# Fundamentals of Transportation/Horizontal Curves/Homework

## Homework

1. Why might maximum superelevation be higher in South Texas than in Northern Minnesota?

2. Which conic section forms the basis of horizontal curves?

3. When a vehicle is traveling around a horizontal curve, it is subject to two forces. What are these forces, and how do they operate on the vehicle (draw a clear diagram illustrating the forces).

4. An existing horizontal curve has a radius of 100 meters, which restricts the maximum speed on this section of road. Highway officials want a maximum design speed of 150 km/hr.

Assume the coefficient of side friction is 0.15 and rate of superelevation on both the original and rebuilt sections is 0.06.

Compute the existing speed and find the new radius of curvature.

5. A flat horizontal curve on a 2-lane highway is designed with a 609.600 m radius, the curve has a tangent length of 121.920 m and the PI is at station 3+139.440

Design Speed (km/h) Brake reaction distance (m) Braking distance on level (m) Calculated Stopping Sight Distance (m) Design Stopping Sight Distance (m)
80 55.2 73.4 129.0 130
90 62.6 92.9 155.5 160
100 69.5 114.7 184.2 185
110 76.5 138.8 215.3 220

Source: AASHTO: A Policy on Geometric Design of Highways and Streets

The road has 3.6 m lanes and a 96 km/h design speed.

a. Determine the stationing of the PT. Draw your solution. b. Determine the distance that must be cleared from the inside edge of the inside lane to provide sufficient stopping sight distance. Draw your solution.

6. A horizontal curve is designed with a 600 m radius. The curve has a tangent of 125 m and the PI is at metric station 10+000 (10 kilometers and 0 meters). Determine the stationing of the PT. Draw a diagram showing your answer.