Traffic calming

Traffic calming is a set of street design strategies that slow down cars and make roads safer for people walking and cycling. There are many shapes and forms of traffic calming devices, and the details matter—some designs are terrible for everyone, while others work remarkably well.

Not Just Bikes has a good visual overview of what works and what doesn’t:

Bumps, humps, and cushions#

Not all raised devices are created equal—the profile, width, and placement of each type make a big difference for both safety and comfort.

• Q+A: Bumps, Humps, Cushions, Tables — What’s the Best Way to Slow Down Traffic?
• Federal highway adminstration: Effects of Traffic Calming Measures on Non-Personal Passenger Vehicles

Fire trucks#

A common objection to traffic calming is that it delays or damages fire trucks. The evidence seems clear: well-designed devices like speed cushions cause little to no delay or damage.

• Federal highway adminstration: Effects of Traffic Calming Measures on Non-Personal Passenger Vehicles

Damage to fire vehicles is another concern of fire departments. Opinions by some critics in the 1990s and early 2000s were that traffic calming measures caused damage to fire vehicles. ii For example, the stress of traveling over speed humps could lead to increased repairs and shorter vehicle life. However, the early studies found no data to substantiate the claims. iii In addition, isolating the exact cause of wear and tear on a vehicle can be difficult, whether it was caused by the relatively infrequent crossing of speed humps or the crossing of other frequent undulations in a roadway network, such as potholes, manhole covers, drainage dips, etc. … A speed cushion (also known as speed lump or speed pillow) has cushions placed longitudinally in the roadway specifically to match the wheel tracks of fire vehicles (see Figure 5.1) and provide a link to section 3.11 – Speed Cushion. Field tests have shown speed cushions to reduce general vehicle speeds while providing little to no delay to fire vehicles. vi …

• Q+A: Bumps, Humps, Cushions, Tables — What’s the Best Way to Slow Down Traffic?

The gap between humps/tables is specifically designed to enable a vehicle (usually emergency vehicles and buses) to pass through without being much affected.

Despite the evidence, the claim that speed cushions impede fire trucks resurfaces regularly in local debates. I think this persistence likely stems from a few factors.

First, people tend to conflate different traffic calming devices—older concerns about speed humps delaying emergency vehicles get applied to speed cushions, even though cushions are specifically designed with gaps that match the wider axle of fire trucks. Second, the potential cost of a delayed emergency response is vivid and easy to imagine, while the steady toll of pedestrian injuries and deaths from speeding is diffuse and statistical—making the hypothetical risk of calming feel larger than the proven risk of fast traffic. Finally, when lives are at stake, even a theoretical few-second delay carries emotional weight that data struggles to counteract.