Other studies, however, have suggested the helmet laws may influence helmet use among children and young adolescents. In one such study (Ni, Sacks, Curtis, Cieslak, & Hedberg, 1997), researchers observed helmet use among bicyclists before and after the implementation of an Oregon law that required children younger than 16 years to use a helmet when bicycling on public property. The penalty for a violation was a $25 fine. According to observations made at 33 middle schools just before the implementation of the law and again one year later, there was an increase in helmet use among young adolescents from about 20% during the pre-law period to 56% one year later. Because there was no comparison group, the increase in helmet use cannot necessarily be attributed to the helmet law. In a recent review, researchers in the field conclude that several studies suggest that helmet laws can encourage helmet use (Rivara, Thompson, Patterson, & Thompson, 1998). A review of the literature by researchers at the CDC also supports the assertion that legislation can be an effective helmet-promotion tool, especially when accompanied by an educational campaign (CDC, 1995). Overall, while the results described here are encouraging, further study will be needed to assess the relationship between helmet laws and helmet use among adolescents in particular.