- White lane markings separate lanes of traffic travelling in the same direction, or shoulder boundaries.
- Crossing a single, solid white line is discouraged.
- Crossing double white lines is prohibited.
- Yellow lane markings are used to identify lanes of traffic travelling in opposite direction.
- Broken lines mean that you are permitted to change lanes or pass when it is safe to do so.
- Crossing double yellow lines is prohibited.
When safe to do so, and permitted in your state, crossing solid lines is permitted when turning into driveways.
Passing two directions
Two-lane, two-way roadway: Passing is permitted when safe to do so. Do not try to pass on a hill or on a blind curve.
Two-lane, two-way roadway: Passing is prohibited from both directions. Crossing the centerline is permitted only to turn into driveways, when permitted in your state.
Passing one direction
Two-lane, two-way roadway: Passing prohibited when the solid yellow line is in your lane.
Multilane, two-way roadway: Crossing the centerline is permitted only to turn into driveways.
Center two-way left turn lane
Multilane, two-way roadway, with two-way left turn lane: This is reserved only for left-turning vehicles in either direction. Special signs and pavement marking arrows are used.
Multilane, two-way roadway, with special lanes assigned to buses and carpools. Diamond markings for high occupancy vehicles (HOV) and special signs are visible. The double white line indicates that changing lanes at this point is prohibited.
Reversible traffic lanes are usually used to increase traffic flow into and out of the city. Some roadways may have special rules or restrictions during certain early morning and evening hours. These restrictions are often used in large urban areas to improve traffic flow during commuting hours and can include reversing the direction of travel for a lane or road and allowing the use of the shoulder as a travel lane. It is important to know the local traffic restrictions in areas where you plan to drive.