Lane Use: Practice Questions & Explanations

The 'keep right except to pass' rule is the standard for multi-lane highway driving in every state. The right lane is for normal driving; left lanes are for passing. After completing a pass, return to the right or middle lane. Some states actively enforce left-lane camping with fines. The reason: lane discipline reduces lane-changing, and most multi-vehicle highway crashes involve lane changes. Slow vehicles in the left lane force faster vehicles to pass on the right, which is more dangerous than passing on the left. Always pass on the left when possible. On three-lane highways, the middle lane is for through traffic at the prevailing speed.

HOV lanes (also called 'carpool lanes' or 'diamond lanes' from the painted diamond markings) are restricted to vehicles with a specified minimum number of occupants — typically 2+ or 3+ depending on the road and time of day. The restriction usually applies during rush hours; outside posted hours the lane may be open to all traffic. HOV lanes are intended to encourage carpooling and reduce overall congestion. Some HOV lanes accept hybrid and electric vehicles regardless of occupancy under various clean-vehicle programs. Penalties for HOV violations are significant, often $300-$500 in many states. Diamond markings on the pavement and overhead signs identify HOV restrictions.

When your lane is ending (a 'lane drop'), the responsible behavior is to: identify the lane drop early (signs typically warn 1/2 mile and again 1/4 mile ahead); signal early; check for a gap in the adjacent lane; merge smoothly while there is still plenty of road remaining. The 'zipper merge' technique, where vehicles alternate from both lanes at the merge point, is encouraged in some states because it uses all available road space. Last-second forced merges create conflict and are a leading cause of low-speed collisions in construction zones and lane reductions. Plan ahead, do not race other drivers to the merge point.

A center left-turn lane — marked by a solid yellow outer line and a broken yellow inner line on each side, with left-turn arrows — is a shared lane in the middle of the road used only for making left turns or U-turns where permitted. Drivers from both directions use it to wait safely to turn left without blocking through traffic. It is not a passing lane, a through-travel lane, or a merging lane, and you should enter it only shortly before your turn. Misusing the center turn lane for travel or passing is dangerous and illegal. Understanding this special lane's purpose is part of lane-use rules of the road.

A high-occupancy vehicle (HOV) or carpool lane is reserved for vehicles carrying at least a posted minimum number of occupants (such as two or more people), and sometimes for other specifically permitted vehicles like buses, motorcycles, or qualifying clean-air vehicles, during the hours shown on the signs. HOV lanes encourage carpooling to reduce congestion. Entering or leaving the lane is typically allowed only at designated points, and crossing solid lines into the lane improperly is a violation. Using the HOV lane without meeting the occupancy requirement during restricted hours can bring a fine. Understanding HOV-lane rules is part of lane-use content.