I. INTRODUCTION

This report contains the 1998 results on seat belt use in Hawaii. Hawaii's mandatory seat belt law covers all front-seat passengers. It requires that all drivers and front-seat passengers use seat belts. Data were collected and analyzed by the University of Hawaii's Department of Urban and Regional Planning (UH). Field surveys were conducted at various sites on the four main Hawaiian islands during the months of January and February in 1998. The site selection and methodology employed was based on studies done in 1985 through 1997. During this year's study, 48,733 front seat occupants were observed.

II. SUMMARY

Since the last study in 1997, seat belt use has stabilized in Hawaii at 80.5%. While these numbers are above the national average, they are lower than the observed peak of 85.3% in 1991. The sharp increase in 1986 was the result of the implementation of the Hawaii seat belt use law. Prior to the that, seat belt use was only 33.0% in 1985. Figure 1 depicts these trends.

III. METHODOLOGY

For this study, seat belt use was recorded at 120 sites throughout Hawaii. Two trained observers were stationed at each site for approximately 40 minutes. One member was responsible for observing vehicles while the other recorded the data on a standardized survey form. The sampling and observation procedures were designed to be in compliance with federal guidelines developed by the US Department of Transportation, National Highway Safety Traffic Administration. Data were entered into personal computers at the UH. It was then uploaded to a UNIX workstation where statistical analysis was performed using SAS, a statistical software package.

IV. FINDINGS

This section discusses the study findings in detail. The results of the analysis are described according to four different aspects of seat belt use. It include details on:

(1) Differences by island

Figure 2 shows the 1998 seat belt use rate for the major Hawaiian islands. Kauai has the highest seat belt use rate at 85.3%, followed by Hawaii (81.5%), Oahu (79.8%), and Maui (77.9%).

Table 1 presents a more detailed breakdown of the seat belt use rate by island (complete table is found in the appendix section of this report). It also shows that drivers (82.3%) have a higher percentage of wearing seat belts than front seat passengers (75.9%). The difference between drivers' and passengers' seat belt use is the greatest on Oahu where 82.5% of drivers and 72.7% of passengers used seat belts. Kauai has 86.3% of drivers and 82.9% of passengers wearing seat belts. Hawaii has 82.6% of drivers and 78.8% of passengers wearing seat belts. Maui, which had the smallest difference among the four islands, has 78.6% use rate for drivers and 76.4% for passengers. Site specific seat belt use rates for all islands are found on maps located in the appendix of the report.

Figures 3 to 6 shows the overall seat belt use by year on the four major Hawaiian islands. Oahu has seen a decline in its seat belt use in recent years. Peak rate was observed in 1991 where 87.7% of vehicle occupants were observed using belts (Figure 3). This was the highest seat belt use rate ever recorded in Hawaii. In 1998, Oahu's seat belt use rate is 79.8%.

Maui, however, has seen an increase in seat belt use. Its peak year was 1993 where 81.7% of vehicle occupants were observed using seat belts (Figure 4). In 1998, Maui's seat belt use is 77.9%. Since the survey began, Maui has consistently ranked low on seat belt use rate of the major Hawaiian islands.

The island of Hawaii, like Maui, has seen an increase in seat belt use recently. Its peak use rate was 83.2% recorded in 1993 (Figure 5). In 1998, its seat belt use is 81.5%.

Remarkably, Kauai has shown consistent gains in seat belt use throughout the survey period. In 1998, 85.3% of vehicle occupants were observed using seat belts which is also its peak (Figure 6).

(2) Differences by factors

When examining the seat belt use rate, it is important to consider the different factors that influence drivers' and passengers' decision to wear their seat belts. Figure 7 shows the seat belt use rate of drivers and front seat passengers by vehicle type. Drivers and passengers in cars are more likely to be belted (83.2%) then any other vehicle type. While seat belt use rate in vans (80.2%) are the closest to that of cars. Finally, trucks had the lowest use rate at 70.5%. These results are consistent with previous surveys.

Figure 8 shows the seat belt use rate of drivers and passengers under different weather conditions. In 1998, seat belt use under sunny conditions is 81.0%. The rate increased under partly cloudy conditions to 84.3%. However, it decreased under cloudy conditions (72.1%). The low numbers recorded at outlying areas may provide a partial explanation for this.

Vehicle occupants are more likely to wear seat belts as the speed limit increases. Figure 9 shows these trends.

Figure 10 shows that as the number of lanes increases, vehicle occupants are more likely to wear their seat belts (although a slight decrease in belt use was recorded in the fourth lane).

Figure 11 shows seat belt use characteristics between weekday and weekend. It shows that weekday occupants are more likely to use seat belts than weekend travelers.

Table 2 gives a detailed breakdown of the seat belt use rate (the complete table is found in the appendix section of this report).

(3) DIFFERENCES BY GENDER

The methodology employed for this section is similar to that which is found in Section III of this report. The major difference is that 10 sites were selected throughout Oahu. Two trained observers were stationed at each site for approximately 40 minutes. The first 20 minutes was spent observing one gender while the rest of the time was spent recording the other. One member was responsible for observing vehicles while the other recorded the data on a standardized survey form. Then the data was processed and analyzed as per methodology section in this report.

Figure 12 shows that females (82.1%) are more likely to use seat belts than males (79.6%).

Table 3 shows the breakdown of the factors that affect the seat belt use rate by gender.

(4) DIFFERENCES BETWEEN DAY AND NIGHT TIME PERIODS

The methodology employed for this section is similar to that which is found in Section III of this report. The major difference is that 10 well-lighted sites were selected throughout Oahu. These sites are then compared to observations taken during day time hours. Two trained observers were stationed at each site for approximately 40 minutes. One member was responsible for observing vehicles while the other recorded the data on a standardized survey form. Then the data was processed and analyzed as per methodology section in this report.

Figure 13 shows that occupants are more likely to wear their seat belts during the day (82.6%) than at night (82.0%). These results are consistent with previous surveys.

Table 4 shows the breakdown of the seat belt use rate between day and night time periods.

V. CONCLUSION AND RECOMMENDATIONS

Since the last report, seat belt use has stabilized at 80.5% statewide. While these numbers are above the national average, they are lower than the observed peak of 85.3% in 1991. Because the overall frequency for statewide observations is very large, the statistical margin of error is small. In the 1998 study, with 95% confidence, the margin of error is +0.35% for the statewide totals. Because of the smaller number of observations on the neighbor islands, the margin of error increases to +0.83% to +0.91%, depending on the county.

These findings suggest several recommendations:

APPENDICES

Hawaii Survey

Maui Survey

Oahu Island Survey

Oahu Urban Survey

Kauai Survey