Strategies to Reduce Speeding and Aggressive Driving

Speeding and aggressive driving actions, such as red-light running, involve traffic law violations. Therefore, deterrence through traffic law enforcement is the basic behavioral strategy that has been used to control them. This strategy involves the same components used to deter alcohol-impaired driving or seat belt nonuse: highly publicized and highly visible enforcement of practical, sound, and broadly accepted laws. Another important strategy involves setting appropriate speed limits using engineering practices that take into consideration the road segment’s design, vulnerable users, traffic operations, land use, and environmental conditions (NHTSA, FHWA, & FMCSA, 2014). Information on different speed limit setting approaches is described in Methods and Practices for Setting Speed Limits: An Informational Report (Forbes et al., 2012). Additionally, the NCHRP Guide for Addressing Aggressive-Driving Collisions (Neuman et al., 2003) suggests that successful anti-aggressive driving programs place an emphasis on enforcing all traffic laws. Such a strategy increases respect for all laws and the public’s expectation that traffic laws should be obeyed.

Speeding is a traffic safety problem that is national in scope, but requires local decision making and action to be managed effectively. Local communities are in the best position to make judgments in balancing risk against mobility, and are encouraged to use all the tools that are available to make determinations regarding speed management.

Speed enforcement is among the most common traffic enforcement conducted by law enforcement across the country. Sustained enforcement of all traffic laws is strongly encouraged, including speeding violations. The enforcement of traffic laws and attentiveness to traffic safety should be a core value and practice among LEAs in order to achieve results that contribute to the quality of life in communities that are impacted by the movement of traffic. A recent analysis of speeding-related traffic issues by the National Transportation Safety Board points to the need for cooperation across Federal, State, local jurisdictions, and LEAs towards developing legislation, guidelines, and data-driven reporting practices for successful speed management (NTSB, 2017). 

Specific action and decision making with respect to enforcement generally falls to the discretion of the LEO engaged with the traffic violator. While enforcement action is not always reported, it does reinforce the concept of consequences for unsafe driving and creates a perception of risk for drivers operating a vehicle unsafely. Enforcement actions for speeding violations should be fair, consistent with local or State statutes, and taken in the interest of preventing traffic crashes. Correspondingly, enforcement activity in locations with a demonstrable speeding/crash issue are ideally recommended for focused enforcement. 

To support fair, defensible, and reasonable enforcement of speed, speed limits should be established through appropriate engineering practices. Roadway design can take many forms and can manage the smooth and efficient movement of traffic based on the nature of the roadway. These practices include making determinations about appropriate and reasonable speed limits. 

Engineering measures may include the application of traffic calming roadway design, such as roadway diets, using devices, markings, and structures to slow traffic to increase safety, or support safety efforts near schools, parks, and other areas, particularly on collector and neighborhood roads (NHTSA, FHWA, & FMCSA, 2014; TRB, 1998; also see FHWA, 2009). “Self-enforcing” roadways is a related concept where roadways are designed in such a way as to encourage drivers to intuitively adopt speeds appropriate for the roadway without the need for posted speed limit signs (Neuman et al., 2009). This approach relies on geometric features and visual cues to shape driver speed selection towards speeds that feel safe and comfortable. 

Although such measures must be carefully implemented so as not to shift speeding or safety problems to other locations, they can be useful on both local streets and transition areas such as State highways that pass through towns or rural villages (Bagdade et al., 2012). Roundabout intersection designs and “road diets” [1] also reduce speed and crashes and can, at the same time, improve traffic flows in some situations (Rodegerdts et al., 2007; Harkey et al., 2008; Srinivasan et al., 2011). Well-timed and coordinated traffic signals can improve traffic flow and reduce red-light running and are potentially useful for managing speeds. Adequately designed turn bays and entrance and exit ramps can reduce improper merging and driving on the shoulder (Neuman et al., 2003, Strategy B1). Advance warnings of congestion or delays and well-designed and managed work zones may also decrease unexpected frustration. Intelligent Transportation System technologies such as real-time transit information, variable speed limits, variable message signs, traffic control warning devices, and other systems that respond to changing traffic and environmental conditions and provide motorists with timely information, also hold promise for improving mobility and safety by mitigating causes of delay and warning of hazardous conditions that require lower speeds. Company policies, backed up with speed monitors and logs or even speed regulators, can reduce commercial vehicle speeding. A variety of measures to reduce congestion, such as mass-transit, ride-sharing, or bicycle riding, can also diminish driver frustration that leads to aggressive driving (Shinar & Compton, 2004).

