With the American Automobile Association predicting that 50.9 million Americans will travel during the Thanksgiving holiday this week—a 3.3 percent increase over 2016—it seems people are in the mood to travel.

The challenge becomes keeping a good mood for the long haul should traffic slow down to a grind and the costs add up.

“Last year, congestion cost each U.S. driver $1,400 on average, for a total of nearly $300 billion, according to Inrix’s latest annual scorecard,” The Wall Street Journal reported. “The cost reflects wasted fuel, decreased productivity and lost time…The biggest losers are the most congested cities.”

Among those bottleneck cities are Boston, New York, Chicago, Los Angeles, and Austin.

A commonly reported issue that tends to clog-up highways is failing to keep up with the flow of traffic.

Some experts believe that driving too slowly in the passing lane is at least as dangerous as driving too fast because people trapped from behind get frustrated and make dangerous maneuvers, creating anger and accidents.

Most states already have laws stipulating that the left lane is for passing or turning left, not for cruising. Georgia, Tennessee, Virginia, Nevada and Oklahoma are among states with new laws increasing fines and are ratcheting up enforcement.

As far as Derek Stagner is concerned, any crackdown is long overdue. Mr. Stagner, 46, commutes 10 miles every day to his job at a downtown St. Louis creative firm, and frequently gets caught behind slow-moving drivers in the left lane.

“Why has no one ever told them this is not what you should do?” Mr. Stagner asked. “I think it creates road rage. People get upset and then it becomes combative.”

State legislatures increasingly agree.

Oklahoma’s law, which recently took effect and requires drivers to stay to the right unless passing or preparing to turn left, carries fines of more than $200 for left lane dawdlers.

“I believe it has caused some road rage incidents,” said Trooper Dwight Durant, a spokesman for the Oklahoma Highway Patrol. “It’s caused some collisions with property damage, personal injury and even death. We’re hopeful this new law will cut down on that.”

Similar laws that took effect July 1 in Virginia and Nevada carry fines of up to $250 for left lane hogs, and several other states are considering similar measures.

Other states are trying a gentler approach.

The Missouri Department of Transportation typically uses its 280 electronic highway message boards to warn motorists of wrecks up ahead or slippery conditions. But the messages also include public service notices about buckling up, putting down the cellphone and driving in the proper lane.

“Camp in the Ozarks, not the left lane,” one recent message read.

This article contains information from The Associated Press.