More than a decade after the 1995 repeal of the 55 mph national maximum limit, the United States remains a nation of lawbreakers when it comes to speeding.
The latest Institute research reveals that travel speeds generally have risen on interstate highways and arterial roads. On some freeways, heavier traffic volume may hold down speeds. On others, speed cameras dissuade drivers from exceeding the posted limits. Horsepower comes into play, too, as automakers juice the engines of even the most ordinary vehicles in their lines.
To get an idea of travel speeds in 2007, the Institute collected speed data on urban, suburban and rural interstates in 8 metropolitan areas (Albuquerque, Atlanta, Boston, Denver, Los Angeles, Omaha, Tampa, and Washington, D.C.) and examined intercity stretches of interstates 30-50 miles outside 3 of the metro areas to see how travel speeds compared. Arterial roads also were monitored, adding to the speed picture.
Extensive violations on all kinds of roads
On urban interstates, the average speed of passenger vehicles (cars, SUVs, and pickups) in 2007 exceeded the limits in all 8 metro areas. On suburban and rural interstates, average speeds were faster than the limits in half of the metro areas. The proportion of passenger vehicles exceeding 70 mph on urban interstates ranged from 1 percent in Denver and Tampa to 38 percent in Albuquerque, while the percentage exceeding 75 mph on suburban and rural interstates ranged from 6 percent in Los Angeles to 49 percent in Tampa.
Many motorists also drove faster than the posted 65 or 70 mph limits on intercity segments of suburban and rural interstates near Washington, D.C., Atlanta, and Los Angeles. Outside Washington, where the limits are 65 mph, more than one-third of passenger vehicles traveled faster than 70 mph and 7 percent exceeded 75. Outside Atlanta, where limits are 70 mph, 19 percent of passenger vehicles were logged exceeding 70 mph and 3 percent surpassed 75.
Speeds were much faster on the Los Angeles intercity segment, where 86 percent of passenger vehicles surpassed the 70 mph limit, 35 percent traveled faster than 80, and 1 in 10 exceeded 85. At 78 mph, the average passenger vehicle speed was the highest the Institute ever recorded.
To gauge speeds beyond interstates, the Institute last year looked at arterial roads with posted limits of 40 or 45 mph in the metro target group, excluding Albuquerque. Arterial roads aren't built to the same safety standards as interstates and have much higher crash rates. Forty-five percent of deaths related to speeding in 2006 occurred on roads with limits of 45 mph or lower. Average speeds on the arterials exceeded posted limits, except in Atlanta, where they were slightly slower than the 45 mph limit. On a Boston arterial with a 45 mph limit, 62 percent of passenger vehicles traveled faster than 60 mph. On a Washington, D.C., arterial with a 45 mph limit, 25 percent of passenger vehicles exceeded 60 mph. A Denver arterial with a 40 mph limit had the slowest speeds. Still, 3 percent of vehicles surpassed 50 mph.
Large truck speeds
On average trucks tend to go slower than passenger vehicles. In 2007, the proportion of large trucks exceeding 70 mph on urban interstates ranged from none in Tampa and Denver, where limits are 55 mph, to 21 percent in Omaha, which has a 60 mph truck limit. On suburban and rural interstates, the proportion traveling faster than 75 mph ranged from 1 percent in Los Angeles, which has a 55 mph truck limit, to 29 percent in Tampa, where the limit is 70. On intercity segments of rural interstates, 5 percent of trucks traveled faster than the 70 mph limit in Atlanta, while 15 percent surpassed 70 mph in Los Angeles, where the truck speed limit is 55 mph. Outside Washington, D.C., where the truck limit is 65 mph, 18 percent traveled faster than 70 mph.
"During the 1990s, opponents of the national maximum speed limit argued that since drivers were already exceeding posted limits, states should be able to set limits to match then-current travel speeds," notes Anne McCartt, Institute senior vice president for research. "The result was faster travel and more highway deaths."
Posting higher speed limits generally means more vehicles will go very fast. This is risky because faster speeds increase the frequency as well as the severity of crashes and help push up crash death rates (see Status Report special issue: speeding, Nov. 22, 2003). Speeding was cited by police as a contributor in about 32 percent of U.S. crash deaths in 2006, resulting in more than 13,500 fatalities.
Interstates: passenger vehicle speeds, 2007
|Suburban/rural interstates||Speed limit||Mean speed||Percent going faster than 75||Percent going faster than 80|
|Urban interstates||Speed limit||Mean speed||Percent going faster than 70||Percent going faster than 75|
|Denver||55||56||1||less than 1|
|Tampa||55||57||1||less than 1|
Arterials: passenger vehicle speeds, 2007
|Arterial roads||Speed limit||Mean speed||Percent going faster than 50||Percent going faster than 60|
|Atlanta||45||43||4||less than 1|
Trends over time
The Institute has been monitoring speeds on certain interstates for more than 20 years and began its metro speed study in 2003. Researchers that year recorded the highest average speeds they'd ever observed (see Status Report special issue: speeding, Nov. 22, 2003).
"Atlanta was the worst offender in 2003, with nearly 1 in 5 drivers exceeding 80 mph on an urban interstate with a 55 mph limit," McCartt says. "Speeds on urban expressways in Atlanta, Boston, and Denver have declined since then, while those in Albuquerque and Los Angeles have climbed."
The best long-term data come from Albuquerque. When the Institute began tracking speeds there in 1987, right after the limits on rural interstates were raised to 65 mph from 55, the mean passenger vehicle speed was 63 mph, with fewer than 1 percent of passenger vehicles going faster than 80. In 2007 the mean speed was 74 mph, and 14 percent of passenger vehicles exceeded 80 mph. New Mexico raised speed limits on rural interstates to 75 mph in 1996.
On urban interstates in 2007, passenger vehicle travel speeds were the highest the Institute had ever logged on these roads. Thirty-eight percent exceeded the 65 mph limit by at least 5 mph and 13 percent exceeded it by at least 10 mph. During 2003 and 2005, almost 1 of every 3 passenger vehicles traveled at least 5 mph faster than the posted limit.
These studies provide a clearer picture of travel speeds but not a complete one. Beyond the sites where they monitor speeds, Institute researchers can't say definitively whether speeds nationwide are up, down, or stable.
"In general we know that when traffic volume allows and drivers think the risk is low of getting a ticket, they tend to speed. And we know for certain that speeding persists as a major cause of highway deaths, even though today's vehicles do a good job of safeguarding occupants in crashes," McCartt says. In fact, deaths in crashes that occur at faster speeds offset some of the lives saved by more crashworthy vehicle designs and advanced safety features.
"Although speeding is a fact of life, speed limits do help keep travel speeds in check," McCartt concludes. "Tougher enforcement of posted limits, whether via traditional manpower or speed cameras, is key to persuading drivers to stick to the playbook."