Speeding's Impact on Injury & Mortality

Degree that Speeding is Known as a Risk Factor for Motor Vehicle Injury and Fatalities

Increases in speed increase both the likelihood of a crash and the severity of that crash (World Health Organization, 2016). The National Highway Traffic Safety Administration (NHTSA) reports that both exceeding posted speed limits (EPSL) and driving too fast for conditions (DTFFC) impacts the rates and severity of crashes. In fatal crashes, 55% of the speed-related crashes were due to EPSL while 45% were due to DTFFC. On the other hand, among injury causing speed-related crashes, most (74%) were due to DTFFC, while only 26% of the crashes were due to EPSL (NHTSA, 2009).

Speed is a key factor in survivability in a motor vehicle crash, especially for those not protected by the safety systems inside of the vehicle: Pedestrian survivability of a car impact decreases dramatically as the car’s speed increases: the risk of an adult dying is about 10% when hit at 20mph, 50% when hit at 30mph, and 90% when hit at 40mph (Figure 2; Dwyer, 2015). The risk of injury and death increase with age and speed (Tefft, 2011); ProPublica has an interactive website where visitors can manipulate the age of a pedestrian and speed of a driver to see the risk of death based on this data (Groeger, 2016).

Figure 2. Visual representation of speed’s impact on pedestrian survivability

The extent to which the general public is aware of speed’s impact on crash frequency and severity may be limited. People know that speeding can be bad, but they don’t know how bad it is. Given news attention and billboards, the general public might think that distracted or drunk driving are the leading factors in roadway crashes. Even if the general public knows, in some small way, that speeding is dangerous, it does not appear to impact behavioral choices or desires. In a nationwide survey by the NHTSA, one-third agreed with the statement “I enjoy the feeling of speed,” and more than half said they often get impatient with slower drivers (Schroeder, Kostyniuk, & Mack, 2013). Accordingly, Americans regularly exceed the speed limit: A 2003 survey of four US states found 11–78% of drivers exceeded 55 mph speed limits by 15 mph or more and in two states with 75 mph limits on rural interstates, 10–24% of drivers drove faster than 80mph (NHTSA, 2002).