Speeding and Speed Management
Characteristics and problem size: Speeding. NHTSA defines a crash to be speeding-related if any driver involved in the crash is charged with a speeding-related offense or if a police officer indicates that racing, driving too fast for conditions, or exceeding the posted speed limit was a contributing factor in the crash. Speeding-related fatalities have generally decreased over the last decade, as shown in the figure below. In 2018 there were 9,378 speeding-related fatalities, a decrease of 6% from the 9,947 fatalities in 2017 (NCSA, 2020). Speeding is a contributing factor for 26% of fatalities in motor vehicle traffic crashes in the United States, a percentage that decreased from 31% since 2009. NHTSA has developed a webpage to visualize speeding-related fatal crashes by location, time-of-day, road type, and other factors (https://icsw.nhtsa.gov/nhtsa/fars/speeding_data_visualization/).
Source: NCSA (2020)
Younger drivers, particularly young males, continued to be the most likely to be identified as speeding in fatal crashes in 2018 (NCSA, 2020). In 2018 nearly one-third (30%) of male drivers in the 15- to 20-year-old age group involved in fatal crashes were speeding at the time of the crashes, compared to 18% for the female drivers in the same age group. Other risk factors associated with speeding in 2018 included driver alcohol use, lack of seat belt usage, driver not being properly licensed, and nighttime hours. In 2018 some 31% of all motorcycle riders (operators) involved in fatal crashes were speeding, compared to 18% of passenger car drivers, 14% of light-truck drivers, and 7% of large-truck drivers.
Speeding is legally defined by States and municipalities in terms of a “basic speed rule” and statutory maximum speed limits. The basic speed rule generally requires drivers to operate a vehicle at a speed that is reasonable and prudent for roadway conditions. Making a determination to take enforcement action is at the LEO’s discretion, which may be impacted by weather, surface conditions, traffic volume, and special locations (e.g., work zones, school zones, or other environmental conditions). Statutory speed limits set maximum limits for different types of roads, and generally apply to all roads of that type even when the limits are not posted. These limits can be superseded by limits posted for specific roadway segments, usually determined by engineering studies. Special Report 254 of the Transportation Research Board, which reviewed much of the past research regarding the effects of speed and speed limits on crashes, describes the reasons for setting speed limits and other actions for managing travel speeds (TRB, 1998). The TRB guide contains much valuable information that is still very relevant for setting limits and managing speeds.
A document prepared by the Global Road Safety Partnership (Howard et al., 2008) with input from U.S. experts, updates speed management guidance based on more recent knowledge, and describes the evolution of practices used by countries with a zero deaths vision and framework. For example, practices used in such countries no longer rely on the 85th percentile or other operating speed distributions, but set limits according to injury minimization principles. A detailed description and comparison of these and other methods is provided in Methods and Practices for Setting Speed Limits: An Informational Report (Forbes et al., 2012), prepared by the Institute of Transportation Engineers in cooperation with FHWA. In the United States, Vision Zero is primarily an initiative targeting local jurisdictions to get them to adopt speed-management policies and roadway design practices that encourage driving at speeds that are less likely to result in serious injuries or fatalities. As of January 2018 thirty-five cities had adopted policies from this initiative (Vision Zero Network, 2018).
Speeding can be dangerous on all types of roads, but particularly on non-interstate rural and urban roadways. In 2018 there were 41% of speed-related fatalities that occurred on non-interstate rural roadways, another 44% on non-interstate urban roadways, 9% on interstate urban roadways, and 5% on interstate rural roadways (NCSA, 2020).
Speeding is also common. A 2007 nationally representative observational survey for NHTSA estimated that, in free-flowing traffic, 48% of drivers on limited access highways were exceeding the speed limit, 60% were exceeding speed limits on other major arterials, and 61% were exceeding speed limits on minor arterials and collectors (Huey et al., 2012). This percentage range is comparable to findings from a study among Organisation for Economic Co-operation and Development countries, which showed that 40 to 50% of vehicles were driving above the posted speed limit (WHO, 2017).
