What Are Speed Bumps Used For?

We’ve all experienced that sudden jolt of accidentally going over a speed bump too quickly. Those little lumps in concrete exist to ostensibly get people to go slower… at the expense of their car’s shock absorption systems. Nowadays, though, there are a few different options. Each type of design used to slow cars down on asphalt paving has a slightly different effect. Read on to find out about the design of speed bumps and how effective they are.

Speed Bumps

This is arguably the most aggressive way to get a car to slow down. Also known as traffic thresholds, sleeping policemen, or speed breakers, they are designed to slow down traffic. The defining feature of speed bumps is that they are higher, and significantly less long than other speed-lowering mechanisms. As you probably know if you are reading this, the effect of going over a speed bump is a jarring experience when too fast. At best, it’s a bit unnerving and the vehicles shock absorbents take the brunt of it. At worst, for example in a lowered car, the car bottoms out. Important machinery on the underside can get scraped, damaged, or broken off. This is especially a danger for “lowered” cars, that have their surfaces closer to the road.


Unfortunately, speed bumps are used privately most often. This means that they do not feature specific design parameters. They vary in height, length, and placement. However, there are a few defining features in the US at least.

  • Height is usually 3-6 inches.
  • Length is usually 1-3 feet.
  • Width can be one or two lanes, rarely more than two.
  • Placement:
    • Before stop signs.
    • Before intersections.
    • At dangerous locations in roadways.
    • At locations that see a lot of pedestrian traffic.
  • Materials: asphalt, concrete, rubber.
  • Costs: $700 to $6,900. The average cost is $2600. This wildly varying price depends on road width, drainage, height of the speed bump, and its design.

Design purpose

Ideally speed bumps are designed to make cars slow down to about 25 miles an hour or lower, sometimes down to 2-5 miles per hour. They are mainly used on private streets and parking lots. Many public streets do not allow them.


  • Aggressively slow down fast drivers.
  • The threat of damage to a vehicle is a major factor in slowing down drivers.
  • Easy to install and replace.
  • They remind drivers to check for pedestrians and stop signs.
  • Reduction of rear-end collisions.


  • Slow response time for emergency vehicles.
  • May divert traffic to other streets that are not designed for high volumes of vehicles.
  • Can increase noise pollution for residents of areas with speed bumps.
  • Vehicle damage.
  • Require more materials, including signs, street lighting, and striping.
  • If they lose color they become hard to see for motorists. This means they can pose a larger physical danger to drivers and vehicles.
  • Cause problems for public transit vehicles (like buses).
  • Discomfort for drivers.
  • Can actually distract drivers.
  • In extreme cases can damage the spine.

As you can see, there are quite a few problems posed by speed bumps. And some of the reasons that they are effective are also disadvantageous.

How effective are they?

As traffic volumes increase, traffic accidents go up commensurately. In urban and suburban areas, traffic flow peaks during rush hours. From about 7:00 AM to 10:00 AM, and then again from about 4 PM to 7 PM, traffic is at its highest levels. During these times, it becomes extremely difficult to monitor traffic manually.

Speed bumps have their uses, no doubt, but where are they best used? What is their statistical benefit? Do they really slow people down over all? Well, the answer to that is more difficult than you think. Because speed bumps are used in higher-traffic areas, it’s difficult to measure. During bumper-to-bumper traffic, people are usually traveling well-below the speed limit. It’s hard to measure speed bump effectiveness in terms of traffic speed.

What we can measure though, are the rates of collisions in areas with speed bumps. Children are particularly at-risk from fast-moving traffic. They don’t know, or always obey the laws of the road, and they are smaller and harder to see. Finally, they are known for spontaneously doing things — like running into the street, crossing without looking, or jumping out from behind cars. An American Journal of Public Health Study found that when speed bumps are installed in a neighborhood, there was a 53-60% reduction in injury or death of children struck by a vehicle. Although that’s only one study, it seems to pretty effectively provide evidence that speed bumps do make a neighborhood safer.

Why are speed bumps important?

Frankly, speed kills. A study from Seattle by the US Dept. of Transportation showed that speed contributed to 42% of the city’s fatal accidents. That’s almost half of car crashes that kill people being related to over speeding.

What about other options?

If speed bumps feel uncomfortable, unsightly, or not effective enough, there are plenty of other choices. Crosswalk enhancement, speed tables, raised intersections, and more can help slow down traffic. These methods vary from less aggressive bumps, like speed humps and raised intersections, to better signage.

Make your roadway safer

If you are interested in making your driveway, parking lot, or private road a safer place, then Reliable Paving is who to call. We can install speed bumps, speed humps, and ensure that your signage and striping is as visible as possible. Contact us here today. We will be happy to assess your asphalt paving and figure out what the best traffic control solution for you is. If you want paving contractors with 35-plus years of experience, a team big enough to handle any job, and relentless customer service, go with Reliable.