Observations of seat belt use and interviews of drivers were made prior to the implementation of the seat belt law in Illinois and for 10 months thereafter in Urbana-Champaign.

Use of seat belts increased from about 12% prior to the law to about 40% in the first month (July 1985) and 48% in the next three months. By December, 1985 seat belt use had dropped to about 30% and remained there for the next 4 months. Similar trends were found in statewide surveys.

Drivers were not well informed about aspects of the law initially, over half supported it and most stated that increased enforcement and a greater fine would increase use.

By means of fatality data for nine months before and after the law and controling for exposure, it was estimated that the law reduced fatalities by 3 percent.