In the 2007 NHTSA survey, many drivers were exceeding the posted speed limit by more than 10 mph on all these road types, including 16% on limited access roads, 14% on major arterials, and 15% on minor arterials and collectors. NHTSA’s nationally representative observational survey was repeated in 2009, and found that free-flow speeds on limited access highways increased by 6 mph as compared with 2007 (Huey et al., 2012). The percentage of drivers exceeding the speed limit by more than 10 mph increased from 16% in 2007 to 19% in 2009 on limited access highways. There was little change in speeds on major and minor arterials from 2007 to 2009. Slight declines (0.3 to 0.5 mph) in mean speeds were observed for major arterials, with slight increases (0.2 to 0.4 mph) on minor arterials and collectors. The percentage of drivers exceeding the speed limit by more than 10 mph increased on minor arterials and collectors (from 15% to 16%) from 2007 to 2009. A more recent survey compared data from 2009 to 2015 (NHTSA, 2018). Mean speed on the major arterials increased by 3.1 mph from 2009 to 2015, whereas only a minor change (-0.1 mph) was observed on limited access roads. In terms of percentage of vehicles surpassing the speed limit, the percent exceeding by more than 10 mph on major arterials increased from 13.3% in 2009 to 18.1% in 2015, whereas on the limited access roads, the percent exceeding by more than 10 mph was almost the same (20.1% in 2009 and 20.3% in 2015). Traffic Tech summaries are available for all three studies (NHTSA, 2012a; NHTSA, 2012b; NHTSA 2018).
Drivers themselves also report high percentages of speeding. NHTSA’s most recent nationally representative survey of drivers conducted, the National Survey of Speeding Attitudes and Behaviors (NSSAB), suggests that some trends in driver attitudes and speeding behaviors may be improving (Schroeder et al., 2013). In 1997 some 31% of surveyed drivers reported passing other cars more often than other cars passed them. In 2011 about 27% of surveyed drivers reported passing other drivers more often. The percentage of drivers who reported that they enjoy the feeling of driving fast also declined, from 40% in 1997 to 27% in 2011. In addition, the percentage who thought the faster they drive, the more alert they are decreased (from 29% in 1997 to 15% in 2011), as did the percentage who reported that they try to get where they are going as fast as they can (from 30% in 1997 to 21% in 2011). A few trends did not improve: Driver impatience with slower drivers was about the same in 2011 (61%) as in 1997 (60%). In addition, the proportion of drivers stopped by police for speeding was fairly similar over these different survey periods. In 1997 some 9% of drivers reported having been stopped by police for speeding within the past 12 months, 11% reported being stopped in 2002, and 9% reported being stopped in 2011. Other driver beliefs were sometimes at odds with each other. For example, two-thirds of drivers agreed strongly that “It is unacceptable to exceed the limits by more than 20 mph,” and 91% agreed that “Everyone should obey the speed limit because it’s the law.” Yet 82% agreed that “People should keep up with the flow of traffic,” and 51% agreed that speeding tickets have more to do with raising money than they do with reducing speeding.
Drivers in the 2011 NSSAB were grouped (by analysis) into three clusters or categories according to their responses on six questions about speeding behavior (Schroeder et al., 2013). Of the sample, 30% were classified as “frequent” speeders. Forty percent of the sample of drivers was classified as “sometime” speeders, and 30% as “non-speeders” or drivers who rarely speed. The vast majority of speeders reported that they often pass others, speed by at least 15 mph on multi-lane divided highways and two-lane highways and by at least 10 mph on residential streets, and were five times more likely to have been stopped for speeding in the past 12 months than non-speeders. Unfortunately, speeders also reported taking other risky actions more often than non-speeders and sometime speeders. Speeders reported talking on the phone or texting more often, using seat belts less often, and drinking before driving slightly more often than the other groups. Speeders also tended to be younger compared to non-speeders and sometime speeders, and to view the need to do something about speeding as less important. Across all drivers, however, 87% of surveyed drivers thought it was very important (48%) or somewhat important (39%) that something is done to reduce speeding. A recent study re-examined the NSSAB typology, and compared driver types with their speeding conviction history. The study involved a survey of Idaho drivers with 0, 1, or 2+ speeding convictions in the past 3 years (Richard et al., 2017). The study validated the notion of different types of speeders, and found that the frequent speeder group was significantly associated with a greater number of speeding convictions. Driver attitudes were also related to speeding. Survey responses reported that the frequent speeder group was more accepting of risky driving behaviors (such as drinking and driving, not using a seat belt, or red-light running) than other groups that sped less. Another study characterized motivations and types of speeders using naturalistic driving data (Richard et al., 2012, for a summary of findings; also see Richard et al., 2013a, 2013b). Speeders were classified into four general patterns based on the percentages of trips with speeding and the average amount of speeding per trip. The four patterns were: (1) incidental or infrequent speeders (few trips with speeding and little speeding on those trips); (2) situational speeders (few trips with speeding but a lot of speeding on those trips); (3) casual speeders (many trips with speeding but only small amounts of speeding on those trips); and (4) habitual speeders (speeding on most trips with a lot of speeding on those trips). Young males and young females in urban settings and young males in rural settings were more likely than older drivers to have trips with speeding. Follow-up focus groups revealed some interesting differences between speeding drivers and those who did not speed. Particularly interesting was the drivers’ perception of the meaning of posted speed limits. Drivers that sped a lot considered posted limits to be guidelines rather than strict limits, while the non-speeders considered speed limits to be firm limits not to be exceeded.
