Speed Bumps Get Smart

By Tom Ripley

What is dumber than a speed bump? It's hard to imagine anything dumber than those elevated areas of roadways that force drivers to slow down, but now speed bumps are getting smarter. In fact they are so smart that you can't call them speed bumps anymore. Instead, the preferred term is "traffic calming device," which, while popular in Europe for decades, is still in its infancy stages in the U.S. But as time goes on, more and more cities across America have begun installing these devices as a solution to speeding traffic on residential roads.

What makes them smart? Well, first, they come in a variety of configurations depending upon need. And, second, they do their job -- slowing traffic -- silently and with no human intervention whatsoever. The newest of them are also removable, so that municipalities can make way for snowplowing in the winter.

First, let's define our terms. All traffic calming devices are not the same. For example, while we in the general public tend to lump all such devices under the speed bump label, there are differences between the devices. As defined by Traffic Logix, a key supplier of such devices in the United States, speed bumps are primarily used off the road in parking lots or alleyways. The speed bumps manufactured by Traffic Logix are 2.25 inches high and four or six feet long. 

In contrast, there are also speed humps. These are considered the most common traffic calming devices, and they are used to influence drivers to slow excessive vehicle speeds and perhaps avoid the route entirely. Circular speed humps are often installed in a series to create still greater irritation to drivers who negotiate them too fast, and they are most often used on residential streets, not highways or thoroughfares. They are designed to slow traffic to between 10 and 20 miles per hour. You'll often see them installed a mid-block, away from intersections. Studies conducted by the Institute of Transportation Engineers found that the installation of speed humps reduced traffic volume by 18 percent and collisions by 13 percent. Traffic Logix speed humps are either three or four inches high.

A similar device is referred to as a "speed table." Designed not to slow traffic as drastically as a speed hump, the flat-topped speed tables might slow traffic to the 20-35 miles per hour range. The long, horizontal-topped speed tables can often accommodate an entire car, so drivers are not forced to slow as much when negotiating them. Like speed humps, studies suggest that speed tables significantly reduce accidents.

The newest available devices are called speed cushions or speed lumps, and their major advantages is that they can slow car traffic without slowing the response time of emergency vehicles. Designed with several small speed humps in a group, they force cars and light trucks to slow to 15-25 miles per hour, but, because of their placement on the road, they allow larger emergency vehicles with wider tracks to proceed unhindered.

One city that has bought into the technology is New Haven, Conn., which has purchased and installed four speed humps and six speed lumps. "It might be sexier to go after people with guns," said Erin Sturges Pascal, a member of the board of Aldermen of the city, "but speeding cars are equally as deadly." She sees the traffic calming devices as ways to counteract anti-social driving behavior.

An expert on anti-social behavior, Driving Today Contributing Editor Tom Ripley writes about the auto industry, safety and la condition humaine from his home in Villeperce, France.

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