Speed cushions are either speed humps or speed tables that include wheel cutouts to allow large vehicles to pass unaffected, while reducing passenger car speeds. They can be offset to allow unimpeded passage by emergency vehicles and are typically used on key emergency response routes. Speed cushions extend across one direction of travel from the centerline, with a longitudinal gap provided to allow wide wheelbase vehicles to avoid going over the hump.
Critical
When vertical speed control is implemented on major emergency access routes, use speed cushions designed to accommodate the wheelbase of the emergency vehicle.1
Vertical speed control should be accompanied by a sign warning drivers (MUTCD W17-1).
Recommended
Vertical speed control elements should be designed to the following criteria:
- Slopes should not exceed 1:10 or be less steep than 1:25.
- Side slopes on tapers should be no greater than 1:6.
- The vertical lip should be no more than a quarter-inch high.
Locate speed cushions where there is sufficient visibility and available lighting.
Optional
Bus routes may have speed cushions installed on certain routes. Work with local transit providers and bus companies to ensure that drivers are aware of traffic calming devices and can effectively use wheel cutouts provided.
area.
- In one case study in King County, WA, the fire department found cushions minimized response time increases as compared to other traffic calming devices.
Kevin Chang and Matthew Nolan, An Evaluation of Speed Cushions on Neighborhood Streets: Balancing Emergency Vehicle Mobility With Traffic Calming Needs (Washington, D.C.: Institute for Transportation Engineers, 2006). ↩︎