Revival of Seatbelt Interlock Could Save Lives, Researchers Say

Ignition interlocks that restrict a vehicle from being started until occupants fasten their seatbelts could reduce traffic fatalities 16% by 2050, Australian road safety researchers say.

Center for Automotive Safety Research experts used three datasets to examine the vehicle age profiles of drivers who were not wearing seatbelts. These included an observational study from 2009, hospital admission data from 2008-2010 and coroner’s report data from 2008.

In each dataset, those not wearing a seatbelt were driving older vehicles than those who were belted. Overall seatbelt usage was 98% in the observational data, 89% in the hospital admissions data and 66% in the coroner’s data.

Researchers Daniel Searson and Robert Anderson, based at the University of Adelaide, used a hypothetical scenario in which seatbelt interlocks were made mandatory in all new vehicle models between 2015 and 2050.

It was assumed that without the presence of ignition interlocks, the vehicle age profiles for the unrestrained drivers would stay the same, as would the proportions of unrestrained drivers.

Under these assumptions, by 2030 ignition interlocks would be present for about 60% of all otherwise unrestrained drivers (based on the observational data), about 45% of otherwise unrestrained fatally injured drivers (based on coroner’s data) and around 40% of otherwise unrestrained drivers that would require hospital admission.

Ignition interlocks would approach 100% saturation in these three groups by around 2050.

The vehicle-age profiles from each dataset were then used to examine the time it would take for interlocks to be found in vehicles driven by those who would otherwise not be wearing a seatbelt.

These results were then used to calculate a “strongest case” estimate of the potential effectiveness of seatbelt interlocks.

The researchers found that by 2030 there would be a potential 2% reduction in injuries requiring hospital admission and a 7% reduction in fatalities. By 2050 these values would approach 5% and 16%, respectively.

“These reductions would apply on top of any casualty savings already made through enhanced vehicle technologies, infrastructure and regulations,” the researchers say.

“Despite the relatively long time required for interlocks to reach maximum effectiveness, the low cost and complexity of introducing seatbelt interlocks merits some encouragement, with some consideration given to aftermarket installation targeting users who are at high risk.”

Seatbelt reminders are required to obtain a 5-star rating under the Australasian New Car Assessment Program. The center report says that in vehicles with seatbelt reminders, the additional cost of installing an interlock system is low, as all that is needed is additional circuitry or onboard logic that links the seatbelt reminder sensors to the ignition system.

Forty years ago, NHTSA made ignition interlocks mandatory on all ’74 model vehicles sold in the U.S. Despite some early research indicating public acceptance of interlocks, there was widespread backlash about the regulation and a year later the law was repealed.

“In hindsight, the backlash over the law might have been predictable, given that only one in four people wore a seatbelt at the time,” the Australian report says.

Since then, there has been little research on interlock effectiveness, with most research being focused on reminder systems, which give an audio and visual warning when an occupant has not fastened his seatbelt.