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TRAFFIC SAFETY FACTS Research Note

DOT HS 812 465 December 2017

Seat Belt Use in 2017—Overall Results Seat belt use in 2017 was 89.7 percent, not statistically differ- ent at the 0.05 level from 90.1 percent in 2016. This result is from the National Occupant Protection Use Survey (NOPUS), the only survey that provides nationwide probability-based observed data on seat belt use in the United States. The NOPUS is conducted annually by the National Center for Statistics and Analysis of the National Highway Traffic Safety Administration.

Seat belt use has shown an increasing trend since 2000, accom- panied by a steady decline in the percentage of unrestrained passenger vehicle (PV) occupant fatalities during the daytime (Figure 1). The 2017 survey also found the following:

■■ Seat belt use for occupants in the West is higher than in the other regions, Northeast, Midwest, and South, in 2017 (Figure 2).

■■ Seat belt use continued to be higher in the States in which vehicle occupants can be pulled over solely for not using seat belts (“primary law States”) as compared with the States with weaker enforcement laws (“secondary law States”) or without seat belt laws (Figure 3).

■■ Seat belt use for occupants in Midwest increased signifi- cantly from 85.5 percent in 2016 to 88.6 percent in 2017 (Table 1).

Figure 1 National Seat Belt Use Rate and Daytime Percentage of Unrestrained Passenger Vehicle Occupant Fatalities

30%

45%

60%

75%

90%

=1=1=1=1=1=1=1=1=1=1=1=1=1=1=1=1=1=1 30%

45%

60%

75%

90%

=1=1=1=1=1=1=1=1=1=1=1=1=1=1=1=1=1=1

51.6%

70.7%

50.3% 49.9%

75.2%73.1%

47.4% 46.9%

79.2%

2000

79.5%

2001

47.2%

81.7%

2002

46.1%

81.2%

2003

44.5%

82.5%

2004

83.1%

2005

45.0%

2006

44.3%

84.1%

2007

42.4%

85.1%

2008 2009

43.1%

83.8%

2010

43.2% 39.9% 40.4% 40.2% 40.7%

86.1%

2011 2012 2013 2014 2015 2016 2017

87.2% 86.7% 88.5% 90.1% 89.7%

Pe rc

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Pe rc

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nr es

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ne d

Belt Use Rate Daytime Percent Unrestrained PV Occupant Fatalities

Source: NOPUS and FARS

Figure 2 Seat Belt Use by Region

50%

60%

70%

80%

90%

100%

MidwestNortheast

2016 2017

South West

86.5% 90.9% 88.6%85.5%

88.9% 94.5%93.4%90.9%

Se at

B el

t U se

, in

P er

ce nt

Source: NOPUS

Figure 3 Seat Belt Use by Law Type

50%

60%

70%

80%

90%

100%

Primary Law States

2016 2017

Other Law States

90.9%92.1%

83.0% 85.7%

Se at

B el

t U se

, in

P er

ce nt

Source: NOPUS

1The FARS 2017 data on the percentage of unrestrained passenger vehicle occupant fatalities during daytime will be available later in 2018.

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NHTSA’s National Center for Statistics and Analysis 1200 New Jersey Avenue SE., Washington, DC 20590

Table 1 Seat Belt Use by Major Characteristics

Occupant Group1

2016 2017 2016–2017 Change

Belt Use2 95% Confidence

Interval3 Belt Use2 95% Confidence

Interval3 Change in

Percentage Points 95% Confidence

Interval4 P-value5

All Occupants 90.1% (88.5, 91.5) 89.7% (88.2, 91.0) -0.5 (-2.2, 1.3) 0.59 Drivers 90.5% (88.9, 92.0) 90.2% (88.7, 91.5) -0.4 (-2.2, 1.4) 0.65 Right-Front Passengers 88.6% (86.8, 90.2) 87.9% (86.1, 89.4) -0.7 (-2.8, 1.3) 0.48

Occupants in States With6

Primary Enforcement Laws 92.1% (90.8, 93.2) 90.9% (89.2, 92.3) -1.2 (-3.1, 0.7) 0.21 Secondary/No Enforcement Laws 83.0% (77.6, 87.3) 85.7% (82.4, 88.5) 2.7 (-0.9, 6.3) 0.13

Occupants Traveling on Expressways 92.7% (90.5, 94.3) 92.5% (90.9, 93.9) -0.1 (-1.9, 1.6) 0.90 Surface Streets 88.3% (86.5, 90.0) 87.8% (85.8, 89.5) -0.6 (-2.6, 1.5) 0.57

Occupants Traveling in Fast Traffic 92.0% (90.0, 93.7) 91.5% (89.9, 92.9) -0.5 (-2.6, 1.6) 0.61 Medium-Speed Traffic 88.6% (86.2, 90.7) 89.1% (86.6, 91.2) 0.5 (-1.6, 2.5) 0.65 Slow Traffic 87.5% (84.6, 90.0) 86.0% (83.8, 87.9) -1.6 (-4.2, 1.1) 0.23

