1. Alcohol-Impaired Driving

Overview

Alcohol-impaired drivers were involved in about one-quarter of U. S. traffic fatalities in 2003 (NHTSA, 2004d; NHTSA, 2005a, Table 19):

• 14,260 alcohol-involved drivers in fatal crashes (25% of all drivers in fatal crashes);
  
  
• 11,996 drivers in fatal crashes with a BAC over .08 grams per deciliter (21% of all drivers in fatal crashes).

Early estimates suggest that the number of alcohol-involved drivers decreased slightly in 2004, to 13,952 (NHTSA, 2005b, slide 27). See NHTSA’s most recent Traffic Safety Facts (NHTSA, 2005a) and State Alcohol Estimates (NHTSA, 2004d) for the latest national and State data.

Trends. Alcohol-impaired driving dropped steadily from 1982 to the mid-1990s for many reasons. Substantial public attention, the growth of grassroots organizations such as MADD and RID, increased Federal funding, State task forces, tougher laws, increased enforcement, and intensive publicity all combined to help address this critical traffic safety problem.

Unfortunately, as the chart shows, impaired driving levels have changed very little since 1992. The easy gains have been made. Public attention and government resources have been redirected to other social problems.

Source: FARS

Drinking and driving characteristics (Hedlund and McCartt, 2002). Drinking and driving is common, with at least 80 million trips made annually by drivers who are over .08 BAC. Arrests are rare, with less than one arrest for every 50 trips by a driver over .08 BAC.

Many drinking drivers are “high risk,” with one or more of the following characteristics:

• Half of drinking drivers in crashes or arrests have a BAC of .15 or higher.
  
  
• One-third of drinking drivers in crashes or arrests have a prior DWI conviction.
  
  
• One-quarter of drinking drivers in surveys have some indication of an alcohol problem.

Alcohol-impaired driving is affected by several external factors, including geography, urbanization, road structure and conditions, and economic activity, as well as by a State’s laws and programs. For all of these reasons, both the current level of alcohol-impaired driving and the progress in reducing alcohol-impaired driving vary greatly from State to State. For example, comparing all 50 States and the District of Columbia (NHTSA, 2004d):

• the proportion of drivers in fatal crashes with a BAC of .08 or more in 2003 ranged from 8 percent in the lowest State to 31 percent in the highest.
  
  
• The change in traffic fatalities involving any alcohol from 1982 to 2003 ranged from a decrease of 63 percent in the best State to an increase of 11 percent in the worst.

Strategies to Reduce Alcohol-Impaired Driving

Five basic strategies are used to reduce alcohol-impaired driving crashes and consequences:

• Deterrence: enact, publicize, enforce, and adjudicate laws prohibiting alcohol-impaired driving;
  
  
• Prevention and intervention: reduce drinking, keep drinkers from driving;
  
  
• Communications and outreach: inform the public of the dangers of impaired driving and establish positive social norms that make driving while impaired unacceptable;
  
  
• Alcohol treatment: reduce alcohol dependency or addiction among drivers;
  
  
• Other traffic safety measures: implement strategies that affect alcohol-impaired drivers and other drivers as well.

This chapter includes countermeasures for the first four strategies. Deterrence countermeasures are divided into four sections: (1) laws, (2) enforcement, (3) prosecution and adjudication, and (4) offender treatment, monitoring, and control. Alcohol treatment is included in the offender section. Prevention, intervention, communications, and outreach countermeasures are combined in a single section. The Underage Drinking and Alcohol-Related Driving section includes deterrence, prevention, and communications measures specific to this age group.

Many other traffic safety countermeasures help reduce alcohol-related crashes and casualties but are not discussed in this chapter. Behavioral countermeasures, such as those that increase safety belt use and reduce speeding, are discussed in other chapters. Vehicle and environmental countermeasures, such as improved vehicle structures and centerline rumble strips, are not included because SHSOs have little or no authority or responsibility for them. See the series of NCHRP Report 500 guides for the AASHTO Strategic Highway Safety Plan, especially the impaired driving guide (NCHRP, under review), for detailed discussions of environmental measures.

