A speed hump (also called a road hump, or undulation,and speed ramp in Ireland) is a rounded traffic calming device used to reduce vehicle speed and volume on residential streets. Humps are placed across the road to slow traffic and are often installed in a series of several humps in order to prevent cars from speeding before and after the hump. Common speed hump shapes are parabolic, circular, and sinusoidal.
Generally, speed humps are 12 to 14 feet (3.7 to 4.25 m) in length and span the width of the road. The height of humps ranges from 3 to 4 inches (7.5 to 10 cm). The length and height of the speed humps determine the speed at which traffic will travel over the devices. Shorter lengths and greater heights slow cars most drastically. When placed in a series 350–550 feet (100–170 m) apart, humps will reduce 85 percentile speeds by 8–10 mph (13–15 km/h).
A warning sign notifies motorists before humps. Humps generally have pavement markings to enhance visibility and a taper edge near the curb to allow a gap for drainage.
Speed humps are used in locations where very low speeds are desired and reasonable. Speed humps are typically placed on residential roads and are not used on major roads, bus routes, or primary emergency response routes. Placement is generally mid-block between intersections.