Enhanced seat belt reminder systems could save more than 1,000 lives every year, according to a recent report by a Transportation Research Board committee that includes psychologists, automotive safety engineers and other experts.

At Congress's request, the committee, chaired by psychologist William C. Howell, PhD, of Arizona State and Rice universities, reviewed both published and proprietary research to explore ways to increase seat belt use. The committee--which also included psychologist Patricia DeLucia, PhD, of Texas Tech University, and Allan Williams, PhD, a psychologist with the Insurance Institute for Highway Safety--determined that a reminder system that is more persistent than the currently mandated 4- to 8-second warning light and buzzer could increase seat belt use by as much as 5 percentage points if all vehicles had enhanced systems. "Even an increase of 1 percentage point would save hundreds of lives every year," says Howell.

Regulations without scientific basis

In fact, Congress's 1974 decision to prohibit the National Highway Traffic Safety Administration (NHTSA) from requiring any seat belt reminder system more insistent than an 8-second warning light and buzzer wasn't based on empirical data. At the time, NHTSA required 60-second flashing light and buzzer warnings, and either airbags or an unpopular interlock device that prevented vehicles from starting when seat belts were not buckled. Most model year 1974 automobiles were outfitted with the interlock system, and the devices were so unpopular that Congress passed the legislation to limit NHTSA's regulatory authority.

While today's shorter reminder chimes are acceptable to the driving public, they may not be any more effective than having no reminder at all, shows research conducted by the NHTSA in 1976. In a study of 5,429 drivers of rental cars, researchers found that drivers in cars equipped with 8-second seat belt reminder systems did not buckle up any more than drivers without the buzzer and light warning.

"People have become so habituated to the seat belt warning, they just sort of tune it out," explains Howell. "A lot of people report that they don't even notice it anymore."

In the last few years, some automotive manufactures have voluntarily developed enhanced means of reminding drivers to use seat belts, and the committee examined a few of them. For example, Ford, the only company to deploy such a system in the United States, has developed the "BeltMinder." The system chimes intermittently for up to five minutes, sounding for 6 seconds then pausing for 30, if a driver fails to buckle up. It increased seat belt use by 5 percent in preliminary research conducted by the Insurance Institute for Highway Safety.

"On first blush, the Ford technology is more effective than the 4- to 8-second reminder," says study director Nancy Humphrey of the committee report.

Results from NHTSA's interviews and focus groups dovetail with the Insurance Institute research. Of 141 drivers questioned, 78 percent predicted the Ford system would effectively remind them to use a seat belt, but more importantly 71 percent reported that the Ford system was "acceptable"--that they wouldn't mind buying a car with such a system in place. According to the report, some part-time seat belt users even said they would welcome the reminder to buckle up.

And part-time seat belt users, who represent the one-fifth of drivers who will buckle up depending on the situation, may benefit the most from enhanced seat belt reminder systems, notes the committee.

"They might buckle up on the beltway, but not on a five-minute trip to the store," Howell explains, noting that the NHTSA research found that nearly three-quarters of these drivers predict the in-car reminder systems to be at least somewhat effective.

However, the small percentage of drivers who are hard-core non-users would need more intrusive measures to persuade them to use seat belts, the report says. These drivers, notes Howell, object to seat belts on philosophical grounds or may erroneously believe that seat belts are likely to trap them in their car in a crash. Further research is needed to find ways to reach committed non-users, the committee reports.

Empirical data is also needed to serve as the foundation of future seat belt reminder standards. For example, researchers could study the optimal volume of a reminder chime or the seat belt reminder system's interaction with other new safety features, such as early collision warnings, says the study committee.

"If Congress lifts the limiting statute and the [NHTSA] decides to regulate," says Howell, "they need the good science, including the human factors results, in order to require the best-designed system."

Further Reading

  • Bentley, J.J., Kurrus, R., & Beuse, N. (2003). Qualitative research regarding attitudes towards four technologies aimed at increasing safety belt use (Report 2003-01). Bethesda, MD: Equals Three Communications.

  • Bradbard, S.L., Panlener, J.C., & Lisboa-Farrow, E. (1998). Increasing seat belt use among part-time users: Messages and strategies (DOT-HS-808-708). Washington, DC: U.S. Department of Transportation. 

  • Calisir, F., & Leto, M.R. (2002). Young drivers: Decision making and safety belt use. Accident Analysis and Prevention, 34(6), 793-805.

  • Harrison, W.A., Senserrickm T.M., & Tingvall, C. (2000). Development and trial of a method to investigate the acceptability of seat belt reminder systems (Report 170). Victoria, Australia: Monash University Accident Research Centre.

  • Howell, W.C., Champion, D.A., DeLucia, P.R., Dinh-Zarr, T.B., Finkelstein, M.M., Haseltine, P.W., et al. (2003). Buckling up: Technologies to increase seat belt use (Report 278). Washington, DC: Transportation Research Board.

  • Westefeld, A., & Phillips, B.M. (1976). Effectiveness of various safety belt warning systems (DOT-HS-801-953). Washington, DC: U.S. Department of Transportation.