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1. Is speeding really a safety problem?
Yes.
Speeding reduces the time drivers have to avoid crashes and lengthens stopping distances, increasing both the likelihood of crashing and the severity of the crashes that do occur. According to the National Highway
Traffic Safety Administration (NHTSA), speeding is one of the most prevalent reported factors associated with crashes. Speed is a factor in 30 percent of all fatal crashes, killing an average of 1,000 Americans every
month. In 1999, more than 12,000 people died in speed-related crashes. NHTSA estimates the economic cost to society of speed-related crashes to be $28 billion each year. Health care costs alone are about $4 billion per
year.In a high-speed crash, a passenger vehicle is subjected to forces so severe that the vehicle structure can't withstand the force of the crash and thus can't sufficiently protect occupants from serious
injury. Likewise, the performance of restraint systems such as airbags and safety belts are compromised in high-speed crashes. This also is true of roadside hardware and safety features such as barriers, crash cushions,
and bridge rails, which are designed to reduce crash severity by absorbing crash energy or redirecting errant vehicles away from stationary roadside objects. Infrastructure design standards accommodate a range of
vehicle impacts, but they can't provide adequate protection for people in vehicles traveling at very high speeds. Higher truck speeds bring additional problems including increased tire tread wear, a rise in
tire-weakening operation temperature, longer stopping distances, and increased brake wear. Roadway design factors, including how far ahead a driver can see, are compromised if vehicles travel faster than
circumstances warrant. Other vehicles and pedestrians are put at risk by speeding drivers whose distances they may not be able to judge accurately. Studies have shown that drivers who run red lights are likely to be
speeding and that motorcyclists who crash with other vehicles making left turns also are likely to be speeding. back to questions 2. What is the relationship between how fast a car is going
and what happens in a crash?
The higher the travel speed, the greater the risk of serious injury or death in a crash. Vehicles and
their occupants in motion have kinetic energy that is dissipated in a crash. The greater the energy that must be dissipated, the greater the chances of severe injury or death. The laws of physics tell us that crash
severity increases disproportionately with vehicle speed. A frontal impact at 35 mph, for example, is one-third more violent than one at 30 mph. Speed influences crashes in four basic ways:
1.It increases the distance a vehicle travels from when a driver detects an emergency until the driver reacts 2.It increases the distance needed to stop a vehicle once an emergency is perceived.
3.Crash severity increases by the square of the speed so that, when speed
increases from 40 to 60 mph, speed goes up 50 percent while the energy released in a crash more than doubles. 4.Higher crash speeds reduce the ability of vehicles, restraint systems, and roadway hardware such as guardrails, barriers, and impact attenuators to protect occupants. back to questions
3. Who speeds most?
Young drivers speed more
often than older drivers. In a study of drivers on limited access highways, high-speed drivers were more often male and more often judged to be younger than 30. Studies in California have found that the rate of speeding
violations per mile traveled is at least three times as high for drivers 16-19 years old as it is for drivers age 30 and older. Although speeding is a problem among all driver age groups, the crashes and violations of
young drivers are much more likely to be related to speed than is the case for drivers of other ages -- and the motor vehicle crash death rate per 100,000 people is especially high among 16-24 year-olds. A NHTSA
analysis found that the relative proportion of speed-related fatal crashes decreases with increasing driver age. About 37 percent of all drivers ages 14-19 involved in fatal crashes were in speed-related crashes, but
the percentage among drivers 70 and older decreased to 7 percent. At all ages, male drivers are more likely than female drivers to be involved in speed-related fatal crashes. back to questions 4. Does the speed limit matter? Don't drivers speed anyway?
Many drivers tend to drive
somewhat faster than posted speed limits, no matter what the limits are. Although people often opt to travel somewhat faster than the posted limit, they do not completely ignore it but choose a speed they perceive as
unlikely to result in a ticket. The more important speed-related safety issue on freeways involves the proportion of vehicles traveling at very high speeds, not the proportion violating the speed limit. The Institute's
frequent monitoring of free-flowing travel speeds on interstate highways posted at 55 mph and speeds on roads with 65 and 75 mph limits shows that, in general, higher speed limits lead to greater proportions of cars
traveling at very high speeds. For example, in New Mexico, which raised its limits to 65 mph on rural interstates in 1987, the proportion of motorists exceeding 70 mph grew from 5 percent shortly after
speed limits were raised to 36 percent in 1993. After speed limits were further increased to 75 mph in 1996, more than 42 percent of motorists exceeded 75 mph. In Maryland, which retained 55 mph limits on rural
interstates until 1995, the proportion traveling faster than 70 mph remained virtually unchanged at 7 percent during 1988-93. By 1994, 12-15 percent of cars were exceeding 70. In neighboring Virginia, which switched to
65 mph limits, the percentage exceeding 70 mph went from 8 percent in 1988 to 29 percent by 1992 and 39 percent by 1994. back to questions 5. Does research show that slightly faster speed
limits would reduce crashes?
No. Advocates of higher speed limits have claimed that research on speed variation indicates
faster speeds are not hazardous. They cite David Solomon's research from the mid-1950s and similar studies that seem to show an increase in crash likelihood among drivers traveling slower than the average speed and a
minimum of crashes at 5-10 mph above the average speed. However, the crash-involved drivers in these studies reported their travel speeds. It is well known that drivers exceeding speed limits are likely to deliberately
underestimate their speeds. Such underestimation can account for much of the apparent underinvolvement of moderately high-speed drivers in crashes. In addition, later research found that simply removing the crashes
involving intersections and turning maneuvers eliminated the exaggerated overinvolvement of slower drivers in crashes. More important, the Solomon research addressed only speed variation, not speed limits. Raising speed
limits raises average speeds as well. back to questions |