Occupants Traveling in Heavy Traffic 92.3% (90.9, 93.5) 91.6% (90.1, 92.8) -0.7 (-2.3, 0.8) 0.33 Moderately Dense Traffic 88.3% (85.7, 90.5) 88.1% (86.1, 89.8) -0.2 (-2.7, 2.2) 0.85 Light Traffic 81.5% (79.1, 83.8) 82.0% (78.3, 85.2) 0.5 (-2.9, 3.8) 0.79

Occupants Traveling Through Light Precipitation 89.3% (83.2, 93.4) 89.8% (86.5, 92.4) 0.5 (-5.1, 6.1) 0.86 Light Fog 91.0% (85.5, 94.6) 90.8% (81.7, 95.6) -0.2 (-8.0, 7.5) 0.95 Clear Weather Conditions 90.2% (88.5, 91.6) 89.6% (88.1, 91.0) -0.5 (-2.2, 1.1) 0.52

Occupants in Passenger Cars 91.1% (89.6, 92.4) 90.6% (89.2, 91.8) -0.5 (-1.9, 0.9) 0.46 Vans and SUVs 92.3% (91.0, 93.5) 91.7% (90.1, 93.0) -0.6 (-2.6, 1.3) 0.50 Pickup Trucks 83.2% (79.7, 86.1) 83.2% (80.6, 85.6) 0.1 (-3.3, 3.5) 0.97

Occupants in the Northeast 90.9% (87.5, 93.4) 86.5% (82.8, 89.5) -4.4 (-9.1, 0.4) 0.07 Midwest 85.5% (79.7, 89.9) 88.6% (85.0, 91.4) 3.1 (0.1, 6.0) 0.04 South 90.9% (89.0, 92.5) 88.9% (86.1, 91.2) -2.0 (-5.4, 1.4) 0.24 West 93.4% (89.6, 95.9) 94.5% (92.2, 96.1) 1.0 (-0.5, 2.6) 0.18

Occupants in Urban Areas 90.5% (88.9, 91.9) 90.2% (88.7, 91.5) -0.3 (-2.0, 1.3) 0.69 Rural Areas 89.5% (86.9, 91.6) 88.7% (86.1, 90.9) -0.7 (-3.5, 2.1) 0.59

Occupants Traveling During Weekdays 90.0% (88.3, 91.5) 89.5% (87.9, 91.0) -0.5 (-2.4, 1.4) 0.61

Weekday Rush Hours 89.9% (88.3, 91.4) 89.7% (88.0, 91.2) -0.3 (-2.3, 1.8) 0.80 Weekday Non-Rush Hours 90.1% (87.9, 91.9) 89.4% (87.2, 91.2) -0.7 (-2.7, 1.3) 0.48

Weekends 90.4% (88.4, 92.1) 90.0% (88.5, 91.4) -0.4 (-2.0, 1.2) 0.62 1 Drivers and right-front passengers of all observed passenger vehicles 2 Shoulder belt use observed from 7 a.m. to 6 p.m. 3 The Wilson Confidence Interval has the form: {(2nEFFp + t2) ± t√(t2 + 4nEFFpq)}/2(nEFF + t2), where p is the estimated percentage of Belt Use, nEFF = n/DEFF is the effective

sample size (where n is the sample size and DEFF is the design effect), t ≡ t1–α/2(df ), is a multiplier from the t-distribution with df degrees of freedom, and q = 1 – p. For percentages these endpoints are multiplied by 100.

4 The regular symmetric interval was used for the estimated change in percentage point, which is in the form: p ± t1–α/2(df )√v(p), where p is the estimated change in percentage point, v(p) is its estimated variance, and t1–α/2(df ) is a multiplier from the t-distribution with df degrees of freedom.

5 A p-value of 0.05 or less indicates that there is a statistically significant difference (at the alpha=0.05 level) between the 2015 and 2016 estimates for the group in question, indicated with bold type.

6 Use rates reflect the laws in effect at the time data were collected. Data Source: National Occupant Protection Use Survey, National Highway Traffic Safety Administration, National Center Statistics and Analysis.

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Survey Methodology The National Occupant Protection Use Survey is the only nationwide probability-based observational survey of seat belt use in the United States. The survey observes seat belt use as it actually occurs at randomly selected roadway sites, and thus provides the best tracking of the extent to which passenger vehicle occupants in this country are buckling up.

The survey data is collected by sending trained observ- ers to probabilistically sampled roadways, who observe passenger vehicles between the hours of 7 a.m. and 6 p.m. Observations are made either while standing at the road- side or, in the case of expressways, while riding in a vehicle in the traffic. In order to capture the true behavior of pas- senger vehicle occupants, the NOPUS observers do not stop vehicles or interview occupants. The 2017 NOPUS data was collected from June 5 to July 1, 2017, while the 2016 data was collected from June 6 to June 25, 2016.

The NOPUS uses a complex, multistage probability sample, statistical data editing, imputation of unknown values, and complex estimation procedures. The sample sites for the 2017 NOPUS were the same as that from the 2016 NOPUS sample sites. Table 2 shows the observed sample sizes of the 2017 NOPUS Moving Traffic Survey. A total of 125,712 occu- pants were observed in the 101,503 vehicles at the 1,966 data collection sites.

