Horizontal Curves

1. You are asked to design a horizontal curve for a two-lane road. The road has 12-ft lanes. Due to expensive excavation, it is determined that a maximum of 34 ft can be cleared from the road’s centerline toward the inside lane to provide for stopping sight distance. Also, local guidelines dictate a maximum superelevation of 0.08 ft/ft. What is the highest possible design speed for this curve?

2. A horizontal curve on a two-lane highway (10- ft lanes) is designed for 50 mi/h with a 6% superelevation. The central angle of the curve is 35 degrees and the PI is at station 482 + 72. What is the station of the PT and how many feet have to be cleared from the lane’s shoulder edge to provide adequate stopping sight distance?

3. A horizontal curve on a single-lane highway has its PC at station 123 + 70 and its PI at station 130 + 90. The curve has a superelevation of 0.06 ft/ft and is designed for 70 mi/h. What is the station of the PT?

4. A horizontal curve is being designed through mountainous terrain for a four-lane road with lanes that are 10 ft wide. The central angle ( ) is known to be 40 degrees, the tangent distance is 520 ft, and the stationing of the tangent intersection (PI) is 2600 + 00. Under specified conditions and vehicle speed, the roadway surface is determined to have a coefficient of side friction of 0.08, and the curve’s superelevation is 0.09 ft/ft. What is the stationing of the PC and PT and what is the safe vehicle speed?

5. A new interstate highway is being built with a design speed of 70 mi/h. For one of the horizontal curves, the radius (measured to the innermost vehicle path) is tentatively planned as 2500 ft. What rate of superelevation is required for this curve?

6. On a roadway with two 12-ft lanes, a horizontal curve is designed for 35 mi/h with a 4% superelevation. It is known that = 2 s. The PI of the curve is at station 30 + 00. What is the station of the PT of the curve?

7. A developer is having a single-lane raceway constructed with a 200-mi/h design speed. A curve on

the raceway has a radius of 4500 ft, a central angle of 30 degrees, and PI stationing at 1125 + 10. If the design coefficient of side friction is 0.20, determine the superelevation required at the design speed (do not ignore the normal component of the centripetal force). Also, compute the degree of curve, length of curve, and stationing of the PC and PT.