MC Helmet

V. EFFECTS OF HELMET LAW CHANGES IN ARKANSAS,
KENTUCKY, LOUISIANA AND TEXAS

As noted earlier, Arkansas, Kentucky, Louisiana, and Texas repealed all-rider motorcycle helmet laws in the late 1990's. Evaluations of the near term effects of these law changes can be found in Preusser et al., (2000) and Ulmer et al., (2003). Since those studies, additional years of fatality data have become available in FARS and are examined here.

Table 13 and Figure 16 show the annual numbers of motorcyclists killed in these States during the 1994-2003 period.

Table 13. Motorcyclists Killed in Arkansas, Kentucky, Louisiana, and Texas, 1994-2003
Year	Arkansas	Kentucky	Louisiana	Texas
1994	24	32	28	124
1995	14	19	28	124
1996	24	24	28	110
1997	18	24	19	112
1998	28	27	34	147
1999	21	40	40	174
2000	27	36	57	222
2001	37	57	63	234
2002	37	43	66	244
2003	54	54	74	313

Source: FARS Grayed year is the year of law change. [presume that's the indication?]

These data indicate that motorcyclist fatalities increased in all 4 States following repeal of their all-rider helmet laws. Comparing the 3 full years following the law changes with the 3 full years prior to the changes indicates a 130 percent increase in Louisiana, a 99 percent increase in Kentucky, a 52 percent increase in Texas, and a 23 percent increase in Arkansas.

Time Series Analyses

ARIMA modeling was also conducted for these States. As with Florida, the analyses explored monthly fatalities over a 9 year period (1994-2002) in the presence of the annual number of motorcycles registered in each State. Table 13 presents the results.

Table 14 indicates that Arkansas was the only law change State that failed to show a statistically significant change in the rate of motorcycle fatalities following the change in law. As noted, fatalities increased in Arkansas following its law change but by the smallest percentage of all of the States considered. Also, the small numbers of monthly fatalities does not make the series well suited to time series analysis.

Figure 16. Arkansas, Kentucky, Louisiana, and Texas Motorcyclist Fatalities, 1994-2003

Table 14. Arkansas, Kentucky, Louisiana, and Texas Interrupted Time Series Results
State	Repeal Date	Months Pre/Post	Months Pre/Post	Significant Component	B	T- Ratio	Approx. p
Arkansas	(0,0,0) (0,1,1)	Aug 1997	43/65	-	-	-	-
Kentucky	(0,0,0) (1,0,1)	Jul 1998	54/54	Intervention	1.31	3.32	<.001
Louisiana	(0,0,0) (0,0,0)	Aug 1999	67/41	Intervention	2.64	6.67	<.001
Texas	(0,0,0) (1,0,1)	Sep 1997	44/64	Intervention Registrations	3.71 1.0x10⁴	3.41 5.08	<.001 <.001

* All models produce PACF and ACF values that are not statistically significant.

For Kentucky, there was a statistically significant effect of the intervention on fatalities such that there was an average increase of 1.3 motorcycle fatalities per month ( p = .001). Registrations did not enter the model as a statistically significant parameter.

Louisiana also showed a significant effect of intervention. For this State, the repeal of the law raised motorcycle fatalities by an average of 2.6 per month ( p < .001). There was no statistically significant effect of registrations on fatalities.

Texas's results demonstrated statistically significant effects of both intervention (fatalities increasing an average of 3.7 per month; p = .001) and registrations (fatalities increasing by 1 as registrations increase by 10,000, p < .001) on the number of motorcycle fatalities. That is, while there was an effect of registrations on a change in the rate of fatalities, there was also a separate effect of the law repeal.

Index

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