Key terms BAC: Blood alcohol concentration in the body, expressed as grams of alcohol per deciliter (g/dL) of blood, usually measured with a breath or blood test. DWI: the offense of driving while impaired by alcohol. In different States the offense may be called Driving While Intoxicated, Driving Under the Influence (DUI), or other similar terms. MADD: Mothers Against Drunk Driving. PAS: Passive Alcohol Sensor, a device to detect alcohol presence in the air near a driver’s face, used to estimate whether the driver has been drinking. PBT: Preliminary Breath Test device, a small handheld alcohol sensor used to estimate or measure a driver’s BAC. RID: Remove Intoxicated Drivers SFST: Standardized Field Sobriety Tests, a battery of three simple performance tasks (One-Leg Stand, Walk-and-Turn, and Horizontal Gaze Nystagmus) used by law enforcement at the roadside to estimate whether a driver is impaired by alcohol. Illegal per se law: A law that makes it an offense in and of itself to operate a motor vehicle with a BAC at or above a specified level.

Countermeasures That Work

Countermeasures to reduce alcohol-impaired driving are listed below and discussed individually in the remainder of 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. Deterrence: laws

Countermeasure	Effectiveness	Use	Cost	Time
1.1 ALR/ALS	Proven	High	High	Medium
1.2 BAC test refusal penalties	Proven-refusals	Unknown	Low	Short
1.3 High-BAC sanctions	Uncertain	Medium	Low	Short
1.4 Open containers	Uncertain	High	Low	Short
1.5 DWI code review	Likely	Low	Medium	Medium

2. Deterrence: enforcement

Countermeasure	Effectiveness	Use	Cost	Time
2.1 Sobriety checkpoints	Proven	Medium	High	Short
2.2 Saturation patrols	Proven-arrests	High	Medium	Short
2.3 Integrated enforcement	Likely	Unknown	Low	Short
2.4 Preliminary Breath Test Devices	Proven- arrests	High	Medium	Short
2.5 Passive sensors	Proven-arrests	Unknown	Medium	Short

3. Deterrence: prosecution and adjudication

Countermeasure	Effectiveness	Use	Cost	Time
3.1 Sanctions	Varies	Varies	Varies	Varies
3.2 Diversion, plea agreement restrictions	Proven-convictions	Medium	Low	Short
3.3 DWI courts	Likely	Low	High	Medium
3.4 Court monitoring	Proven-convictions	Unknown	Low	Short

4. Deterrence: DWI offender treatment, monitoring, and control

Countermeasure	Effectiveness	Use	Cost	Time
4.1 Alcohol problem assessment, treatment	Proven	High	Varies	Varies
4.2 DWI offender monitoring	Proven-recidivism	Unknown	High	Medium
4.3 Alcohol interlocks	Proven	Medium	Medium	Medium
4.4 Vehicle and license plate sanctions	Varies	Medium	Varies	Medium
4.5 Lower BAC limit for repeat offenders	Uncertain	Low	Low	Short

5. Prevention, intervention, communications and outreach

Countermeasure	Effectiveness	Use	Cost	Time
5.1 Responsible beverage service	Likely	Medium	Medium	Medium
5.2 Alternative transportation	Unknown	Unknown	Medium	Short
5.3 Designated drivers	Unknown	Medium	Low	Short
5.4 Alcohol screening and brief interventions	Proven	Medium	Medium	Short
5.5 Mass-media campaigns	Proven *	High	High	Medium

6. Underage drinking and alcohol-related driving

Countermeasure	Effectiveness	Use	Cost	Time
6.1 Age 21 enforcement	Varies	Varies	Varies	Varies
6.2 Zero-tolerance enforcement	Likely	Unknown	Medium	Short
6.3 School education programs	Uncertain	Unknown	Low	Long
6.4 Youth programs	Uncertain	High	Varies	Medium

Effectiveness:

Proven: demonstrated by several high-quality evaluations with consistent results
Likely: balance of evidence from high-quality evaluations or other sources
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: less than one-third of the States or communities
Unknown: data not available

Cost to implement:

High: requires extensive new facilities, staff, equipment, or publicity, or makes heavy
demands on current resources
Medium: requires some additional staff time, equipment, facilities, and/or publicity
Low: can be implemented with current staff, perhaps with training; limited costs for
equipment, facilities, and publicity

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.

