A speed cushion is a vertical-deflection traffic-calming device split into 2 to 4 segments with wheel-track gaps sized to fire-apparatus axle width, so fire engines and ambulances can straddle the device while passenger cars hit the segments and slow to 18 to 22 mph. The Federal Highway Administration's Traffic Calming ePrimer Module 3.4 defines the device, and the Institute of Transportation Engineers (ITE) Traffic Calming Manual, Chapter 3, sets the dimensional standards. Cushions are the preferred traffic-calming tool on fire-access streets.
What Is a Speed Cushion?
A speed cushion consists of:
- 2 to 4 raised pavement segments, typically 6 feet long by 6 feet wide by 3 to 3.5 inches tall each
- Wheel-track gaps between the segments, sized to local fire-apparatus rear-axle width (commonly 1.6 to 1.85 meters / 63 to 73 inches, sometimes 80+ inches for North American Type 1 engines)
- Total cushion footprint typically 13 to 18 feet across the travel lane
The defining feature is the wheel-track gap. A vertical-deflection device without wheel-track gaps is a speed bump (under 3 feet long) or a speed hump (12 to 14 feet long), not a speed cushion.
Why Were Speed Cushions Invented?
Speed cushions emerged in northern Europe in the 1990s as a response to fire department objections against speed humps on residential streets. Fire departments documented unacceptable response delays caused by traditional vertical-deflection devices: speed humps slowed fire engines to 8 to 12 mph, adding 5 to 9 seconds of delay per device. On a residential street with three humps, total response delay reached 15 to 27 seconds; on streets with five or more devices the delays reached a minute or more.
The cushion design solves the conflict. By splitting the device into segments with gaps sized to fire-apparatus axle width, designers preserved the speed-reduction effect on passenger cars while letting fire trucks straddle the device with one tire path through each gap. Fire-truck delay drops from 5 to 9 seconds to under 2 seconds per cushion.
The Federal Highway Administration imported the device into US practice in the early 2000s and codified it in the Traffic Calming ePrimer.
What Is the Purpose of a Speed Cushion?
Three jobs:
- Slow passenger cars to 18 to 22 mph at the cushion (85th-percentile speed)
- Preserve emergency-vehicle access by letting fire trucks and ambulances straddle the device
- Allow transit buses to maintain near-normal operating speeds because most North American bus axle widths match fire-apparatus widths
The combination of these three jobs is what makes cushions different from any other vertical-deflection device.
Where Are Speed Cushions Used?
| Use case | Why cushions fit |
|---|---|
| Residential fire-access streets | Preserves apparatus access while calming traffic |
| Hospital service roads | Ambulance and patient-transport vehicle access |
| School zones with bus routes | Bus delay stays under 3 seconds per cushion |
| Neighborhood greenways on EMS corridors | Combines pedestrian/bike priority with emergency response |
| University campus loops | Many campuses have internal fire-access requirements |
| Hotel and resort access roads | Where fire access overlaps with guest traffic calming |
- Parking lots (use rubber speed bumps instead, no fire-access conflict)
- Highway interchanges (speeds too high for any vertical-deflection device)
- Streets with no fire-access constraint (speed humps are cheaper and produce more speed reduction)
For dimensional detail see speed cushion dimensions, and for engineering background see how do speed cushions work.
How Do Speed Cushions Compare with Speed Bumps and Humps?
| Device | Length (travel) | Use case | Fire-truck delay |
|---|---|---|---|
| Speed bump | 1 to 3 feet | Parking lots only | 6 to 10 seconds (severe) |
| Speed hump | 12 to 14 feet | Residential streets without fire-access concern | 5 to 9 seconds |
| Speed cushion | 6 to 7 feet per segment with gaps | Fire-access, EMS, transit corridors | Under 2 seconds |
| Speed table | 22 feet | Streets with marked crosswalks or transit routes | 2 to 4 seconds |
What Materials Are Speed Cushions Made From?
| Material | Lifespan | Best fit |
|---|---|---|
| Modular rubber | 7 to 10 years | Most residential and fire-access installs |
| Asphalt cast-in-place | 12 to 18 years | Long-term residential greenways |
| Polyurethane / plastic | 4 to 7 years | Pilot programs, short-term installs |
| Concrete | 25 to 35 years | Industrial and hospital service roads |
Are Speed Cushions Approved in Oregon?
Yes. All Tier 1 Oregon cities (Portland, Salem, Eugene, Springfield) have included speed cushions in their residential traffic-calming program menus. Tier 2 cities (Bend, Beaverton, Hillsboro, Gresham, Corvallis, Albany, Medford) have approved cushions on a case-by-case basis. Local fire departments review wheel-track gap dimensions before installation.
The Portland Bureau of Transportation Neighborhood Greenways and Traffic Calming program is the most prolific Oregon user of speed cushions; PBOT has installed cushions on dozens of greenway corridors that overlap with fire-access routes. Eugene Public Works pairs cushion installs with Vision Zero priority corridors on streets with bus and EMS service.
From Our Crew
On a Tigard fire-access greenway in late 2024, Cojo installed a set of three modular rubber speed cushions for Tualatin Valley Fire & Rescue. The wheel-track gap was specified at 1.85 meters from the department's tower-truck axle measurement. Post-install drive-through delay measured by the department was 1.8 seconds per cushion at code-3 response. The same corridor with traditional speed humps would have produced 18 to 27 seconds of delay across three devices. The cushion configuration was the only design that preserved response time while still calming passenger-car speeds.
What Reference Documents Define Speed Cushions?
- ITE Traffic Calming Manual, Chapter 3 (Speed Cushions section)
- FHWA Traffic Calming ePrimer, Module 3.4
- NFPA 1141, Chapter 5 (fire-protection infrastructure for residential development)
- IFC Section 503 (fire-apparatus access roads)
Always verify current requirements with your local jurisdiction. This article reflects May 2026 published guidance.
Need a Speed Cushion for Your Street?
Cojo provides speed cushion installation across the Oregon I-5 corridor. We coordinate fire-marshal review and dimensional sign-off, traffic-calming application packets, and installation in one scope. See the speed cushions guide for the broader product context, speed cushion dimensions for spec detail, and how do speed cushions work for engineering background. For Portland-area installs see Speed Cushion Installation Portland or pair the install with our asphalt maintenance services. Get a custom quote.