Cushions, tables and bumps: Speed-calming devices improve neighborhood safety

Pop quiz: What’s 6 feet long, 3 inches high and designed to slow drivers in a residential neighborhood?

If you said, “speed cushion” or “speed table,” you guessed correctly.

Speed cushions, more commonly known as “speed bumps,” are just one of the mechanisms the City uses to calm traffic in residential areas. They are effective in deterring drivers who speed or use residential streets as a cut-through between major arterials.

A graphic of vehicle impact speed versus pedestrian injuries.

This graphic from the Federal Highway Administration shows a correlation between vehicle impact speed and pedestrian injuries. Traffic calming mechanisms like speed cushions help reduce speed in residential neighborhoods, which enhances safety for pedestrians and cyclists.

The Federal Highway Administration (FHWA) claims traffic-calming measures like speed cushions can reduce vehicle crashes and create an equitable balance between vehicles and pedestrians. After all, no one wants to walk or bike on dangerous road.

A Portland Bureau of Transportation study shows annual crashes dropped by 39% on streets where speed cushions were installed. Crash injuries decreased by as much as 46%.

Other benefits include improved air and noise levels because slower vehicles make less noise and emit fewer pollutants. Finally, traffic calming measures can reduce crime because speed cushions prevent a criminal from making a fast getaway.

By the numbers

How many speed bumps and tables are there in Huntsville?

According to Nicholas Nene, Huntsville’s Deputy Director of Traffic Engineering, there are 264 speed cushions and 162 speed tables in the City limits.

What’s the difference between the two? Speed cushions vary in length but are generally 6-7 feet wide, 3 inches at their highest point and typically made of recycled rubber tires. Speed tables extend across the width of the road and ramp up to a height of 3 to 3 ½ inches and are formed from the asphalt in the roadway.

The process

What’s involved in having a speed bump or speed table installed?

As you might guess, installing any device on a City street that affects traffic doesn’t happen overnight. It usually starts with a citizen concern of vehicles traveling too fast through a neighborhood.



Generally, speed cushions and tables are only installed on residential streets with a posted speed limit of 25 mph. The streets also can’t be considered primary response routes by the Huntsville Fire & Rescue Chief. Nene said there are other considerations, too.

“The criteria for speed cushions is based on 500 cars per day and an 85th percentile speed of 35 mph or more in both directions of travel, meaning 15% of vehicles are traveling more than 35 mph in both directions,” he said. “Both criteria have to be met, not just one.”

He said if volume and speed criteria are met, the City’s project lead will be provided a petition of all addresses on the street.

“At least 75% of residents on the street must sign a letter stating they are in favor of the installation,” Nene said. “They are installed if funding is available.”

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