<P> Overtaking (or passing) refers to a maneuver by which one or more vehicles traveling in the same direction are passed by another vehicle . On two - lane roads, when there is a split line or a dashed line on the side of the overtaker, drivers may overtake when it is safe . On multi-lane roads in most jurisdictions, overtaking is permitted in the "slower" lanes, though many require a special circumstance . See "Lanes" below . </P> <P> In the United Kingdom and Canada, notably on extra-urban roads, a solid white or yellow line closer to the driver is used to indicate that no overtaking is allowed in that lane . A double white or yellow line means that neither side may overtake . </P> <P> In the United States, a solid white line means that lane changes are discouraged and a double white line means that the lane change is prohibited . </P> <P> When a street is wide enough to accommodate several vehicles traveling side - by - side, it is usual for traffic to organize itself into lanes, that is, parallel corridors of traffic . Some roads have one lane for each direction of travel and others have multiple lanes for each direction . Most countries apply pavement markings to clearly indicate the limits of each lane and the direction of travel that it must be used for . In other countries lanes have no markings at all and drivers follow them mostly by intuition rather than visual stimulus . </P>

When do traffic engineers use signals in combination with signs and markings