Final answer:
The purpose of a solid white line between lanes of traffic moving in the same direction is to indicate that it is unsafe for vehicles to change lanes. Motorists should not cross the solid line unless there is an emergency or if directed by a traffic control device.
Step-by-step explanation:
The purpose of a solid white line between lanes of traffic moving in the same direction is to indicate that it is unsafe for vehicles to change lanes. The solid white line is used to separate lanes and maintain the flow of traffic. Motorists should not cross the solid line unless there is an emergency or if directed by a traffic control device.
For example, on a multilane highway, a solid white line indicates that the lanes are moving in the same direction. Vehicles should stay within their lanes and not change lanes across the solid white line. This helps prevent accidents and ensures a smoother and safer flow of traffic.