With record numbers of travelers set to hit the highways and byways of America this holiday weekend, it sounds like it’ll be quite a party out there on those roads. But according to a new report, it’s this kind of increased travel that’s putting a strain on the nation’s 60-year-old interstate highway system, causing congestion while needed repairs stack up.

A report from research group TRIP [PDF] that looked at Federal Highway Administration figures, timed to the 60th anniversary of the interstate highway system on June 29, notes that while the system only has about 2.5% of the miles of lanes nationwide, it carries 25% of traffic. Traffic has grown at twice the rate of new lanes since 2000, the report found, which has led to congestion.

Of the country’s urban interstates, about 43% are considered congested because traffic has significant delays during peak hours, FHA figures show.

Then there’s the estimated $189 billion backlog of needed improvements, according to the Transportation Department, which includes $100 billion for expansion and enhancement, $59 billion to fix up pavement, and $30 billion to restore bridges.

“Drivers are frustrated with the condition of the nation’s transportation system,” Jill Ingrassia, AAA’s director of government relations told USA Today. “While a record 36 million travelers plan to hit the road for Independence Day weekend, nearly 70% are concerned that roads and bridges are not in great driving condition.”

Many travelers will experience those crowded interstates over the Fourth of July holiday, AAA says, due to gas hitting its lowest prices since 2005: a projected 36.3 million people will drive 50 miles or more from home during the holiday period, up 1.2% from last year.

“Spurred by the lowest gas prices since 2005, more people than ever are planning to travel this Independence Day weekend,” said Marshall Doney, AAA president and CEO. “We are well on our way for 2016 to be a record-breaking year for summertime travel.”

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