The next time you’re driving on Pennsylvania Avenue in Northwest Washington and think about making a U-turn across the road’s bike lanes, remember that it could cost you. 

Mayor Vincent C. Gray (D) announced an emergency rule this week, banning illegal U-turns across bike lanes even if no bicycle riders are present. The rule, which goes into effect Dec. 1, applies to one roadway so far: Pennsylvania Avenue NW, which is the only road in the District with center bike lanes.

According to the the mayor’s office, 11 of the 14 bike crashes on Pennsylvania Avenue in 2010 and 2011 involved vehicles making U-turns. The Washington Area Bicyclist Association campaigned to have U-turns across bike lanes banned. 

Once the rule goes into effect, an illegal U-turn across bike lanes could result in a $100 fine. 

The Pennsylvania Avenue lanes opened in 2010. New bike lanes on L Street NW, which have sown confusion recently for drivers, are the latest addition to the District’s roads. Planners hope the network of bike lanes will eventually include 80 miles of dedicated lanes.