Seat Belt Use on Interstate Highways JoANN K. WELLS, BA, ALLAN F. WILLIAMS, PHD, ADRIAN K. LUND, PHD Abstract: More than 5,000 miles of limited-access highways in the eastern United States and Canada were traveled to observe seat belt use. Overall belt use was 58 percent in the United States and 79 percent in Canada. The data indicate that belt use in the United States follows a different pattern on interstate highways than on other streets and roads, with relatively high belt use rates (over 50 percent) appearing to be somewhat independent of belt use law provisions.
(Am J Public Health 1990; 80:740-742.)
Introduction Information on seat belt use is typically based on observations of motorists on city streets. For example, the National Highway Traffic Safety Administration (NHTSA) has surveyed belt use in 19 major cities annually since 1975.' However, belt use is known to vary according to where observations are made, and one location where belt use typically is higher than on city streets is interstate highways. In surveys in four states, belt use was 10-20 percentage points higher on interstate highways connecting the cities than in the cities.2 Systematic information on seat belt use in vehicles traveling outside cities is lacking. In the four-state study it was collected incidentally as observation teams traveled between cities.2 The present study provides information on belt use on interstate highways in the eastern United States and compares use rates in states and Canadian provinces with and without belt use laws. Methods Seat belt use observations were made by trained observers sitting behind the driver of a passenger van that traveled slower than the prevailing traffic in the far right lane. From that location, observers could clearly see shoulder belt use of front seat occupants of cars, light trucks, and vans passing in the adjacent lane. Lap belt use was not observed. Most cars on the road (all vehicles beginning with model year 1974) have integral lap/shoulder belts in the driver and right front seating positions. However, pre-1974 cars were not excluded so belt use is slightly underestimated. Belt use observations were made on 5,129 miles of interstate highways in 21 eastern states and on limited-access highways in two eastern Canadian provinces from 9 am to 4 pm weekdays in August 1988. Appendix I provides information on thejurisdictions and highways surveyed and belt use law status. It should be noted that the kinds of travel on these highways can vary tremendously from state to state. For example, in New York state, 1-95 is entirely urban with short distances between access points and large volumes of local traffic; in South Carolina the same interstate is entirely rural with relatively long distances between access points. From the Insurance Institute for Highway Safety. Address reprint requests to JoAnn K. Wells, Insurance Institute for Highway Safety, 1005 N. Glebe Road, Arlington, VA 22201. This paper, submitted to the Journal July 14, 1989, was revised and accepted for publication October 3, 1989. C 1990 American Journal of Public Health
AJPH June 1990, Vol. 80, No. 6
Observed differences in belt use for different populations were tested by x2 test of independence; only differences a = 0.05 are reported. Results Seat belt use by the 14,354 front seat occupants observed on the highways surveyed averaged 58 percent in the United States and 79 percent in Canada. Belt use ranged from 48 percent to 66 percent in the 21 states and was 76 percent in Ontario and 84 percent in Quebec (Table 1). In the United States use was higher in states with laws (60 percent) than states without laws (56 percent), but the range of use rates for states with and without laws overlapped considerably. There was no significant difference in belt use between states with laws permitting primary and secondary enforcement. The majority of occupants (57 percent) were in vehicles registered in the state or province in which they were observed. Of those traveling in out-of-state vehicles, motorists from jurisdictions with seat belt laws were more likely to use belts than motorists from non-law jurisdictions, whether observed in states with laws (66 vs 57 percent), provinces with laws (81 vs 74 percent), or non-law states (66 vs 56 percent). Belt use was higher among drivers; in cars, utility vehicles, and passenger vans; among those estimated to be age 25 or older; and among women (Table 2). Discussion Belt use on interstates is higher than belt use in cities in the same state. Even in states without laws, belt use on interstates was greater than 50 percent, about 20 percentage TABLE
1-Intwstaft Boft Use, by Jurisdiction Belt Use
Jurisdiction United States Law Connecficut Florida Illinois Indiana Maryland Michigan New Jersey New York North Carolina Ohio Pennsylvania Tennessee Virginia No Law Delaware
Georgia Kentucky Maine Massachusetts New Hampshire Rhode Island South Carolina Canada Ontario
Quebec
%
(N)
60 58 56 55 58 66 59 65 54 59 64 66 51 63 56 64 59 64 52 49 54 48 60
(7,943) (526) (2,149) (257) (311) (697) (581) (477) (98) (490) (453) (605) (476) (823) (3,311) (59)
76 84
(2,042) (1,058)
(1,265) (140) (711) (404) (63) (212)
(457)
Standard Error of Percent Belt Use 0.6 2.2 1.1 3.1 2.8 1.8 2.0 2.2 5.0 2.2 2.3 1.9 2.3 1.7 0.9 6.2 1.4 4.1 1.9 2.5 6.3 3.4 2.3 0.9 1.1
009040036/90$1.50 741
PUBLIC HEALTH BRIEFS TABLE 2-Interstate Seat Belt Use by Front Seat Occupants by Vehicle and Motorist Age, Sex, and Seating Position
Characteristics
APPENDIX I Highways and Jurisdictions Surveyed
Belt Use %
(N) Jurisdictions
Vehicle Type Car Utility Pickup Passenger Van* Other Vans Unknown Estimated Age (years)
(Am J Public Health 1990; 80:740-742.)