Deterrence

Deterrence means enacting laws that prohibit driving while impaired, publicizing and enforcing those laws, and punishing the offenders. Deterrence works by changing behavior through the fear of punishment. If drivers believe that impaired driving is likely to be detected and that impaired drivers are likely to be arrested, convicted, and punished, many will not drive while impaired by alcohol. This strategy is sometimes called general deterrence because it influences the general driving public through well publicized and highly visible enforcement activities and subsequent punishment. In contrast, specific deterrence refers to efforts to influence drivers who have been arrested for impaired driving so that they will not continue to drive while impaired by alcohol.

Deterrence works when consequences are swift, sure, and severe (with swift and sure being more important in affecting behavior than severe). All States have the basic laws in place to define impaired driving, set illegal per se limits at .08 BAC, and provide standard penalties.

Deterrence, however, is far from straightforward, and complexities can limit the success of deterrence measures. For instance:

• Detecting alcohol-impaired drivers is difficult. Alcohol-impaired driving is a common behavior, law enforcement agencies have limited resources, and (except at checkpoints) officers must observe some traffic violation or other aberrant behavior before they can stop a motorist.
  
  
• Conviction also may be difficult. DWI laws are extremely complicated (20 pages in some State codes); the evidence needed to define and demonstrate impairment is complex; judges and juries may not impose specified penalties for an action that they do not believe is a “real crime.”
  
  
• The DWI control system is complex. There are many opportunities for breakdowns in the system that allow impaired drivers to go unpunished.

DWI control system operations and management.

The DWI control system consists of a set of laws together with the enforcement, prosecution, adjudication, and offender follow-up policies and programs to support the laws. In this complicated system, the operations of each component affect all the other components. Each new policy, law, or program affects operations throughout the system, often in ways that are not anticipated.

This guide documents 16 specific impaired driving countermeasures in the deterrence section, in four groups: laws, enforcement, prosecution and adjudication, and offender treatment, monitoring, and control. But the overall DWI control system, including its management and leadership, is more important than any individual countermeasure.

Recent studies have highlighted the key characteristics of an efficient and effective DWI control system (Hedlund and McCartt, 2002; Robertson and Simpson, 2003):

• Training and education for law enforcement, prosecutors, judges, and probation officers;
  
  
• record systems that are accurate, up-to-date, easily accessible, and able to track each DWI offender from arrest through the completion of all sentence requirements;
  
  
• adequate resources for staff, facilities, training, equipment, and new technology; and
  
  
• coordination and cooperation within and across all components.

A few of the countermeasures discussed in this guide, such as BAC test refusal penalties (Chapter 1, Section 1.2), DWI code review (1.5), and DWI courts (3.2), are directed at improving DWI system operations. Most, though, are not. The most important action many SHSOs can take to reduce alcohol-impaired driving may be to review and improve DWI control system operations, perhaps using a State DWI task force and/or a State alcohol program assessment.

Ulmer et al. (1999) investigated why some States reduced alcohol-related traffic fatalities more than others. They concluded that there is no “silver bullet,” no single critical law, enforcement practice, or communications strategy. Once a State has effective laws, high-visibility enforcement, and substantial communications and outreach to support them, the critical factors are strong leadership, commitment to reducing impaired driving, and adequate funding. SHSOs should keep this in mind as they consider the specific countermeasures in this chapter.