ARLINGTON, Va.—It’s not the first time drivers might experience shuttered pumps at gas stations, but the reason has nothing to do with natural disasters or low supplies. It’s a shortage of drivers to deliver the fuel to gas stations, NBC News reports.

The National Tank Truck Carriers estimates that a quarter of U.S. tanker trucks have been parked because no one’s available to get behind the wheel.

“Trucking’s driver shortage already exceeds 50,000 drivers,” wrote the trade group. “The trucking industry’s workforce shortage is not confined to drivers alone. … Trucking companies also require dispatchers and back-office staff. Trained mechanics are also in short supply. Tank truck operations face further critical shortages of registered inspectors and design-certified engineers who can inspect and repair cargo tank truck trailers.”

With the pandemic easing and more people hitting the road for work or vacation, gas prices have been climbing, with the average now reaching $2.88 per gallon, according to AAA. Fuel shortages have already been seen in Arizona, Florida and Missouri because of lack of tank truck drivers—a concern as the busier summer travel time inches closer.

The truck driver shortfall has been growing in recent years, as older drivers retire and new ones haven’t lined up to replace them. The long hours and pay scale of a trucker hasn’t made it an attractive career opportunity for younger workers, according to the American Trucking Association (ATA), which predicted there will be a “significant tightening of the driver market.”

The other complication has been that drivers licensed to pull an 18-wheeler aren’t licensed to operate a tank truck, which requires more certification related to the fuel. The federal registry that identifies drivers with drugs or alcohol issues debuted in early 2020, further culling the ranks of eligible drivers.

NACS and other industry trade groups recently asked the Federal Motor Carrier Safety Administration (FMCSA) to issue another national waiver exempting truck drivers transporting fuel from hours-of-service rules. A two-part NACS Daily series recently examined the truck driver shortage. Read “Trucker Shortage Hits Home” and “Higher Pay for the Long Haul.”