Fredrick M. Streff

ARE THERE REALLY SHORTCUTS? ESTIMATING SEAT BELT USE WITH SELF-REPORT MEASURES

We examined the utility of estimating rates of automobile seat belt use with self-report measures. Self-report measures overestimate belt use rates compared to observational surveys of the same population. Laws mandating seat belt use did not substantially affect the degree to which self-reports are upwardly biased. We found self-report measures overestimate observed belt use by 8.9 to 19.4 percentage points or by a factor of 1.2 to 2. Our best estimate is that self-reported seat belt use rates be discounted by 12 percentage points to estimate actual belt use rates.

An experimental test of risk compensation: Between-subject versus within-subject analyses

This study examined parameters under which risk compensation in driving can occur following the use of safety belts. Risk compensation theories hypothesize that if individuals use safety belts, they will drive in a more risky manner than if they do not use safety belts due to an increased perception of safety. Although the existence of risk compensation in driving has been debated in the literature for many years, the current study was the first experimental analysis of this theory that permitted a controlled examination of both between-subject and within-subject effects. This study required subjects to drive a 5-hp. go-kart around an oval track either buckled or unbuckled in the first of two phases of 15 driving trials. After the first phase the safety condition was switched for half the subjects (i.e., the safety belt was removed from subjects using it or was used by subjects who previously did not use it). Dependent measures included latency for each lap, deviations from the prescribed lane, and perceived safety while driving. The amount of time it took for subjects to travel to the go-kart track and their safety belt use during that trip was also measured. Risk compensation theory was not supported in the between-subject analyses of the research data; however, some within-subject comparisons did demonstrate risk compensation. Subjects who switched from not using the safety belt to using it increased driving speed during the second phase significantly more than subjects who used the safety belt during both driving phases. The study suggested that the occurrence of risk compensation is dependent upon individuals being able to compare the sensations using a safety belt with those of not using a safety belt. Risk compensation did not manifest itself in between-subject studies because this comparison could not take place. The implications of this study to driving automobiles on multi-user roadways is discussed. Suggestions for research to further expand the knowledge about how and when risk compensation occurs are also provided.

PUBLIC OPINION ON ALCOHOL POLICIES

We conducted a survey of a probability sample of adult residents in the State of Michigan, assessed public support for various alcohol and drinking-driving policy changes, examined how opinions on various policies clustered, and compared Michigan results with national surveys on these issues. Results showed high levels of public support for raising alcohol excise taxes (82 %), prohibiting concurrent sales of alcohol and gasoline (74 %), administratively suspending drivers licenses of those over the legal alcohol limit (67 %), limiting the numbers of alcohol outlets via government regulation (63 %), and lowering the legal alcohol limit for drivers to .05 g/dl (55 %). Support for these policies was found across all income and education categories, but was significantly lower among frequent heavy drinkers. Policies with lower levels of public support include liability of commercial servers and social hosts, and stricter limits on hours of alcohol sales. Results are clearly relevant to current policy debates, and point to the need for further research on how opinions concerning alcohol policies are interrelated.

