Traffic And Highway Engineering
5th Edition
ISBN: 9781133605157
Author: Garber, Nicholas J., Hoel, Lester A.
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_forwardWrite your answers and solutions.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_forward
- 3. 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_forwardWrite your step by step solutionsarrow_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_forward
- What 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_forwardA large grain elevator is located 40 ft from the centerline of a two- lane highway, which has 12-ft lanes. The elevator is situated on the inside of a l12° horizontal curve. a) Assuming that the elevator is the only sight restriction on the curve, what is the minimum sight distance along the curve? b) What should be the maximum speed recommended for this curve? c) If the designer wants to have the design speed of 10 mph higher that the recommended speed, what is the distance required for the movement of the elevator?arrow_forwardA highway reconstruction project is being undertaken to reduce accident rates. The reconstruction involves a major realignment of the highway such that a 50 mph design speed is attained. At one point on the highway, an 800 ft equal tangent crest vertical curve exists. Measurements show that at 3-52 stations from the PVC, the vertical curve offset is 3 ft. Assess the adequacy of this existing curve in light of the reconstruction design speed of 60 mph and, if the existing curve is inadequate, compute an adequate curve length.arrow_forward
- A 300 m radius highway curve is to be superelevated so that skidding will not be impending at speeds below km 100 . If the minimum u is assumed to be 0.2, what superelevation in mm is required for a 8 m roadway? hr What will be the most comfortable speed for the passengers on this curve if it has the superelevation found above?arrow_forwardFind the length of transition curve and extra width of pavement required on a horizontal curve of radius 300 m of a two lane highway passing through rolling terrain for a design speed of 80 kmph. (Assume all other data as per IRC recommendations)arrow_forwardA 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_forward
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