Table 2 Sites, Vehicles, and Occupants* Observed

Numbers of 2016 2017 Percentage Change

Sites Observed 1,966 1,966 0.00%

Vehicles Observed 100,776 101,503 0.72%

Occupants Observed* 124,746 125,712 0.77%

* Drivers and right-front passengers only.

Because the NOPUS sites were selected probabilistically, we can analyze the statistical significance of the results. Statistically significant increases in seat belt use from 2016 to 2017 are identified in Table 1 by a p-value that is 0.05 or less in the table’s far-right column.

Data collection, estimation, and variance estimation for the NOPUS are conducted by Westat, Inc., under the direction of NHTSA’s National Center for Statistics and Analysis under Federal contract number DTNH22-13-D-00284.

Definitions Under NOPUS observation protocols, a driver or right-front passenger is considered “belted” if a shoulder belt appears to be across the front of the body.

A jurisdiction that can enforce traffic laws, such as a State or the District of Columbia, has a “primary enforcement law” if occupants can be ticketed simply for not using their seat belts. Under “secondary enforcement laws” an occupants must be stopped for another violation, such as an expired license tag, before being cited for seat belt nonuse. As of May 31, 2017, primary laws were in effect in 34 States and the District of Columbia, 15 States had secondary laws, and 1 State (New Hampshire) effectively has no adult seat belt laws. (In New Hampshire, it is legal for occupants over age 18 to ride unbelted.). Table 3 provides a list of the States with “primary enforcement laws.”

Table 3 States With Primary Enforcement Seat Belt Laws*

Alabama Hawaii Michigan Rhode Island

Alaska Illinois Minnesota South Carolina

Arkansas Indiana Mississippi Tennessee

California Iowa New Jersey Texas

Connecticut Kansas New Mexico Utah

Delaware Kentucky New York Washington

District of Columbia Louisiana North Carolina West Virginia

Florida Maine Oklahoma Wisconsin

Georgia Maryland Oregon

* States with laws in effect as of May 31, 2017.

“Expressways” are defined to be roadways with limited access, while “surface streets” comprise all other roadways. “Rush hours” are defined as the time periods 7 to 9:30 a.m. and 3:30 to 6 p.m.

A roadway is defined to have “fast traffic” if during the observation period the average speed of passenger vehicles that pass the observer exceeds 50 mph, with “medium-speed traffic” defined as 31 to 50 mph and “slow traffic” defined as 30 mph or slower.

A roadway is defined to have “heavy traffic” if the average number of vehicles on the roadway during the observation period is greater than 5 per lane per mile, with “moderately dense traffic” defined as greater than 1 but less than or equal to 5 vehicles per lane per mile, and “light traffic” as less than or equal to 1 vehicle per lane per mile.

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The survey uses the following definitions of geographic regions, which are defined in terms of the States contained in the region below:

Northeast: CT, MA, ME, NH, NJ, NY, PA, RI, VT

Midwest: IA, KS, IL, IN, MI, MN, MO, ND, NE, OH, SD, WI

South: AL, AR, DC, DE, FL, GA, KY, LA, MD, MS, NC, OK, SC, TN, TX, VA, WV

West: AK, AZ, CA, CO, HI, ID, MT, NM, NV, OR, UT, WA, WY

Seat belt use rates reflect the State laws in effect at the time of data collection.

For More Information This Research Note was written by Hongying (Ruby) Li and Timothy M. Pickrell, mathematical statisticians in the Mathematical Analysis Division, National Center for Statistics and Analysis, NHTSA. For questions regarding the information presented in this document, please contact [email protected].

Additional data and information on the survey design and analysis procedures will be available in upcoming publica- tions to be posted at the website https://crashstats.nhtsa.dot. gov/#/.

Research has found that lap/shoulder seat belts, when used, reduce the risk of fatal injury to front-seat passenger car occupants by 45 percent and the risk of moderate-to-critical injury by 50 percent. In 2016 alone, seat belts saved an esti- mated 14,668 lives (Traffic Safety Facts: Lives Saved in 2016 by Restraint Use and Minimum-Drinking-Age Laws, NHTSA, Report No. DOT HS 812 454). For more information on the campaign by NHTSA and the States to increase seat belt use, see www.nhtsa.gov/CIOT.

The NOPUS also observes other types of restraints, such as child restraints and motorcycle helmets, and observes driver electronic device use. This publication is part of a series that presents overall results from the survey on these top- ics. Please refer to the upcoming research notes and techni- cal reports in the series, such as “Motorcycle Helmet Use in 2017—Overall Results,” for the latest data on these topics.

Suggested APA format citation for this report:

Li, R., & Pickrell, T. M. (2017, December). Seat belt use in 2017— Overall results. (Traffic Safety Facts Research Note. Report No. DOT HS 812 465). Washington, DC: National Highway Traffic Safety Administration.

This research note and other general information on highway traffic safety may be accessed by Internet users at: https://crashstats.nhtsa.dot.gov/#/.

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