A growing number of Americans are getting stuck in traffic jams, unable to find parking and driving on roads that aren’t safe, the head of the National Highway Traffic Safety Administration says.

The problem has been exacerbated by a surge in new car ownership, fueled in part by a growing supply of high-occupancy vehicle (HOV) lanes on the nation’s roads.

HOV lanes are intended to encourage people to use them, reducing traffic congestion.

But in the past few years, the number of HOV-lane-compliant cars on the roads has skyrocketed.

A study published in July by the National Transportation Safety Board (NTSB) found that drivers were responsible for more than a third of all crashes involving people using HOV lane violations, a rate that rose to more than 40 percent of all fatalities in 2016.

That’s despite drivers in some states requiring new HOV access.

California, Oregon, Washington and Minnesota all passed laws last year requiring cars to have at least two HOV exits available in each lane, a policy called “double-parking.”

The NHTSA issued a report last year that found HOV drivers accounted for nearly one-third of all HOV crashes, with many people still confused by the new rules.

The NSTB also said the number and type of HOC lanes have increased over the past decade.

But it said the numbers of HOBs has also gone up significantly, as have the number drivers using them.

The agency said it’s trying to make sure it doesn’t “get ahead of the curve.”

The agency is studying how to address this problem, but said it doesn, too.

It said its goal is to encourage all HOC-lane users to use the lane, but to avoid creating new traffic patterns.

The agency also wants to see states and cities implement more traffic-calming measures, like “double locking” and “bicycle lockdowns.”

It said those types of measures, which use both drivers and other traffic control devices, should help improve safety on the roadways, but it isn’t yet clear if they will.

“If we can prevent crashes by making it safer for drivers, we can reduce crashes by increasing safety for all,” NSTb Chair Deborah Gellos said in a statement.