Adults bicyclists in California would all have to wear helmets under a bill from state Sen. Carol Liu (D-La Cañada Flintridge). If passed, California would become the only state with a mandatory helmet law for riders 18 and older.

The bill would also require adults to wear reflective clothing at night, and it calls for anyone under 18 to wear a mandatory helmet while skateboarding or rollerskating.

The fine for a violation would be $25.

Since 1994, California has required bike helmets for children and teens under 18. All told, 21 states and the District of Columbia require helmets for youth bicyclists.

"Any responsible bicycle rider should wear a helmet,” Liu said in a statement last week announcing the adult helmet legislation.