All states allow drivers to use the left lane (when there is more than one in the same direction) to pass. Most states restrict use of the left lane by slow-moving traffic that is not passing. A few states restrict the left lane only for passing or turning left. Some states have “yield laws” which require drivers to move into the right-hand lane if they are blocking traffic in the left lane. Most states follow the Uniform Vehicle Code and require drivers to keep right if they are going slower than the normal speed of traffic (regardless of the speed limit). A handful of states either do not require vehicles to keep right or permit vehicles moving at the speed limit to drive in the left lane regardless of traffic conditions.

All states have “Keep Right Laws” which require vehicles travelling slower than the normal speed of traffic (defined differently in each state) to travel in the furthest right lane. A growing number of states, however, designate the far-left lane as a “passing only” lane, making it illegal to travel in that lane other than to pass another vehicle. Driving in the left lane for anything other than passing is not only illegal in a growing number of states, its unsafe and results in thousands of accidents annually, according to a study by the Traffic Operations & Safety Laboratory within the engineering department of the University of Wisconsin-Madison. When looking for deeper pockets or additional defendants in automobile collision litigation, don’t look past the driver who may have put the entire sequence of events into action. If a driver is parked in the left lane on a four-lane highway and is not passing someone or making a left turn, he or she is breaking the law in a majority of states and can be ticketed.
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There are two types of drivers: (1) those who get upset when somebody is illegally hanging out in the left passing lane, and (2) those who are blissfully ignorant that hanging out in the passing lane is both illegal and dangerous. When slower drivers are scattered between the right and left lanes, faster drivers must weave back and forth, slowing and speeding up repeatedly. For those who believe that they shouldn’t have to move over if they’re driving the posted speed limit, not only are they driving illegally, but evidence shows that slowing down and changing lanes is more dangerous than speeding. A car going 5 MPH slower than the speed limit has a greater chance of causing an accident than one going 5 MPH faster than the speed limit. That is why every state has some law on the books restricting the use of the left passing lane.

In 29 states, any car traveling slower than surrounding traffic must be in the right lane. In 11 states, the laws are even stricter—reserving the left lane only for turning or passing. In a growing number of states—especially Texas, Washington, and Ohio—police are engaging in an aggressive program to ticket violators. In Germany, the autobahn has a lower accident rate than American highways, despite there being no speed limit. The reason for this is that German drivers stay to the right unless they are passing.


https://www.mwl-law.com/wp-content/uploads/2018/05/SLOWER-TRAFFIC-KEEP-RIGHT.pdf