Persistent audible belt reminders are no less effective at promoting belt use than interlocks, according to research by the Insurance Institute for Highway Safety (IIHS).

And researchers found that persistent reminders could save nearly 1,500 lives a year if all vehicles were equipped with them.

IIHS researchers conducted two studies that build off earlier research about the best ways to close the remaining belt use gaps. Seat belts reduce the risk of death among front-row occupants in crashes by 45 percent. About 90 percent of drivers and front passengers use seat belts, but nearly half of front-seat occupants killed in crashes aren’t belted.

In the first of the new studies, 49 part-time belt users who had recently received a seat belt citation drove two vehicles with different seat-belt reminders or a speed-limiting interlock for one week each. The data was combined with data from an earlier study, also involving part-time belt users with recent citations, that compared a gear-shift interlock with an audible belt reminder consisting of three seven-second periods of chiming, a minute or more apart (see “Gearshift interlocks could get more people to buckle up”, Nov. 21, 2017).

For the latest research, some participants first drove a car with the same fairly minimal belt reminder as used in the first study. They then drove either a car with a 100-second audible reminder or a car with an audible reminder that lasted indefinitely, until the person buckled. A third group drove cars with the 100-second reminder first and then a car equipped with a prototype speed-limiting interlock. The interlock restricted vehicle speed to 15 mph if either the driver or front passenger was unbelted.

The researchers concluded that the speed-limiting interlock, the indefinite reminder and the 100-second constant reminder all increased belt use by 30-34 percent compared with the intermittent reminder. The gear-shift interlock increased belt use 16 percent relative to the intermittent reminder.

The researchers calculated that increasing belt use by 34 percent in all vehicles on U.S. roads would save 1,489 lives each year.

“We expected the interlocks to be more effective than any type of belt reminder, but that didn’t turn out to be the case,” said HLDI Senior Research Scientist David Kidd, the study’s lead author. “Many people simply forget to buckle up, so a persistent reminder works well for them. For those who are really averse to using the seat belt, an interlock doesn’t always help because they can find a way to get around it, for example by buckling the belt behind their back or sitting on top of it.”