Transportation Engineering

Stopping Sight Distance

The distance a driver needs to see ahead to perceive a hazard, react and brake to a stop.

Stopping sight distance is the distance travelled during the perception-reaction time, 1.47Vt with t = 2.5 s, plus the braking distance V²/[30(a/32.2 ± G)] with a = 11.2 ft/s². At 60 mph on the level it is about 570 ft. A downgrade lengthens it and an upgrade shortens it.

It governs the minimum length of crest vertical curves, where the road itself blocks the view, and of sag curves at night, where headlights limit it. On horizontal curves it sets how far back cut slopes and buildings must stay from the inside lane.

How much of the FE Civil exam is Transportation Engineering?