How Speed Limits Impact Safety

Here’s a look at how lowering the speed limit by even 5 mph changes a motorist’s behavior, according to research from the Insurance Institute for Highway Safety.

Most people readily admit to driving over the speed limit:⁸

• Half of drivers say they have driven 15 mph over the speed limit on a freeway.
• Nearly half say they have driven 10 mph over the limit on a residential street.

We all have somewhere to be, yet speeding endangers everyone around you. In 2017, speeding accounted for more than a quarter of traffic fatalities (nearly 10,000 people).⁹ Amica encourages all drivers to obey posted speed limits and to consider the impact speeding can have on themselves and other travelers.

Rising speed limits over the past 25 years have only made the problem worse. A 5 mph-increase in the maximum speed limit was associated with an 8 percent increase in the fatality rate on interstates and freeways, and a 3 percent increase on other roads.³

To make streets safer, some cities, including Boston, New York and Seattle, have lowered speed limits – and the results are surprising. Drivers in Boston slowed down when speed limits were decreased just 5 mph.⁴

Amica asked Wen Hu, a senior research transportation engineer for the Insurance Institute for Highway Safety, about the results from the Boston study. Hu says that if there are fewer vehicles traveling at excessive speeds on urban roads, fewer severe and fatal injuries to non-motorists can be expected.

The difference between 30 mph and 25 mph might not seem like a lot, but a pedestrian has a 70 percent chance of survival if hit by a vehicle moving at 25 mph. That decreases to less than 20 percent at 31 mph.¹⁰

Hu adds that lowering the speed limit, even by just 5 mph, was shown to reduce the proportion of drivers who often travel at higher speeds. “The lower speed limit slows down the fastest-traveling drivers,” Hu says.

Worried safe speeds mean longer trips? Don’t be. Traveling between intersections (about .62 miles) at 19 mph compared to 31 mph only adds 18 seconds of travel time.¹⁰ If you’re driving 5 miles, traveling at 30 mph instead of 25 mph will save you only 2 minutes, Hu says. “It’s not a big difference in travel time.”

Whatever the situation may be, plan ahead to allow for extra time to get to your destination safely. If your vehicle is in a collision that causes injury or damage, learn how liability coverage protects you.

• Traffic Safety Facts: Speeding, National Highway Traffic Safety administration, 2019.
• Impact Speed and a Pedestrian’s Risk of Severe Injury or Death, AAA Foundation for Traffic Safety, 2011.
• Speed Limit Increases Are Tied to 37,000 Deaths Over 25 Years, Insurance Institute for Highway Safety, 2019.
• City Drivers Slow Down for Lower Speed Limit in Boston, Insurance Institute for Highway Safety, 2018.
• Design Speed, National Association of City Transportation Officials, 2019.
• Vehicle Stopping Distance and Time, National Association of City Transportation Officials, 2019.
• CMV Driving Tips – Too Fast for Conditions, Federal Motor Carrier Safety administration, 2015.
• 2017 Traffic Safety Culture Index, AAA, 2018.
• Speeding, National Highway Traffic Safety administration, 2019.
• The Need for (Safe) Speed: 4 Surprising Ways Slower Driving Creates Better Cities, World Resources Institutes, 2017.