3. Aggressive Driving and Speeding
Overview
Aggressive driving is generally understood to mean driving actions that markedly exceed the norms of safe driving behavior and that place the driver or other road users in unnecessary danger (NHTSA, 2000; NCHRP, 2003). Aggressive behaviors may be directed at other drivers or pedestrians through actions such as following too closely or erratic and unsafe lane changes. Or aggressive behaviors may violate the established traffic control system through speeding or running red lights. All aggressive driving violates some traffic laws, but not every moving violation is considered aggressive driving. Aggressive driving should not be confused with road rage: an intentional assault by a driver or passenger, with a motor vehicle or a weapon, on the roadway or precipitated by an incident on the roadway.
The legal definition of speeding is exceeding the posted speed limit. In practice, law enforcement officers seldom write citations for speeds less than 5 or sometimes 10 mph over the posted limit (GHSA, 2005). Speeding becomes aggressive driving when a vehicle's speed is too high for conditions or substantially exceeds the prevailing travel speeds of other vehicles.
Problem size. Speeding is common, and on some roads almost universal. About two-thirds of all drivers in NHTSA's 2002 national survey reported that they exceeded the posted speed limit on each type of road -- interstate, non-interstate multilane, two lane, and city streets -- within the past week, and about one-third reported this behavior on the day of the interview (Royal, 2004, p. 29). One-third of all drivers reported that they often or sometimes drive at least 10 mph faster than most other vehicles (Royal, 2004, p. 31). Yet two-thirds of drivers felt that other speeding drivers pose a major threat to their personal safety (Royal, 2004, p. 43; NHTSA, 2003a). NHTSA estimated that speeding, as determined by the investigating officer, was a contributing factor in 31 percent of fatal crashes in 2003 (NHTSA, 2004a) and 2004 (NHTSA, 2005b, slide 39). In-depth investigations found speeding to be a causal factor in 19 percent of a sample of serious crashes in 1996-1997 (Hendricks et al., 2001a; Hendricks et al., 2001b).
Speeding can be dangerous on all roads. In 2003, half of the speed-related traffic fatalities occurred on roads posted at 50 mph or less and one-quarter occurred on roads posted at 35 mph or less (NHTSA, 2005a, Table 118).
Aggressive driving actions other than speeding also are common, though they are more difficult to measure accurately. In NHTSA's survey, 40 percent of drivers reported that they sometimes or often enter an intersection "just as the light turned from yellow to red," which is a good working definition of red light running. In the same survey, 10 percent reported sometimes or often cutting in front of another driver (Royal, 2004, p. 47; NHTSA, 2003a). About one-third of drivers reported that they feel threatened by other drivers at least several times monthly (Royal, 2004, p. 59). NHTSA 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, 2001a).
Strategies to Reduce Aggressive Driving and Speeding
Aggressive driving, speeding, and red-light running all 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 safety belt nonuse: highly publicized and highly visible enforcement of practical, sound, and broadly accepted laws. In particular, speed limits should be set carefully and rationally, taking into account the road segment's design speed, traffic operations, and environmental conditions; if not, many drivers will exceed the speed limit. Enforcement can be conducted through regular traffic patrols; short, intense, highly publicized enforcement periods; or automated speed or red-light enforcement. The sections in this chapter discuss the relevant laws and sanctions, enforcement techniques, and publicity needs. General communications and outreach campaigns urging tolerant and nonaggressive driving behavior also have been used in an attempt to reduce aggressive driving and speeding.
Environmental and vehicular measures also can be effective. As examples, traffic calming measures can reduce speeds, especially on local roads (TRB, 1998, p. 13). Well-coordinated traffic signals can improve traffic flow and reduce red-light running. Adequately designed turn bays and entrance and exit ramps can reduce improper merging and driving on the shoulder (NCHRP, 2003, Strategy B1). A variety of measures to reduce congestion can diminish driver frustration that leads to aggressive driving ( Shinar and Compton , 2004). Company policies, backed up with speed monitors and logs or even speed regulators, can reduce commercial vehicle speeding. These environmental and vehicular strategies are not included in this guide because SHSOs have little or no direct authority or responsibility for them. However, managing traffic operations in general and speeds in particular requires cooperative efforts between State DOTs and SHSOs. SHSOs are encouraged to act cooperatively with State DOTs to identify their aggressive driving and speeding problems and to adopt comprehensive plans and programs to address them. See NCHRP (2003) for examples of cooperative strategies.
The same cooperative methods can be useful in addressing local aggressive driving or speeding concerns, for example in a neighborhood or on a road segment or corridor. Working together, State and community traffic engineers, law enforcement, safety officials, community leaders, and concerned citizens can develop comprehensive plans and programs.
The Department of Transportation's 2005 Speed Management Strategic Initiative (U.S. DOT, 2005) contains a comprehensive set of engineering, enforcement, and education strategies to reduce speeding-related fatalities, injuries, and crashes. The Department, together with GHSA and several national organizations, sponsored a National Forum on Speeding in June 2005. The forum's goals were to identify effective strategies to reduce speeding-related crashes; coordinate Federal, State, local, and private sector speeding-related policies and programs; and identify additional needed data and research. The forum report will be released in 2005.
Countermeasures That Work
Countermeasures to reduce aggressive driving and speeding are listed below and discussed individually in this chapter. The table is intended to give a rough estimate of each countermeasure's effectiveness, use, cost, and time required for implementation. The terms used are described below. Effectiveness, cost, and time to implement can vary substantially from State to State and community to community. Costs for many countermeasures are difficult to measure, so the summary terms are very approximate. See each countermeasure discussion for more information.
1. Laws
Proven* |
High |
Low |
Short |
Unknown |
Low |
Low |
Short |
* When enforced and obeyed
2. Enforcement
Uncertain |
Low |
High |
Medium |
Proven |
Medium |
High* |
Medium |
Varies |
Unknown |
Varies |
Varies |
*Can be covered by income from citations
3. Penalties and Adjudication
Proven |
High |
Varies |
Low |
Unknown |
Unknown |
Varies |
Varies |
4. Communications and Outreach
Likely |
Medium |
Varies |
Medium |
Effectiveness:
Proven: demonstrated by several high-quality evaluations with consistent results.
Likely: balance of evidence from high-quality evaluations.
Uncertain: limited and perhaps ambiguous evidence.
Unknown: no high-quality evaluation evidence.
Varies: different methods of implementing this countermeasure produce different results.
Effectiveness is measured by reductions in crashes or injuries unless noted otherwise.
See individual countermeasure descriptions for information on effectiveness size and how effectiveness is measured.
Use:
High: more than two-thirds of the States, or a substantial majority of communities.
Medium: between one-third and two-thirds of States or communities.
Low: fewer than one-third of the States or communities.
Unknown: data not available.
Cost to implement:
High: requires extensive new facilities, staff, or equipment, or makes heavy demands on current resources.
Medium: requires some additional staff time, equipment, and/or facilities.
Low: can be implemented with current staff, perhaps with training; limited costs for equipment or facilities.
Time to implement:
Long: more than one year.
Medium: more than three months but less than one year.
Short: three months or less.
These estimates do not include the time required to enact legislation or establish policies.