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Deterrence means enacting laws that prohibit impaired driving, publicizing and enforcing those laws, and punishing offenders. Deterrence works by changing behavior through fear of apprehension and punishment. If drivers believe their impaired driving is likely to be detected and they are likely to be arrested, convicted, and punished, many will not drive impaired by alcohol. This strategy, called general deterrence, influences the general driving public. Examples include well-publicized and highly visible enforcement such as sobriety checkpoints. In contrast, specific deterrence refers to efforts to influence drivers who have been arrested for impaired driving so they will not continue to drive impaired. Examples include ignition interlocks and vehicle sanctions for DWI offenders. Although most of this discussion relates to alcohol-impaired driving, much could be applied to drug-impaired driving as well.

Deterrence works when consequences are swift, sure, and severe (with swift and sure being more important in affecting behavior than severe). All States have basic laws in place to define impaired driving, set illegal per se limits at .08 g/dL BAC (Utah went to .05 g/dL BAC on December 30, 2018), 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. Law enforcement agencies have limited resources and except at checkpoints officers must observe traffic violations or other aberrant behavior before they can stop motorists.
    • Conviction also may be difficult. DWI laws are complicated; the evidence needed to define and demonstrate impairment is complex; and judges or juries may not impose specified penalties if they believe the penalties are too severe.
    • The DWI control system is complex. There are many opportunities for breakdowns in the system that allow impaired drivers to go unaddressed.

DWI control system operations and management. The DWI control system consists of a set of laws together with the enforcement, prosecution, adjudication, and offender monitoring 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 19 specific impaired-driving countermeasures in the deterrence section, in four groups: laws; enforcement; prosecution and adjudication; and offender treatment, monitoring, and supervision. But the overall DWI control system, including its management and leadership, is more important than any individual countermeasure.

Studies have highlighted the key characteristics of efficient and effective DWI control systems

(Hedlund & McCartt, 2002; Robertson & 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 completion of all sentence requirements;
    • adequate resources for staff, facilities, training, equipment, and new technology; and
    • coordination and cooperation in and across all components.

Some countermeasures discussed in this chapter, such as BAC Test Refusal Penalties (Section 1.4), Alcohol-Impaired-Driving Law Review (Section 1.5), and DWI courts (Section 3.1), are directed at improving DWI system operations. In some instances, the most important action that SHSOs can take to reduce alcohol-impaired driving is to review and improve DWI control system operations, perhaps using State DWI task forces and/or State impaired-driving program assessments.

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. Although two decades have passed, the basic findings of the Ulmer group are still applicable. SHSOs should keep this in mind as they consider the specific countermeasures in this chapter.