Question This sign means: Answers Trucks are permitted on an upcoming narrow bridge. The bridge ahead is open to one-way traffic only. The bridge ahead is wide enough for only one car at a time. The bridge ahead may be too narrow to meet or pass a truck. Explanation Warning signs are used to warn drivers about upcoming hazardous conditions and are usually yellow with black markings. This sign warns drivers that an upcoming bridge may be too narrow to meet or pass a truck and that they should be careful.