Introduction Information on seat belt use is typically based on observations of motorists on city streets. For example, the National Highway Traffic Safety Administration (NHTSA) has surveyed belt use in 19 major cities annually since 1975.' However, belt use is known to vary according to where observations are made, and one location where belt use typically is higher than on city streets is interstate highways. In surveys in four states, belt use was 10-20 percentage points higher on interstate highways connecting the cities than in the cities.2 Systematic information on seat belt use in vehicles traveling outside cities is lacking. In the four-state study it was collected incidentally as observation teams traveled between cities.2 The present study provides information on belt use on interstate highways in the eastern United States and compares use rates in states and Canadian provinces with and without belt use laws. Methods Seat belt use observations were made by trained observers sitting behind the driver of a passenger van that traveled slower than the prevailing traffic in the far right lane. From that location, observers could clearly see shoulder belt use of front seat occupants of cars, light trucks, and vans passing in the adjacent lane. Lap belt use was not observed. Most cars on the road (all vehicles beginning with model year 1974) have integral lap/shoulder belts in the driver and right front seating positions. However, pre-1974 cars were not excluded so belt use is slightly underestimated. Belt use observations were made on 5,129 miles of interstate highways in 21 eastern states and on limited-access highways in two eastern Canadian provinces from 9 am to 4 pm weekdays in August 1988. Appendix I provides information on thejurisdictions and highways surveyed and belt use law status. It should be noted that the kinds of travel on these highways can vary tremendously from state to state. For example, in New York state, 1-95 is entirely urban with short distances between access points and large volumes of local traffic; in South Carolina the same interstate is entirely rural with relatively long distances between access points. From the Insurance Institute for Highway Safety. Address reprint requests to JoAnn K. Wells, Insurance Institute for Highway Safety, 1005 N. Glebe Road, Arlington, VA 22201. This paper, submitted to the Journal July 14, 1989, was revised and accepted for publication October 3, 1989. C 1990 American Journal of Public Health
AJPH June 1990, Vol. 80, No. 6
Observed differences in belt use for different populations were tested by x2 test of independence; only differences a = 0.05 are reported. Results Seat belt use by the 14,354 front seat occupants observed on the highways surveyed averaged 58 percent in the United States and 79 percent in Canada. Belt use ranged from 48 percent to 66 percent in the 21 states and was 76 percent in Ontario and 84 percent in Quebec (Table 1). In the United States use was higher in states with laws (60 percent) than states without laws (56 percent), but the range of use rates for states with and without laws overlapped considerably. There was no significant difference in belt use between states with laws permitting primary and secondary enforcement. The majority of occupants (57 percent) were in vehicles registered in the state or province in which they were observed. Of those traveling in out-of-state vehicles, motorists from jurisdictions with seat belt laws were more likely to use belts than motorists from non-law jurisdictions, whether observed in states with laws (66 vs 57 percent), provinces with laws (81 vs 74 percent), or non-law states (66 vs 56 percent). Belt use was higher among drivers; in cars, utility vehicles, and passenger vans; among those estimated to be age 25 or older; and among women (Table 2). Discussion Belt use on interstates is higher than belt use in cities in the same state. Even in states without laws, belt use on interstates was greater than 50 percent, about 20 percentage TABLE
1-Intwstaft Boft Use, by Jurisdiction Belt Use
Jurisdiction United States Law Connecficut Florida Illinois Indiana Maryland Michigan New Jersey New York North Carolina Ohio Pennsylvania Tennessee Virginia No Law Delaware
Georgia Kentucky Maine Massachusetts New Hampshire Rhode Island South Carolina Canada Ontario
Quebec
%
(N)
60 58 56 55 58 66 59 65 54 59 64 66 51 63 56 64 59 64 52 49 54 48 60
(7,943) (526) (2,149) (257) (311) (697) (581) (477) (98) (490) (453) (605) (476) (823) (3,311) (59)
76 84
(2,042) (1,058)
(1,265) (140) (711) (404) (63) (212)
(457)
Standard Error of Percent Belt Use 0.6 2.2 1.1 3.1 2.8 1.8 2.0 2.2 5.0 2.2 2.3 1.9 2.3 1.7 0.9 6.2 1.4 4.1 1.9 2.5 6.3 3.4 2.3 0.9 1.1
009040036/90$1.50 741
PUBLIC HEALTH BRIEFS TABLE 2-Interstate Seat Belt Use by Front Seat Occupants by Vehicle and Motorist Age, Sex, and Seating Position
Characteristics
APPENDIX I Highways and Jurisdictions Surveyed
Belt Use %
(N) Jurisdictions
Vehicle Type Car Utility Pickup Passenger Van* Other Vans Unknown Estimated Age (years)
