Speed and low-light conditions linked to drivers skipping seatbelts

Drivers who don’t wear their seatbelts were found to be doing it in situations when seatbelts would actually help the most, according to a new study by researchers from the Penn Medicine Nudge Unit. The analysis, published in Traffic Injury Prevention, highlighted that situations like driving after sundown or even at high speeds were more predictive of whether someone skipped a seatbelt than their demographics.

“Our study suggests that future seatbelt campaigns and other interventions may be more effective if they move beyond broad demographic targeting and, instead, focus on these moments when people are most likely to skip buckling,” said senior author M. Kit Delgado, MD, faculty director of the Nudge Unit and an associate professor of Emergency Medicine.

Seatbelts cut the risk of death and serious injury

Seatbelt usage has been found to cut people’s risk of death or serious injury in half, but one in 10 of those riding in the front seats of a vehicle don’t use them. As such, almost half of crash fatalities in the United States involve a person not wearing their seatbelt.

Delgado, lead author Jeffrey Ebert, PhD, director of Applied Behavioral Science at the Nudge Unit, and their colleagues decided to see if there were some commonalities in who didn’t use seatbelts and what situations non-usage of seatbelts occurred in.

Looking at data from 1,000 consenting participants over almost 130,000 trips­—gleaned from vehicle sensors, including ones in seatbelt latches—the researchers found that most people did use their seatbelts. Of all trips recorded, 84 percent included seatbelt use.

However, when a seatbelt was not used on a specific trip, the researchers determined that it was unrelated to the driver characteristics like sex, age, or where they lived. Instead, it was the details of the trip that mattered.

Drivers buckle up less at night and at higher speeds

The data showed that 30 percent of buckling behavior could be tied to “situational factors,” while not even 1 percent could be tied to demographics.

Drivers were 6 percent less likely to wear a seatbelt in the evening, and 13 percent less likely late at night.

For any given driver, a 10 mile-per-hour increase in speed was tied to a 2 percent drop in buckling.

Looking at when drivers did use their seatbelts, longer trips correlated with greater seatbelt use. The data showed that 74 percent of drivers taking a trip of five miles or less wore their seatbelts, but 95 percent buckled on longer trips.

Identifying a more targeted intervention

Currently, campaigns for seatbelt buckling are largely targeted widely, such as through electronic billboards and “Click-it or Ticket” advertisements.

But the Nudge Unit’s work points to an opportunity to more effectively reach people in situations where they might need the message.

At the same time, the team said that roughly 25 percent of individuals’ tendency to buckle up couldn’t be pinned down to a factor measured in the study. More research could potentially narrow down these unknown variables—which could include non-demographic considerations like personality traits—and lead to better interventions.

“The more we know about when people buckle up—and when they don’t—the more lives will be saved,” Ebert said.

The team has already had success in getting more drivers to buckle up. Offering cash incentives in a “game” challenging drivers to stack up seatbelt streaks resulted in more drivers using their seatbelts, even after the game ended.

“We have tested ways that seem effective in promoting this safer behavior,” Delgado said. “Combining all available information and our work in nudging appears especially promising.”

This work was supported by funding from the Abramson Faily Foundation and a grant from the Centers for Disease Control (R49CEE003083). It builds on previous findings in collaboration with General Motors.