Speed Cushions
Speed Cushion Dimensions: Standard Size & Wheel-Gap Spec (2026)
Cojo
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A standard speed cushion segment is 6 feet long by 6 feet wide by 3 inches tall, installed in groups of 2 or 3 segments per cushion to leave 1.85-meter (72 to 73 inch) wheel-track gaps that match fire-apparatus rear axle width. The Federal Highway Administration's Traffic Calming ePrimer Module 3.4 and the Institute of Transportation Engineers (ITE) Traffic Calming Manual, Chapter 3, document these dimensions. The wheel-track gap is the dimension that distinguishes a speed cushion from a speed bump or speed hump.
| Dimension | Standard value | Notes |
|---|---|---|
| Cushion segment length (travel direction) | 6 to 7 feet | Equivalent to a long speed bump or short speed hump |
| Cushion segment width (across travel) | 6 feet | Per segment |
| Cushion segment height | 3 to 3.5 inches | Same as a speed hump |
| Wheel-track gap | 1.6 to 1.85 meters (63 to 73 in) | Sized to local fire-apparatus axle width |
| Total cushion footprint width | 13 to 18 feet across travel lane | Depends on lane count and segment configuration |
| Number of segments per cushion | 2 to 4 | Most common is 3 (2 outside, 1 center) |
A speed cushion's purpose is to slow passenger cars while letting fire engines and ambulances pass at near-normal speed. Passenger cars have rear-axle track widths in the 50 to 65 inch range, narrower than fire apparatus. Fire engines and aerial ladder trucks typically have rear-axle outside-to-outside dimensions of 78 to 84 inches. A cushion with wheel-track gaps sized to the fire-apparatus width lets the truck straddle the cushion (with one tire path on each side of the device), while the narrower-track car hits the cushion segments full-on.
The USFA Emergency Vehicle Safety Initiative publishes ladder-truck axle data many municipal fire departments use as their wheel-track gap reference. NFPA 1141 chapter 5 on fire-protection infrastructure for residential development provides the framework municipalities use to evaluate whether a proposed cushion preserves required fire-apparatus access. Cushions installed without fire-marshal sign-off on the wheel-track gap routinely fail department review and require re-installation.
| Lane scenario | Typical configuration | Wheel-track gap count |
|---|---|---|
| One-lane residential street | 2 outside segments, 1 wheel-track gap | 1 |
| Two-lane residential street | 3 segments per direction, 2 outside-lane gaps | 2 per direction |
| Two-lane bidirectional with center turn lane | 3 segments per direction, gaps aligned across centerline | 2 per direction |
| Four-lane collector | 4 segments per direction, 2 outside-lane gaps + 1 inside-lane gap | 3 per direction |
The 3 to 3.5 inch standard height is the same as a speed hump and the same as a typical 3-inch speed bump. ITE Traffic Calming Manual Chapter 3 documents this as the height that produces meaningful 85th-percentile speed reduction (typically to 18 to 22 mph) while remaining within passenger-car suspension tolerance.
Heights below 2.75 inches do not produce reliable speed reduction. Heights above 3.5 inches risk passenger-car damage and exceed published ITE recommendations. Always verify current local jurisdiction guidance before specifying a non-standard height.
The following are reference values only. Always confirm with the local fire department before specifying.
| Apparatus class | Typical rear-axle outside-to-outside | Recommended gap |
|---|---|---|
| Type 1 engine (typical) | 80 to 84 inches | 84 inches (2.13 m) |
| Type 1 engine (urban) | 78 to 80 inches | 80 inches (2.03 m) |
| Aerial ladder truck (typical) | 78 to 82 inches | 82 inches (2.08 m) |
| Quint apparatus (combo engine + ladder) | 80 to 84 inches | 84 inches (2.13 m) |
| Heavy rescue | 78 to 82 inches | 82 inches (2.08 m) |
| Tower truck (Tigard / Tualatin Valley F&R example) | 72 to 73 inches | 73 inches (1.85 m) |
A typical 3-segment cushion on a 24-foot residential street looks like:
This places one wheel-track gap in each direction's outside lane (where fire trucks travel) while ensuring no through-path exists for a passenger car. Adjusting segment widths fits different lane counts and curb-to-curb dimensions.
On a Tigard fire-access greenway in late 2024, Cojo installed three modular rubber speed cushions configured to a 1.85-meter wheel-track gap. Tualatin Valley Fire & Rescue specified the gap from their tower-truck axle measurement; the field crew verified the gap on each cushion before drilling anchor holes. We documented the as-built gap measurements on a layout drawing and submitted the drawing to the city engineering department after install, which is standard close-out practice for any fire-access traffic-calming work.
| Device | Length (travel) | Width (across) | Height | Wheel-track gaps |
|---|---|---|---|---|
| Speed bump | 1 to 3 feet | Full lane | 3 to 4 inches | None |
| Speed hump | 12 to 14 feet | Full lane | 3 to 4 inches | None |
| Speed cushion | 6 to 7 feet (per segment) | 6-foot segments + gaps | 3 to 3.5 inches | Yes, sized to fire apparatus |
| Speed table | 22 feet (10-ft flat top + 6-ft ramps) | Full lane | 3 to 4 inches | None (use full width) |
Always verify current requirements with your local jurisdiction. This article reflects May 2026 published guidance.
Cojo coordinates fire-marshal review and dimensional sign-off on every cushion install across the Oregon I-5 corridor. We document as-built wheel-track gaps on the project drawing and submit close-out documentation to the city engineering department. For the install procedure see how to install a speed cushion, and for the broader product context see the speed cushions guide. For Salem-area installs see Speed Cushion Installation Salem or pair installation with our asphalt maintenance services. Get a custom quote.
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