A follow-up analysis using the naturalistic driving data described above found evidence for a specific type of speeding behavior that had more aggressive characteristics, such as high maximum speeds and high speed variability, in comparison to other types of speeding behaviors (Richard et al., 2016). Moreover, drivers that engaged in this type of aggressive speeding differed from other drivers in terms of self-reported measures. In general, these drivers were significantly more likely to report engaging in other risky behaviors such as tailgating, taking risks when in a hurry, and cutting off other drivers. Taken together, this analysis based on naturalistic driving behaviors suggests that aggressive driving may arise from persistent driver attitudes and personality traits.
While the legal definitions of speeding include exceeding the posted speed limit, driving too fast for existing conditions, and racing, speeding becomes an element of aggressive driving when a vehicle’s speed substantially exceeds the prevailing travel speeds of other vehicles, and other driving behaviors contribute to unsafe conditions, e.g., tailgating, weaving, and rapid lane changes. Speeding is a more clearly defined problem than aggressive driving, and strategies to reduce speeding (and other serious traffic law violations) may provide a means to address the problem of aggressive driving. However, speeding is among the most complex traffic safety issues to address and requires a multi-disciplinary approach to effectively manage. Enforcement is an important element in developing a strategy to address speeding, as are considerations of engineering issues and public education and communications efforts.
Characteristics and problem size: Aggressive and risky driving. Aggressive and risky driving actions are also perceived to be common, although they are difficult to measure accurately. In NHTSA’s 2002 survey of speeding and unsafe driving behaviors, 40% of drivers reported that they sometimes enter an intersection “just as the light turned from yellow to red,” and 11% said they often did this. In the same survey 10% reported sometimes cutting in front of another driver, and 2% said they often did this (NHTSA, 2004). About one-third (34%) of drivers reported that they feel threatened by other drivers at least several times monthly. The 2011 NSSAB did not ask about these other risky behaviors. NHTSA has estimated that two-thirds of traffic fatalities involve behaviors commonly associated with aggressive driving such as speeding, red-light running, and improper lane changes (NHTSA, 2001). Similarly, the AAA Foundation for Traffic Safety estimated that 56% of fatal crashes involved one or more driver actions typically associated with aggressive driving, the most common being excessive speed (AAAFTS, 2009).
Aggressive driving is generally understood to mean driving actions that markedly exceed the norms of safe driving behavior and that directly affect other road users by placing them in unnecessary danger. Aggressive driving may involve driver anger, attempts to gain an advantage over other drivers, and deliberate violations and deviations from normal traffic speeds (Neuman et al., 2003). It has proven challenging to arrive at a consensus for a theoretical definition of aggressive driving, and hence to come up with a working definition. Not every moving violation is considered to be aggressive driving. However, violations that encroach on others’ safe space, such as driving much faster than prevailing speeds, following too closely, making unsafe lane changes, and running red lights, either on one occasion or over a period of time, may indicate a pattern of aggressive driving. Although some States have passed laws criminalizing aggressive driving, it should not be confused with road rage, which is an intentional assault by a driver or passenger with a motor vehicle or a weapon that occurs on the roadway or is precipitated by an incident on the roadway.
Causes of aggressive driving can include both personal influences, such as peer or social pressures, and environmental triggers. A predisposal to styles or habits of driving that frequently puts others at risk might be the norm for a small proportion of drivers, while others may be provoked to drive aggressively, at least occasionally, by exceptional congestion, work zone delays, poorly timed traffic signals, being late, and other frustrating conditions. Other drivers’ actions are also sources of irritation for “reactive” style drivers. More than half of drivers in one study reported that they would react aggressively, particularly to being impeded, by others’ reckless driving or actions perceived as directly hostile (Björklund, 2008). Other life stressors, such as combat deployments, may also contribute to aggressive driving (Sarkar, 2009). Driving actions are, however, ultimately under individual drivers’ control. Behavioral countermeasures for speeding and aggressive driving must reinforce and help teach such control.