Transportation Expertise

Primary versus Secondary Enforcement of Safety Belt Use

Statewide mandatory safety belt use laws began to be enacted in the 1980s at the urging of the federal government. While these laws were initially unpopular in many states, every state except New Hampshire has now passed a safety belt use law. It is clear that implementation and enforcement of mandatory safety belt use laws increase safety belt use. An important component of legislation is the provision in the belt use law that indicates how the law is to be enforced. As states began to discuss adopting safety belt use laws, citizens voiced concerns that these laws were in violation of their individual rights or could be used by police as a way to harass citizens. To address these concerns, legislators in New Jersey included a “secondary” enforcement provision in their safety belt use law that stated that an officer could issue a safety belt citation only if the vehicle was stopped for a different violation. By including this provision in their law, New Jersey legislators created a distinction between secondary (an officer cannot stop a vehicle with an unbelted occupant unless some other violation is present) and primary enforcement (an officer can stop a vehicle and cite an occupant solely for failure to use a safety belt).

Direct observation studies conducted in each state show that states with standard enforcement have use rates that are higher than states with secondary enforcement. In recognition of the fact that belt use is higher in the presence of standard enforcement, many states that originally had secondary enforcement have begun to enact legislation to strengthen belt use laws to standard enforcement. UMTRI researchers have examined the differences in belt use between secondary and primary enforcement in Michigan, as well as studied many of the other effects of changing from secondary to primary enforcement.