REDUCTIONS IN POLICE-REPORTED INJURIES ASSOCIATED WITH MICHIGAN'S SAFETY BELT LAW

This research measured the effects of Michigans compulsory safety belt use law on traffic crashes and injuries of various severities. Using time-series methods, the authors analyzed monthly frequencies of crash-induced injuries and fatalities from January 1978 through December 1987. Exposure to risk of occupant injury was controlled statistically by including aggregate frequency of crashes as a covariate in time-series models. Effects of economic conditions on traffic crashes were controlled by including an index of unemployment as a covariate. The following statistically significant effects were associated with the safety belt law: (a) In crashes with minor vehicle damage, there was a 14.6% reduction in B-level injuries, an 11.0% reduction in C-level injuries, and a 13.0% reduction in aggregate (KABC) injuries; (b) in crashes with moderate vehicle damage, there was a 16.8% reduction in A-level injuries, an 11.6% reduction in B-level injuries, a 10.7% reduction in C-level injuries, and a 3.6% reduction in aggregate (KABC) injuries; (c) in crashes with severe vehicle damage, there was a 6.3% reduction in fatalities, an 11.8% reduction in B-level injuries, a 4.7% reduction in c-level injuries, and a 5.8% reduction in aggregate (KABC) injuries; (d) for all vehicle damage severities, there was a 14.0% reduction in B-level injuries, an 8.3% reduction in C-level injuries, and a 6.4% reduction in injuries to front-seat occupants. Based on these results, Michigans adult safety belt law has prevented 31,710 injuries from July 1985 through December 1988.

Use of automatic safety belts in Michigan

The use of automatic safety belts among motorists throughout the state of Michigan was examined in May 1990 as part of a broader direct-observation survey to measure compliance with Michigans mandatory safety belt use law. Use of the two most common types of automatic belt systems were measured: the nonmotorized detachable three-point lap and shoulder belt system and the motorized shoulder belt with manual lap belt system. A total of 828 drivers and 237 front-right passengers were observed with automatic belt systems between April 30, 1990 and May 24, 1990. Use of nonmotorized detachable three-point lap and shoulder belt systems was 74.3%. Lap belt use of motorized shoulder and manual lap belt systems was 79.2%. Of all motorized shoulder belt and manual lap belt systems observed, 97.4% had the shoulder belts connected.

Increasing safety belt use in a secondary enforcement state: evaluation of a three-county special enforcement program.

Special enforcement programs to increase belt use present a unique challenge in states with secondary enforcement laws. This paper reports findings from an evaluation of a combined public information and education/enforcement program to increase restraint use along a highly traveled corridor in three Michigan counties. This program (US-31 SAVE) was successful in increasing belt use at least temporarily along the special enforcement corridor. Observed belt use increased from a baseline rate of 56.7% to 65.1% during the program before slipping slightly to 62.7% after the intensive enforcement and PI&E declined (all differences significant at p less than .05). This paper details program and evaluation activities and suggests future research needs to better understand the most effective mix of public information and enforcement efforts in states with secondary belt use laws.

Estimating Costs of Traffic Crashes and Crime: Tools for Informed Decision Making

Traffic crashes and crime both impose significant economic and social burdens through injury and loss of life, as well as property damage and loss. Efforts to reduce crashes and crime often result in competing demands on limited public resources. Comparable and up-to-date cost data on crashes and crime contribute to informed decisions about allocation of these resources in important ways. As a first step, cost data provide information about the magnitude of the problems of crashes and crime by allowing us to estimate associated dollar losses to society. More importantly, cost data on crashes and crime are essential to evaluating costs and benefits of various policy alternatives that compete for resources.This paper presents the first comparable comprehensive cost estimates for crashes and crime and applies them to crash and crime incidence data for Michigan to generate dollar losses for the state. An example illustrates how cost estimates can be used to evaluate costs and benefits of crash-reduction and crime-reduction policies in making resource allocation decisions. Traffic crash and selected index crime incidence data from the calendar year 1988 were obtained from the Michigan State Police. Costs for crashes and index crimes were generated and applied to incidence data to estimate dollar losses from crashes and index crimes for the state of Michigan. In 1988, index crimes in Michigan resulted in

Field effectiveness of two restraint systems: The 3-point manual belt versus the 2-point motorized-shoulder/ manual lap belt

0.8 billion in monetary costs and

Automatic safety belt use in Michigan: A two-year follow-up

2.4 billion in total monetary and nonmonetary quality-of-life costs (using the willingness-to-pay approach). Traffic crashes in Michigan resulted in

A COMPARISON OF TWO DIRECT-OBSERVATION METHODS FOR MEASURING DAYTIME SAFETY BELT USE

2.3 billion in monetary costs and