Evaluation of State Ignition Interlock Programs: Interlock Use Analyses from 28 States, 2006–2011

Casanova-Powell, Tara; Hedlund, James H.; Leaf, William; Tison, Julie · 2015 · ROSA P / United States. National Highway Traffic Safety Administration

archive: archived pipeline: cataloged verified

Get this paper ↗ (full text — opens at the source; we link to it, we don't host it)

Summary

This report evaluates state ignition interlock programs to identify best practices for increasing device usage among driving while intoxicated (DWI) offenders. Motivated by the fact that alcohol-impaired driving accounted for 31% of motor vehicle fatalities in 2012 and that only 21% of DWI arrestees installed interlocks in 2013, the study aimed to determine which program features and policy changes correlate with higher interlock use rates. The research was conducted by the Preusser Research Group on behalf of the Governors Highway Safety Association, in collaboration with the National Highway Traffic Safety Administration (NHTSA) and the Centers for Disease Control and Prevention (CDC). The study analyzed data from 28 states with more than 2,000 interlocks in use in 2010, covering the period from 2006 to 2011. Researchers obtained interlock-in-use counts from Impact DWI, Inc., and state agencies, calculating usage rates per 10,000 population, per 100 DWI arrests, and per DWI fatality. They also assessed eight "program keys" across three categories: Program Design (requirements, penalties), Program Management (monitoring, uniformity, coordination, education), and Program Support (resources, data). States were rated on a 5-point scale for each key based on interviews with program staff and review of laws. Correlation analyses measured the relationship between these ratings and interlock use rates, while trends in usage were compared against specific legislative or administrative changes implemented between 2007 and 2010. The results showed a 183% increase in total interlocks in use across the 28 states from 2006 to 2011. Policy changes expanding requirements to first-time offenders, high-BAC offenders, or those seeking hardship licenses were consistently associated with increased usage. For example, requiring interlocks for first offenders led to increases in all three states that implemented such laws during the study period. Correlation analysis revealed that "Requirements" had the strongest relationship with higher interlock use rates, followed by "Monitoring." Program management keys, including coordination, uniformity, and education, also showed moderate to strong positive correlations. Conversely, the "Data" key showed the weakest correlation with usage rates, though it was identified as critical for supporting other program functions. The study concludes that to maximize interlock usage, states should prioritize strong program design, specifically expanding requirements to cover more offender categories, particularly first-time DWI offenders. These design elements must be supported by robust program management, including careful monitoring and inter-agency coordination. While resources and data systems showed weaker direct correlations with usage rates, they are essential for effective program administration and evaluation. The authors recommend that states improve record-keeping systems to better track offenders and evaluate program effectiveness, noting that current data limitations hinder comprehensive assessment of interlock program success.

Key finding

Interlock program requirements covering more offender categories, especially first-time offenders, and strong program management features like monitoring and coordination are significantly associated with higher ignition interlock usage rates.

Methodology

dataset

Sample size: 28

Provenance

The full processing record for this entry. Every stage of this paper's journey through the pipeline is logged — what ran, with which tool and model, how many attempts it took, and when it last completed. Discovered via bulk_ingest_rosap on 2026-05-23 (6 acquisition events logged).

Summary generated by qwen3.6-27b-prismaquant on 2026-06-10; verification: verified.

Topics

Ranked by relevance to this paper. Hover a topic for its definition.

• alcohol detection systems
• dui enforcement