Traffic and Highway Engineering
5th Edition
ISBN: 9781305156241
Author: Garber, Nicholas J.
Publisher: Cengage Learning
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Question
Chapter 5, Problem 20P
To determine
The crash modification factor for a horizontal curve on a two-lane rural highway.
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A curve of radius 76 m and e = 0.08 is located at a section of an existing rural highway, which restricts the safe speed at this section of the highway to 50% of the design speed. This drastic reduction of safe speed resulted in a high crash rate at this section. To reduce the crash rate, a new alignment is to be designed with a horizontal curve. Determine the minimum radius of this curve if the safe speed should be increased to the design speed of the highway. Assume fs = 0.17 for the existing curve. The new curve is to be designed with the same superelevation
A curve of radius 250 ft and e 0.08 is located at a section of an existing rural highway, which restricts the safe speed at this section of the highway to 50% of the design speed. This drastic reduction of safe speed resulted in a high crash rate at this section. To reduce the crash rate, a new alignment is to be designed with a horizontal curve. Determine the minimum radius of this curve if the safe speed should be increased to the design speed of the highway. Assume fs= 0.17 for the existing curve, and the new curve is to be designed with e = 0.08
A vertical curve was designed in 2005 for SSD requirements at a design speed of 120 km/h to
connect grades G1=+2% and G2=-3%. The curve is to be redesigned for the same design speed
in 2025. Vehicle braking technology has advanced such that the vehicle deceleration rate has
increased by 40% relative to the value used in the original design. However, due to the higher
percentage of older people in the driving population, design reaction times have increased by
20%. Compute the difference in design curve lengths for the 2005 and 2025 designs based on
Australian guidelines.
Chapter 5 Solutions
Traffic and Highway Engineering
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- Problem 5 An existing horizontal curve on a highway has a radius of 465 ft, which restricts the posted speed limit to only 61.5% of the design speed on this section of the highway. If the curve is to be improved, so that its posted speed will be the design speed of the highway, determine the minimum radius of the new curve. Assume that the rate of superelevation is 0.08 for both the existing curve and the new curve to be designed and f,=0.16 for 40 mph, 0.14 for 50 mph, 0.12 for 60 mph, and 0.10 for 70 mph.arrow_forwardA horizontal curve is to be designed for a section of a highway having a design speed of 60 mi/h. (a) If the physical conditions restrict the radius of the curve to 500 ft, what value is required for the superelevation at this curve?(b) Is this a good design?arrow_forward3. A curve of radius 250 ft and e= 0.08 is located at a section of an existing rural highway, which restricts the safe speed at this section of the highway to 50% of the design speed. This drastic reduction of safe speed resulted in a high crash rate at this section. To reduce the crash rate, a new alignment is to be designed with a horizontal curve. Determine the minimum radius of this curve if the safe speed should be increased to the design speed of the highway. Assume fs=0.17 for the existing curve, and the new curve is to be designed with e = 08.?arrow_forward
- A highway reconstruction project is being undertaken to reduce crash rates. The reconstruction involves a major realignment of the highway such that a design speed of 100km/h attained. At one point on the highway, a 245m equal-tangent crest vertical curve exists. Measurements show that at 0+107.3 stations from the PVC, the vertical curve offset is 1 meter. Assess the adequacy of this existing curve in light of the reconstruction design speed of 100km/h and if the existing curve is inadequate, compute a satisifactory curve length.arrow_forwardWhat is the minimum length of vertical curve that must be provided to connect a 5% grade with a 2% grade on a highway with a design speed of 60 mi/h? Driver reaction time is the AASHTO standard of 2.5 s for simple high- way stopping reactions.arrow_forwardWhat is the appropriate super elevation rate for a curve with a 1,200-ft radius on highway with a design speed of 60 mi/h? The maximum design super elevation is 6% for this highway.arrow_forward
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- A section of highway has vertical and horizontal curves with the same design speed. A vertical sag curve on this highway connects a +1% and a +3% grade and is 420 ft long. If a horizontal curve on this highway is on a two-lane section with 12ft lanes, has a central angle of 37 degrees, and has a superelevation of 6%, what is the length of the horizontal curve?arrow_forwardThe radius of a horizontal curve on an existing highway was field- measured to be 275 m. The on this two-lane pavement highway is 6.8 m wide, and the elevation difference between the inside edge and outside edge of the curve is 0.544 m. The posted speed limit on the road is 100 km/h. Determine the minimum radius of curvature to permit safe operation at the speed limit. 1arrow_forwardA new transportation engineer is charged with the design of a horizontal curve a certain highway. His final design calls for a curve with a radius of 520 meters. Assume that the design speed for the highway is 110 km/h. Is the design curve acceptable? Consider super elevation of 8% and a maximum side friction factor of 0.1.arrow_forward
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