag Vertical Curve: Example
A sag vertical curve is to be designed to join a –
3% to a +3% grade. Design speed is 40 mph.
What is L?
Skipping steps: SSD = 313.67 feet
L = 6 x (313.67)2
= 394.12 ft
400 + 3.5 x 313.67
313.67 < 394.12, so condition applies
Truck
55. Sag Vertical Curve: Example
A sag vertical curve is to be designed to join a –3% to a +3%
grade. Design speed is 40 mph. What is L?
Skipping steps: SSD = 313.67 feet
Testing for comfort:
L = AV2
= (6 x [40 mph]2
) = 206.5 feet
46.5 46.5
Testing for appearance:
L = 100A = (100 x 6) = 600 feet
Truck
56. Vertical Curve AASHTO
Controls (Sag)
• For curb drainage, want min. of
0.3 percent grade within 50’ of low
point = need Kmax
= 167 (US units)
• For appearance on high-type
roads, use min design speed of 50
mph (K = 100)
• As in crest, use min L = 3V
Truck
57. Other important
issues:
• Use lighting if need to use shorter
L than headlight requirements
• Sight distance at under crossings
Truck
58.
59. Example: A crest vertical curve joins a +3% and –4% grade.
Design speed is 75 mph. Length = 2184.0 ft. Station at
PVI is 345+ 60.00, elevation at PVI = 250 feet. Find
elevations and station for PVC (BVC) and PVT (EVC).
L/2 = 1092.0 ft
Station at PVC = [345 + 60.00] - [10 + 92.00] = 334 + 68.00
Vertical Diff PVI to PVC: -0.03 x (2184/2) = -32.76 feet
ElevationPVC = 250 – 32.76 = 217.24 feet
Station at PVT = [345 + 60.00] + [10 + 92.00] = 357 + 52.00
Vertical Diff PVI to PVT = 0.04 x (2184/2) = 43.68 feet
Elevation PVT = 250 – 43.68 = 206.32 feet
60. Example: A crest vertical curve joins a +3% and –
4% grade. Design speed is 75 mph. Length =
2184.0 ft. Station at PVI is 345+ 60.00, elevation
at PVI = 250 feet. Station at BVC (PVC) is 334 +
60.00, Elevation at BVC: 217.24 feet.
Calculate points along the vertical curve.
X = distance from BVC
Y = Ax2
200 L
Elevationtangent = elevation at BVC + distance x
grade
Elevationcurve = Elevationtangent - Y
61. Example: A crest vertical curve joins a +3%
and –4% grade. Design speed is 75 mph.
Length = 2184.0 ft. Station at PVI is 345+
60.00, elevation at PVI = 250 feet. Find
elevation on the curve at a point 400 feet from
BVC.
Y = A x 2
= - 7 x (400 ft)2
= - 2.56 feet
200L 200 (2814)
Elevation at tangent = 206.32 + (400 x 0.03) =
218.32
Elevation on curve = 218.32 – 2.56 feet =
226.68’
62. Calculating x from BVC, calculating tangent
elevation along +3% tangent
Y
63.
64. Calculating x from EVC, calculating tangent
elevation along +4% tangent
Y