Modeling the impact of rescinding Michigan's primary and secondary seat belt laws on death and injury from passenger vehicle crashes.

Background: Seat belts are the most effective method of decreasing fatal and nonfatal motor vehicle crash injury. Advocacy groups have recently been successful in enacting repeals of mandatory motorcycle helmet laws in several states. In some states, this has prompted renewed efforts aimed at repealing mandatory seat belt laws.

Purpose: To evaluate and quantify the potential impact of rescinding seat belt laws on annual crash-related fatalities, nonfatal injuries, and associated economic costs, using Michigan as a model, to inform the national debate.

Methods: Proportional injury rates were calculated utilizing police-reported statewide passenger vehicle crash data from 1999 and 2002, where belt use rates approximate estimates associated with repeal of primary and secondary seat belt laws. Proportional rates were applied to the most recent year of crash data (2011) to estimate changes in statewide fatalities and nonfatal injuries. National cost estimates were applied to injury data to calculate associated economic costs.

Results: Full repeal of the seat belt law is estimated to result in an additional 163 fatalities, 13,722 nonfatal injuries, and an associated societal cost of $1.6 billion annually. Repeal of the primary seat belt law only is estimated to result in an additional 95 fatalities, 9156 nonfatal injuries, and an associated societal cost of $1.0 billion annually.

Conclusions: This analysis suggests that repealing the either the primary or full seat belt law would have a substantial and negative impact on public health, increasing motor vehicle crash related fatality, nonfatal injury, and associated economic costs.