III. Results
Observations were done between September and November 2004 except for one tribal reservation, where observations were done in February 2005. Overall sample characteristics are shown in Table 3. A total of 10,095 vehicles were observed, with 3,495 additional passengers.
Approximately 44 percent of the vehicles were cars, 31 percent were pickups, 14 percent were SUVs, and 10 percent were vans. Fifty-eight percent of drivers were male, and 38 percent were female; gender could not be coded for 3 percent of drivers. Fifty-three percent of passengers were female, just 37 percent were male, and gender could not be coded for 10 percent.
Belt use could be coded for 90 percent of drivers and 83 percent of passengers. Somewhat higher percentages of unknown belt use were associated with trucks (14 percent, drivers; 24 percent, passengers), SUVs (13 percent, drivers; 19 percent, passengers), vans (19 percent, passengers), foggy conditions (17 percent, drivers; 37 percent, passengers), and rural roads (12 percent, drivers; 22 percent, passengers). Belt use could not be coded for about 88 percent of drivers and passengers whose sex could not be coded.
Table 3. Observation Sample Overview.
4,455 |
3,152 |
1,438 |
1,049 |
1 |
10,095 |
44.1% |
31.2% |
14.2% |
10.4% |
0.0% |
|
| |
|
5,876 |
3,873 |
346 |
|
|
10,095 |
58.2% |
38.4% |
3.4% |
|
|
|
| |
|
1,292 |
1,857 |
346 |
|
|
3,495 |
37.0% |
53.1% |
9.9% |
|
|
|
Because we were unable to make safety belt use observations on the Navajo reservation, the scope of these observations could perhaps be better described as “Indian Country Excluding Navajo.”
For Indian Country Excluding Navajo, the overall safety belt use rate was 55.4 percent.
There was very large variation in belt use across tribal reservations, ranging from a low of 8.8 percent to a high of 84.8 percent. Reflecting this variability, the standard error of measurement was 2.5 percent, and the relative standard error (standard error divided by average belt use) was 4.6 percent. The 95 percent confidence interval for overall belt use was 50.5 percent to 60.4 percent.
As shown in Table 4, there were significant differences in belt use by vehicle type and occupant gender for drivers and passengers. Rates were higher for cars (58.8 percent), SUVs (62.1 percent), and vans (57.5 percent) and much lower for pickup trucks (48.1 percent).
Males were less likely to use safety belts than females, 52.3 percent vs. 60.3 percent. Drivers were somewhat more likely to be belted, at 56.6 percent, than passengers, at 51.3 percent. The lowest overall belt use rate was for male passengers in pickups, at just 39.1 percent. The highest rate was for female drivers of SUVs, 67.7 percent belted.
Belt use also varied consistently by road type. Within towns on collector roads, overall belt use was 59.0 percent, while the rate on the more rural between-town arterials was 51.0 percent.
Table 4. Safety Belt Use, by Vehicle, Occupant, Area, and Road Type.
56.6% |
9,064 |
51.3% |
2,883 |
55.4% |
11,947 |
60.3% |
4,122 |
53.7% |
1,431 |
58.8% |
5,553 |
49.2% |
2,723 |
43.9% |
736 |
48.1% |
3,459 |
63.5% |
1,265 |
56.1% |
392 |
62.1% |
1,657 |
58.5% |
954 |
54.7% |
324 |
57.5% |
1,278 |
54.0% |
5,377 |
44.4% |
1,154 |
52.3% |
6,531 |
61.3% |
3,646 |
56.7% |
1,684 |
60.3% |
5,330 |
59.5% |
5,182 |
57.2% |
1,662 |
59.0% |
6,844 |
52.2% |
3,882 |
47.9% |
1,221 |
51.0% |
5,103 |
Areas
Three of the had multiple tribal reservations. The Northern Plains area had the five lowest belt use rates and averaged just 27.6 percent belt use across all five. Great Lakes and Northwest had the highest belt use; three of the four reservations in those two areas had the highest individual belt use rates observed. Of the five reservations in the Southwest, three had moderate belt use figures, while the other two had rates above 75 percent, among the highest for Indian Country.
Belt Use Laws
Another indication of belt use is the kind of safety belt law. There are two kinds of belt use laws that may affect use rates: the safety belt law of the tribal reservation itself and the safety belt law of the State in which the tribal reservation is located. Data were examined both ways.
Nine tribal reservations had primary safety belt laws; in them, 68.6 percent of vehicle occupants were belted. By comparison, three tribal reservations had secondary belt laws; they averaged
53.2 percent belt use. For the four tribal reservations with no belt use law of any kind, only 26.4 percent of the vehicle occupants were belted.
Also, nine tribal reservations were located in States with primary belt use laws. Those nine tribal reservations were the nine with best use rates; they averaged 72.8 percent belted occupants. The remaining seven tribal reservations, in States with secondary belt use laws, were the lowest-usage tribal reservations; they averaged just 33.3 percent buckled occupants.