Prize-based contingency management: A vehicle miles of travel reduction intervention

Abstract

During the past 50 years, air pollution has become a growing problem throughout the Intermountain West because of increases in personal vehicle ownership and usage.Scientists continue to design interventions to improve air quality by encouraging people to reduce their personal vehicle miles of travel (VMT). However, results of these interventions have only seen modest reductions in VMT because of some methodological and measurement issues. To address these limitations, a 14-week driving reduction intervention was conducted in Cache County, Utah. This intervention employed a prizebased contingency management system within a single-subject, A-B-A withdrawal research design that rewarded participants with prizes if they were able to reduce their VMT below their baseline mean. The VMT was measured each day with an in-car GPS electronic tracking device. Results of this intervention indicate both short-and long-term reductions in VMT as a result of the treatment. Specifically, 6 of the 10 participants iv showed a statistically significant reduction from the baseline to the intervention stage and maintenance of this reduction during the return-to-baseline stage. The other four participants exhibited a similar pattern but their change in vehicle miles of travel was not statistically significant. Interaction effects were not found between the "Choose Clean Air" social marketing campaign, gas prices, temperature, and PM 2.5 levels. Despite some problems with the transmission and recording of VMT data, this intervention provides further evidence for the application of prize-based contingency management systems to the reduction of a problematic behavior or encouragement of proenvironmental or pro-social behaviors. The in-car GPS devices improved VMT data collection and quality of the data but hardware and software improvements are still needed to prevent data loss. Further replication is necessary to determine the efficacy of driving reduction intervention that employs prize-based contingency management systems at the community or group level. Future research should also test the possible demographic differences between those that respond favorably to this type of intervention and those that do not, and the differences between prize delivery systems (immediate versus delayed) and prize magnitude (low-versus high-dollar amounts) on driving behaviors.(164 pages) v ACKNOWLEDGMENTS