How to fund America’s crumbling infrastructure has been a recurring theme in the 2016 presidential election, but the most obvious (and irritating) sign of that is already costing taxpayers.

Pothole damage has cost U.S. drivers $15 billion in vehicle repairs over the last five years, or approximately $3 billion annually, a new study from the American Automobile Association concluded. With two-thirds of Americans concerned about potholes on local roadways, according to the study, the organization cautions drivers to remain on high alert to potholes on their regular routes — often easier said than done — and urges state and local governments to fully fund and prioritize road maintenance.

On average, American drivers report paying $300 to repair pothole-related vehicle damage, the study found. And they appeared to live in areas where potholes were hard to avoid: Those whose vehicles incurred this type of damage had that happen an average of three times in the last five years. “In the last five years, 16 million drivers across the country have suffered pothole damage to their vehicles,” John Nielsen, AAA’s managing director of automotive engineering and repair, said in a statement. “The problems range from tire punctures and bent wheels, to more expensive suspension damage.”

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Last year, Congress passed a five-year infrastructure bill to provide $305 billion to repair roads, bridges and rail lines. President Obama originally proposed $478 billion funding for roads, bridges and rail projects funded by a one-off 14% transition tax on untaxed foreign earnings that U.S. companies have already made overseas. Some $170 billion in additional funding is needed per year to improve roads and bridges, Nielsen said. Nine states are currently having debates about hiking their “gas tax,” according to Citizens for Tax Justice, a nonprofit group focusing on tax policy.

Presidential candidates Sen. Ted Cruz (R., Texas) and Sen. Marco Rubio (R., Fla.) both voted against the so-called highway bill, but Republican frontrunner Donald Trump has perhaps been one of the most vocal on the subject. “We’ve spent $4 trillion trying to topple various people that frankly — if we could’ve spent that $4 trillion in the United States to fix our roads, our bridges, and all of the other problems; our airports and all of the other problems we’ve had —we would’ve been a lot better off,” Trump said in a debate last December.

The Democratic presidential candidates have also vowed to boost federal investment on infrastructure. Hillary Clinton has pledged $275 billion over the next five years, should she win the White House, and her rival for the nomination, Bernie Sanders, has also said nearly a quarter of the nation’s 600,000 bridges have been designated as structurally deficient or functionally obsolete. Some 32% of roads are in poor or mediocre condition, which costs every motorist the equivalent of $324 a year, Sanders said, citing a report by the American Society of Civil Engineers.