Speed Cushions
What Are Speed Cushions? Complete 2026 Guide
Cojo
May 7, 2026
7 min read
A speed cushion is a traffic-calming device built like a speed hump but split into 2 or 3 segments, with wheel-track gaps wide enough for fire-truck axles to straddle. Cars hit the cushion full-on and slow to 15 to 20 mph. Fire trucks and ambulances ride through the gaps and hold 20 to 25 mph. The whole reason cushions exist: a speed hump on a fire-access route adds enough response-time delay that on a serious call it's the difference between a save and a loss. Below: the engineering, the use cases, and the design specs our crews build to.
A speed cushion is a series of 2 or 3 raised segments, each typically 6 feet by 6 feet by 3 inches tall, separated by wheel-track gaps approximately 6 feet wide. The total cushion device spans the full lane width. A passenger car cannot avoid hitting at least one segment with each wheel-track and is slowed by the contact. A fire truck with a wider axle straddles the segments and rides through the gaps without the vertical pulse a hump would deliver.
Single-purpose: emergency-vehicle compatibility. The Federal Highway Administration's Traffic Calming ePrimer documents fire-truck response-time delays of 5 to 10 seconds per speed hump. On a fire-response route with 4 or 5 humps, the cumulative delay can exceed 30 seconds. Speed cushions deliver most of the calming benefit (6 to 8 mph reduction in 85th-percentile passenger-car speed) with negligible fire-truck delay. The NFPA 1141 fire-access standard treats cushions as the device of choice on fire-response calming routes.
| Variable | Speed hump | Speed cushion |
|---|---|---|
| Footprint | Full lane width, 12 to 14 ft long | Full lane width, 6 to 7 ft long |
| Construction | Single continuous raised section | 2 or 3 segments with wheel-track gaps |
| Passenger-car speed reduction | 7 to 9 mph | 6 to 8 mph |
| Fire-truck delay | 5 to 10 seconds per hump | 1 to 3 seconds per cushion |
| Bus impact | Moderate (lifts gurneys, jolts standees) | Lower (most buses straddle one gap) |
| Ambulance impact | High | Low |
| Material | Mostly asphalt | Asphalt or modular rubber |
| Cost per unit | $2,000 to $5,000+ | $2,500 to $8,000+ |
Five primary use cases.
The original use case. Any road that serves as a fire-response corridor and also needs calming -- residential greenways with fire-truck access, hospital-campus drives, school-zone fire lanes -- is a candidate. The Portland Fire Code and the Tualatin Valley Fire and Rescue access standards both recognize cushions as the preferred calming device on response routes.
A speed table is gentler for buses than a cushion, but cushions work where buses are infrequent and the corridor needs more calming than a table provides. Most TriMet, LTD, and Lane Transit routes can ride cushions without service issues.
Streets that serve a mix of passenger cars, residential traffic, and delivery vehicles benefit from cushions because the wheel-track gaps reduce delivery-vehicle suspension wear and complaint volume.
A series of 3 or 4 cushions spaced 250 to 350 feet apart can calm a corridor without imposing the cumulative fire-truck delay of an equivalent hump series.
Internal calming on campuses where ambulance flow is constant. A cushion slows visiting cars to 15 mph without delaying ambulance arrivals at the ED entrance.
| Variable | Recommended | Source |
|---|---|---|
| Segment length (travel direction) | 6 to 7 ft | ITE Traffic Calming Manual |
| Segment width (across road) | 5 to 6 ft | ITE / FHWA |
| Segment height | 3 to 3.5 in | ITE / FHWA |
| Wheel-track gap width | 5.5 to 6 ft | NFPA / fire-marshal |
| Number of segments per cushion | 2 or 3 (lane width dependent) | Local jurisdiction |
| Profile | Parabolic | ITE |
| Material | Asphalt or modular rubber | Property choice |
| Marking | Yellow chevrons on each segment | MUTCD W17-1 |
Permanent installation. Crew forms each segment with a paving template, places hot-mix asphalt, compacts to grade, and shapes the parabolic profile. Lifespan 7 to 10 years on parking lots, 5 to 7 years on residential streets. Most common in Cojo's Portland-metro project work.
Bolt-on units sized to the segment dimensions. Faster install (4 to 6 hours per cushion vs 1 to 2 days for asphalt), removable, and material-cost-only when the design needs adjustment. Lifespan 5 to 8 years before bolts and rubber sections fatigue. Common on private property where future flexibility matters.
Niche use. Longer lifespan than asphalt (12 to 20 years) but harder to modify. Used on high-volume HOA entry roads where lifespan is the primary variable.
Per MUTCD Part 2C and the FHWA Traffic Calming ePrimer:
Some jurisdictions use a custom CUSHION sign or marking instead of HUMP -- check the local agency's signage spec sheet.
Effectiveness data from the FHWA CMF Clearinghouse and the ITE Traffic Calming Manual:
Cushions trade about 1 mph of passenger-car speed reduction for 5 to 7 seconds of fire-truck delay savings per device. On any route where fire-truck delay matters, the trade is worth it.
In late 2025 Cojo installed a series of 3 asphalt speed cushions on a fire-access road in Tigard after the Tualatin Valley Fire and Rescue district flagged a proposed hump install as response-route incompatible. The corridor needed both calming (resident-petition driven) and uncompromised fire access. Pre-install 85th-percentile speeds were 28 mph; 60-day post-install measured 21 mph. TVF&R measured fire-truck delay through the cushion series at 5 seconds total (vs 25 to 30 seconds for an equivalent hump series).
If you are a fire marshal, traffic engineer, HOA board member, or property manager evaluating cushions vs humps, Cojo can provide a free site review. See the speed humps guide for the device-comparison context, speed cushion vs speed table for the table comparison, best speed cushions for product picks, speed cushion installation in Portland for a local example, or asphalt maintenance services for the install scope and pricing.
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