<P> The Bicycles May Use Full Lane Sign, also referred to as BMUFL or R4 - 11, first officially specified in Chapter 9B of the 2009 Manual on Uniform Traffic Control Devices, is a traffic sign used in the United States to: </P> <Ul> <Li> designate roads with lanes that are too narrow to be safely shared side - by - side by a bicycle and another vehicle to indicate that bicyclists may occupy the full lane to discourage unsafe within - lane passing </Li> <Li> encourage bicyclists to use the full lane to discourage unsafe within - lane passing </Li> <Li> encourage motorists to change lanes to pass bicyclists </Li> <Li> warn motorists that bicyclists may be using the full lane </Li> </Ul>

When is a bicyclist or motorcyclist entitled to a full lane