The decision rule is simple: posted speed and ownership. Public residential streets with 20 to 25 mph posted speeds get speed humps. Private parking lots and drive-aisles with 5 to 10 mph design speeds get speed bumps. A 12-foot parabolic hump at 5 mph is overkill; a 2-foot bump at 25 mph causes vehicle damage. Match the device to the street.
Decision tree
| Question | If yes | If no |
|---|---|---|
| Is this a public street with 20+ mph posted speed? | Speed hump | Continue |
| Is this a private street or HOA road with 25 mph design speed? | Speed hump | Continue |
| Is this a parking lot drive-aisle (5 to 10 mph)? | Speed bump | Continue |
| Is this a private driveway with mixed pedestrian use? | Speed bump | Reassess |
Why does posted speed matter?
Speed humps are calibrated for the 15 to 20 mph speed range. A 12-foot parabolic hump at 5 mph barely registers on the suspension; drivers do not slow because the device does not deliver enough physical feedback at low speed. A speed bump (1 to 3 ft long) at 25 mph delivers a sharp jolt that risks oil-pan, exhaust-system, and suspension damage and can lift wheels off the pavement at posted speed.
The Institute of Transportation Engineers (ITE) Traffic Calming Manual Chapter 3 specifies humps for streets with 25 mph posted speeds and bumps for parking lots and private driveways with much lower design speeds. The Federal Highway Administration's Traffic Calming ePrimer notes that "speed humps are designed to allow vehicles to pass over them comfortably at the desired speed of 15 to 25 mph" while bumps are "intended to be encountered at less than 5 mph" (FHWA ePrimer).
Why does ownership matter?
Public streets typically require a city traffic-calming program review. The hump (not the bump) is the device most cities will install on public roads. Portland's Bureau of Transportation, Salem Public Works, and Eugene Public Works all spec humps for public-street traffic calming and explicitly do not install bumps on public roads.
Private property is the opposite. HOA boards, retail centers, and apartment complexes install bumps because the design speed in a parking lot or shared drive aisle is 5 to 10 mph. Bumps are the right device at that speed. Installing a hump in a 100-stall parking lot misallocates pavement and raises driver complaints because the device is calibrated for traffic the lot does not carry.
When is the call not obvious?
Three edge cases force a closer look:
Long private driveways
A 600-foot driveway from a country road to a rural home may carry traffic at 20 to 25 mph if the driver is comfortable with the surface. In that scenario, a speed hump is the better device. A speed bump on the same driveway would damage vehicles at the natural travel speed.
HOA streets in planned communities
Oregon ORS Chapter 94 governs HOA authority over streets in planned communities. Some HOA streets function as residential collectors (25 mph) with through-traffic; these get humps. Other HOA streets are essentially extended driveways with cul-de-sac patterns (10 mph); these can get bumps. The litmus test is whether the street has stop signs at the entrance to the property; if so, drivers reset to a higher cruise speed past the entrance and the hump is the right device.
Shared drive aisles in dense apartment complexes
The drive aisle between buildings in a 200-unit complex sometimes carries traffic at 15 to 18 mph, faster than a typical parking lot but slower than a residential street. Both bumps and humps work; the cost-per-unit difference favors bumps when 4+ devices are needed across the property. In a 2025 install for a Beaverton apartment complex (180 units, 4 bumps across the property), our crew confirmed device choice with a 24-hour spot-speed survey before install.
How does cost factor into the decision?
Industry Baseline Range
| Device | Installed Cost | Lifespan | Annualized Cost |
|---|---|---|---|
| Speed bump (rubber, parking-lot) | $200 to $1,000 | 5 to 10 years | $40 to $200/year |
| Speed bump (asphalt, parking-lot) | $300 to $1,500 | 7 to 12 years | $40 to $215/year |
| Speed hump (asphalt, residential) | $1,500 to $5,000 | 15 to 25 years | $80 to $330/year |
Current market reality
Annualized cost is a closer comparison than install cost because humps last 2 to 3 times as long as bumps. On lifecycle math, the hump is more expensive but not by the 3 to 5 times that install pricing implies. On the ITE-correct application (humps on streets, bumps in lots), the cost question rarely flips the device choice; if the street demands a hump for safety, the lifecycle math supports it.
What devices are alternatives?
Two devices to consider when bumps and humps both feel wrong:
- Speed cushions (split-hump with wheel-track gaps) for streets where fire-truck access matters. See speed hump vs speed cushion.
- Speed tables (22-ft flat-top) for streets with bus or fire-priority traffic. See speed hump vs speed table.
For parking lots looking for an alternative to bumps (e.g. retail centers wanting a softer slowing approach), wheel-stops, painted speed lines, or geometric calming (curb extensions, chicanes) sometimes solve the problem at lower cost.
Frequently asked questions
Can I install a speed hump in my parking lot? You can, but you probably should not. Humps are calibrated for 15 to 25 mph speeds. Most parking lots run at 5 to 10 mph; a hump at that speed delivers little slowing benefit and consumes pavement. Use a speed bump.
Can I install a speed bump on a public street? Almost no Oregon city will allow it. Speed bumps on public roads at 25 mph cause vehicle damage and emergency-vehicle problems. Public-street traffic calming uses humps, cushions, or tables.
What if my driveway is private but long? Long private driveways at 20+ mph design speeds get humps. Short driveways at 5 mph design speeds get bumps. The natural cruise speed is the test.
Does ITE actually have a rule on this? ITE's Traffic Calming Manual Chapter 3 distinguishes humps and bumps by application. The text reads as guidance, not a formal rule, but every U.S. traffic-engineering practice follows it.
Is a speed bump cheaper than a speed hump? Yes, by 3 to 5 times on install cost. Annualized over the device lifespan, the gap shrinks to roughly 2 times. The right device for the street still wins; cost rarely flips the call.
Get the Right Device
Cojo specifies and installs the right traffic-calming device for each site, from rubber speed bumps in parking lots to asphalt humps on residential streets. Contact Cojo for a site assessment, or learn more about our asphalt paving services.