Vehicle technologies that interact with the environment, such as adaptive cruise control, ACC, and intelligent speed adaptation, hold promise. ACC works similarly to standard cruise control, except that, in addition to maintaining a speed set by the driver, a radar system in the front of the vehicle detects and responds to other vehicles in the lane ahead to maintain a safe following distance. Intelligent Speed Adaptation, or ISA, involves in-vehicle devices that “know” the speed limit through accurate speed limit mapping and vehicle location data, and provide a warning or active controls to help prevent speeding above limits (see Sections 2.3 and 3.1). These environmental and vehicular strategies are generally not included in this guide because SHSOs have little or no direct authority or responsibility for them. 

Any measures that can achieve reductions in average operating speeds, including lower speed limits, enhanced enforcement, and communications campaigns, as well as engineering measures, are expected to reduce fatal and injury crashes (AASHTO, 2010). Small changes in average speed are predicted to have a substantial impact. For example, a reduction of 3 mph in average operating speed on a road with a baseline average operating speed of 30 mph is expected to produce a reduction of 27% in injury crashes and 49% in fatal crashes (AASHTO, 2010; p. 3-57, Table 3E-2). The effects on injury and fatal crashes of changes in average roadway operating speed are also greater, as a percentage, at lower initial average speeds than at higher speeds. The table below reproduces Table 3E-2 from the Highway Safety Manual and shows crash modification factors (CMFs) for fatal and injury crash reductions. To determine the expected crash reductions for different changes in average speed, subtract the CMF from 1. In the example described above – a 3 mph reduction from an initial average operating speed of 30 mph – the CMF is .73, so 1 – .73 is .27, or a 27% reduction in injury crashes. Actual effects may vary depending on the type of countermeasure and other factors. No single strategy will be appropriate for all locations, and combinations of treatments may be needed to obtain speed limit compliance and achieve crash reduction goals.

Expected injury and fatal crash modifications by change in average operating speed*

*This table can be used to estimate expected changes in injury and fatal crashes (if no Crash Modification Factors are available) for treatments reducing average travel speeds of a road by the amounts listed.

Source: Reproduced from AASHTO (2010), p. 3-57; Table 3E-2. Crash Modification Factors for Changes in Average Operating Speed from Highway Safety Manual.

Speed management and the setting of appropriate speed limits requires a coordinated effort among State and local highway safety offices, engineering offices, and LEAs. A collaborative effort using a multi-disciplinary approach will support better informed and enforceable speed limits likely to have public and political support. Neuman et al. (2009) and other guides in the NCHRP report 500 series provide more detailed information and steps to develop comprehensive safety plans. For example, a comprehensive strategy may begin with data analysis to prioritize corridors, intersections or other areas with crash problems related to speeding or aggressive driving. Analyses may require, at a minimum, crash data and roadway inventory data, both of which are typically maintained and analyzed by State DOTs. Next steps should include identifying other important partners, establishing crash reduction goals, and performing additional diagnosis such as through interdisciplinary, roadway safety audits to identify the specific problems and potential solutions. Next, program developers should conduct economic and feasibility analyses to prioritize among alternate solutions and develop implementation plans. Finally, partners cooperate to implement engineering, enforcement and communications strategies to achieve the desired behaviors and target crash reductions. Combining appropriate countermeasures may achieve greater effects. Communications strategies are important to support enforcement and some types of engineering countermeasures. See Neuman et al. (2003) for specific examples of cooperative strategies on aggressive driving, and Neuman et al. (2009) for more information on speed limit setting, roadway design, traffic enforcement, and public information and educational strategies to reduce speeding-related crashes. State highway safety offices can also promote dissemination of effective practices through the types of safety projects recommended and funded. 

