The explanation appears to be related to the fact that drivers are not a homogeneous population. Drivers who generally exhibit more risk-taking behaviour and who have the most automobile accidents, are the least likely to comply voluntarily with the seat belt law, and are the last drivers to be affected by enforcement programs.
In: Advances in belt restraint systems, design, performance and usage : proceedings of the international congress and exposition, Detroit, Michigan, February 27 - March 2, 1984, p. 161-171, graph., tab., ref.; SAE Paper No. 840329.
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