Impact of seat belt use on driving behavior

Economic Inquiry, Oct, 1992 by Harinder Singh, Mark Thayer

Finally, the Years of Seat Belt Use variable is negative and significantly different from zero. Thus, the number of moving violations declines in all groups the longer one wears a seat belt. This is an indication of learning, which results in less compensating behavior over time.

TABLE III
Impact of Seat Belt Use on Number of Tickets Pooled Estimates
Explanatory
Variables                    Coefficients   t-statistics
Risk Lover Group                -.005           -.017
Risk Lover*Seat Belt Use         .327           4.28
Risk Neutral Group               .487           1.64
Risk Neutral*Seat Belt Use       .136           1.62
Risk Averse Group               3.68            2.23
Risk Averse*Seat Belt Use       -.935          -1.69
Years of Seat Belt Use          -.011          -3.65
Education                        .0003           .02
Income                           .007            .40
Sex                              .048            .83
Age                             -.011          -3.78
Distance to Work                -.0005          -.57
Underage Children                .012            .47
R-Square                         .08
Number of Observations           690

In Table IV an alternative empirical specification is presented. We performed an F-test to determine the efficacy of including the three groups, distinguished by the risk index, in a single equation. The F-statistic for the unrestricted specification (three separate equations) compared to the restricted specification (single equation) is 2.20 versus the critical value of 2.10 (at 1 percent level). This implies that the three equations may be analytically distinct. Thus, in Table IV we present three separate estimated equations.

As in the previous pooled model all results are reported with White's heteroscedastic correction. The test statistics for the three equations (risk lovers, risk neutral, risk averse) are 2.16, 2.49, and 2.47, respectively. All exceed the 5 percent significance level, indicating that White's correction is needed.

As is illustrated, the overall significance of the individual regressions for the risk lover and risk averse groups are markedly improved. However, the conclusions drawn above for the single-equation model generally remain in effect. The control variables continue to perform poorly. Moreover, the pattern for Seat Belt Use and Years Wearing Seat Belt remains the same. The risk lover group demonstrates strong compensating behavior whereas the risk TABULAR DATA OMITTED averse group does not compensate. Learning (illustrated by the Years of Seat Belt Use variable) continues to be significantly different from zero for the risk neutral and risk averse groups. However, this variable is not significant among the risk lover group, implying that this group shows minimal learning. Thus, compensating behavior is not offset over time in this group.

Since the control variables do not perform as expected, we eliminated them as a final test of the stability of the estimated coefficients. Our conclusions regarding Seat Belt Use and Years Wearing Seat Belt are unchanged. The estimated coefficients (t-statistics in parentheses) on Seat Belt Use were .29 (3.71), .10 (1.22), and -.89 (-1.61) for the three groups (risk lovers, risk neutral, risk averse), respectively. In addition, the pattern of learning established above remains the same.