The same cooperative methods can be useful in addressing local speeding or aggressive driving concerns, for example, in a neighborhood or on a road segment or corridor. Public safety, local public works or engineering departments, the State DOT, and potentially other partners including community leaders and concerned people should be involved at an early stage in the speed management process. An interdisciplinary speed management working group may help to foster long-term commitment, cooperation, and improvement over time (Bagdade et al., 2012).

The national Speed Management Program Plan updated the national speed management goals and actions for the U.S. Department of Transportation. This plan emphasizes the importance of comprehensive and cooperative efforts, and outlines the national role in helping States and local agencies reduce speeding-related crashes, injuries and fatalities using the traditional approaches of engineering, enforcement, education and evaluation (NHTSA, FHWA, & FMCSA, 2014). This national plan has several goals and objectives for the DOT related to developing knowledge about the relationships between travel speed and speed limits on crash risk, causes and types of speeding, and developing and testing innovation measures such as variable speed limits combined with automated enforcement and other new technologies. The plan also aims to provide leadership for public policy decision-making, and technical assistance and tools to help agencies develop speed management strategies that meet local needs. The plan promotes the development of data driven models that target enforcement resources where they are most needed to achieve the greatest safety benefits. 

The national efforts to address dangerous speeding and aggressive driving include better understanding of speeding in relation to road designs and environments, and the motivations and choices of drivers. More comprehensive or different types of measures may be needed to address certain types of speeders, including flagrant and repeat offenders, than are generally employed. As part of a comprehensive road safety strategy, the United Kingdom has embarked upon an ambitious research program known as High UnSafe Speed Accident Reduction (HUSSAR) to understand the human, psychological, and emotional factors in speeding and other dangerous driver behaviors so that interventions may better target barriers to speed compliance (Fuller, Bates, et al., 2008; Fuller, Hannigan, et al., 2008; Stradling et al., 2008; and others). These efforts resulted in the implementation of a national speed awareness course in the United Kingdom that speeders can take as an alternative to paying penalties for low-level speeding infractions (Ipsos MORI et al., 2018). More information is provided about this countermeasure in section A.3.2. As already mentioned, several recent U.S. studies have also begun to characterize speeding motivations and attitudes and types of speeding behaviors that may warrant different types of strategies. 

A significant body of research has also emerged in the past few years shedding light on characteristics of angry and aggressive drivers and risk-taking tendencies such as impulsiveness or even genetic predispositions. A few pilot studies have noted glimmers of success in helping some of these drivers achieve better control. As examples, a group in Estonia pilot-tested an intervention with promising results (Paaver et al., 2013). The intervention was provided by trained psychologists and focused on teaching driving students about impulsive personality and information processing styles, different types of impulsivity and how to recognize such tendencies in oneself, and potential situational triggers that may induce subjects to behave impulsively and take risks. The test group had half as many speeding violations over a year following the intervention as a control group of students from the same driving schools. 

Another effort in the United Kingdom developed and trialed an intensive personal intervention to target attitudes, skills, and knowledge relating to crash risk among young men with social and behavioral risk factors and high levels of road traffic collisions (Tapp et al., 2013). The intervention sought to teach “smoothness and control.” The study measured positive and long-lasting impacts among the men who completed the program. One of the challenges, however, was achieving recruitment and completion among this cohort. 

A small study pilot-tested a work-related driver behavior modification program using feedback and goal setting, as well as a social-norming branding (Newman et al., 2014). This trial showed at least short-term improvement in drivers’ compliance with speed limits. These and other research efforts may ultimately lead to changes in education, training, and enforcement interventions that will have more beneficial effects on safety than most driver interventions to date.

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