State law says drivers should usually only travel in the left lane on the interstate when they’re passing other cars. But police have said that’s tough to enforce, in part because there’s an exception for when there’s no vehicle “directly behind” the left-lane driver. Sen. Jim Oberweis, a North Aurora Republican who also sponsored a 70 MPH speed-limit law back in 2013, tried to remove that exception this week with Senate Bill 991. But his fellow senators voiced several concerns …