Speed tables are midblock traffic calming devices that raise the entire wheelbase of a vehicle to reduce its traffic speed. Speed tables are longer than speed humps and flat-topped, with a height of 3–3.5 inches and a length of 22 feet. Vehicle operating speeds for streets with speed tables range from 25–45 mph, depending on the spacing.1 Speed tables may be used on collector streets and/or transit and emergency response routes. Where applied, speed tables may be designed as raised midblock crossings, often in conjunction with curb extensions.
Critical
Speed tables shall be accompanied by a sign warning drivers (MUTCD W17-1).
Recommended
Speed tables 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.
Speed tables should not be applied on streets wider than 50 feet. On 2-way streets, speed tables may be applied in both directions.
Where a speed table coincides with a crossing or crosswalk, it should be designed as a raised crosswalk.
Locate vertical speed control elements where there is sufficient visibility and available lighting.
Optional
Speed tables are often designed using unit pavers or other distinctive materials. Distinctive materials may require additional maintenance responsibilities but help to highlight and define the speed table for both bicyclists and pedestrians.
This speed table has been designed as a raised crossing.
- Portland installs 22-foot speed humps on streets with 85th-percencile speeds of 35–45 mph.
“Speed Bumps,” Bureau of Traffic Management Traffic Manual (Portland: Portland Bureau of Transportation). ↩︎