A special belt use law enforcement and publicity campaign in Modesto, California has shown that techniques that increased belt use in jurisdictions with primary enforcement laws can be extended to states with secondary enforcement, although the effects may be smaller. Belt use among front-seat occupants covered by the law just before the campaign was thirty-two percent in Modesto compared to twenty-eight percent in Visalia, a comparison community about 125 miles away. Belt use reached a high of fifty-six percent during the campaign and was still forty-seven percent six months later; meanwhile, in Visalia, belt use declined slightly, to twenty-seven percent. Belt use increased among all subgroups but was lower in pickups and vans than in cars and station wagons, on Friday nights than on weekdays, among men than among women, among passengers than among drivers, and among younger than among older occupants. The campaign may also have caused some Modesto residents to believe their law could be enforced on a primary basis.