For all the ambition of President Biden’s infrastructure proposal — massive spending boosts on trains and buses and a push to get Americans into electric cars — its priority for the nation’s road network is more basic: Fix them.

The Federal Highway Administration estimates a $435 billion backlog of rehabilitation needs, while an analysis of agency data by The Washington Post shows a fifth of the nation’s major roads, stretching almost 164,000 miles, were rated in poor condition in 2019. That figure has stayed mostly unchanged for a decade.

Yet more than a third of states’ capital spending on roads that year, $19 billion, went toward expanding the road network rather than chipping away at the backlog.

The hunger for new roads reflects a desire to connect growing communities and battle congestion at the local and state level in a nation where most people rely on cars. That appetite for expansion is clashing with new transportation priorities in Washington that seek to bolster existing highways while promoting other modes of travel.

Transportation experts say building more roads and highway lanes is environmentally unsustainable and does the opposite of what’s intended — adding to traffic levels over time rather than reducing congestion. Biden’s infrastructure proposal and a Democratic-led road-funding bill that would shape rules for federal aid to states are seeking to shift the focus to trains and bus networks, rather than personal vehicles.

‘We’re really good at building stuff’

Biden’s infrastructure plan, which would cost about $2 trillion, includes a $50 billion fund to improve 20,000 miles of streets and highways, making them safer for pedestrians and bicyclists while ensuring accessibility for wheelchair users. The plan proposes a similar approach for 10,000 bridges, backed by $40 billion.

Congressional Democrats working on renewal of a transportation funding bill to establish rules for aid to states say they want money directed toward fixing highways rather than adding new lanes. Rep. Peter A. DeFazio (D-Ore.), chairman of the House Transportation Committee, said state and local transportation departments have been biased too long in favor of highway expansion.

“There is a phenomenal amount of work that needs to go into just rebuilding what we have,” he said.

The push to accommodate growth is playing out across the country, particularly in areas seeing an influx of new residents. Political leaders and drivers often push for highway expansions, seeing them as the best way to speed commutes — a reason that’s often used to justify spending.

Matthew Hardy, program director for planning and performance management at the American Association of State Highway and Transportation Officials, said state leaders must balance paying off road project loans, maintaining current infrastructure and expanding capacity.

“They’ve got to take care of what they have, but there’s always this tension,” he said.

Some states already are prioritizing rehabilitation: Federal Highway Administration data analyzed by The Post shows 11 allocated less than a tenth of their road spending to expansion in 2019, the latest year for which data is available. Rhode Island spent nothing on new capacity as it pushes to address what a state official called a half-century of neglect to its roads. (D.C. also spent nothing on expanding road capacity.)

But eight other states allocated more than two-thirds of their spending to expansion. Among them is Washington state, where the transportation chief warned of an annual maintenance and preservation shortfall amounting to hundreds of millions of dollars.

Washington state officials say their experience illustrates the risks of pumping money into expanding roads and skimping on rehabilitation work. The Post’s analysis shows the state the eighth worst in the country for its share of roads in poor condition, at 27 percent. At the same time, more than three-fourths of the state’s spending on roads went toward expansion — fourth highest in the nation.

Roger Millar, the state’s transportation secretary, said his agency spends less than half of what’s needed to keep existing infrastructure in good condition and prevent costly deterioration — falling $925 million short every year. That includes maintenance, such as filling potholes, but also what he calls preservation, such as painting a bridge’s deck so the steel doesn’t rust. Meanwhile, billions of dollars’ worth of new roads and other projects are funded by a 2015 hike in the state gas tax.

“We’re perceived as builders of stuff, and we’re really good at building stuff,” Millar said. But upkeep has fallen short. “That’s a lot like putting a 20-year roof on your house, fully intending to replace it in 40 years. You know, your furniture is going to get wet.”

State Sen. Steve Hobbs, a Democrat who chairs the transportation committee, said Washington state has sought to tackle a maintenance backlog even as road funding has been squeezed by a drop-off in gas tax funds and ferry revenue. He said the mismatch between new road spending and unmet maintenance needs also is a function of the state’s growth.

New Census Bureau numbers show the state’s population grew 14.6 percent between 2010 and 2020, one of the fastest rates in the nation. But the consequences of forgoing maintenance can be dire, Hobbs said, pointing to the West Seattle High-Rise Bridge, a major corridor shut for safety in March 2020.

“Part of the problem you have is just the rapid population increase that’s happened over the last 10, 20 years and the need for infrastructure that matches that,” Hobbs said.

While Democrats want to prioritize federal aid to states seeking to improve the nation’s worst roads, Republicans say funding decisions are best left to state transportation officials. Justin Harclerode, a spokesman for Rep. Sam Graves (Mo.), the top Republican on the House Transportation Committee, said the need to maintain existing roads is clear, citing the recent closure of a bridge carrying Interstate 40 across the Mississippi River.

But, he added, Graves “doesn’t believe it’s a good idea to handcuff states by taking away the ability to add capacity, if that’s a critical need for them.”

Waiting on action in D.C.

Transportation for America, a policy organization that advocates for more spending on road maintenance, concluded in a 2019 report that many states were continuing to build new roads regardless of whether they could afford to maintain them. The problem compounds over time, according to the group, which estimated that each lane of new road adds $24,000 in annual maintenance costs per mile.

For decades, researchers have found that when roads get wider, people tend to drive more, ultimately canceling out any gains in speed. Susan Handy, a professor of environmental science and policy at the University of California at Davis, said traditional tools for forecasting traffic demand to assess the benefits of new construction don’t effectively take that into account.

Researchers noted that traffic eventually increases by about the same percentage a road is widened, so boosting the size of a road by 10 percent will lead to about 10 percent more travel. Handy was part of a team that developed a calculator to forecast that effect in California, and its use was recommended by the state transportation agency last year.

Handy said officials across the country need to consider other ways to tackle congestion, potentially through tolls and parking fees but especially by investing in alternatives such as mass transit. The Biden plan eschews new fees on drivers but does call for a $165 billion expansion in funding for rail and other transit.

Despite a push in the nation’s capital for multimodal transit options, state transportation funding across the country is heavily tilted in favor of cars. The tide has shifted in some states toward boosting the existing road network, mirroring the goals of the new administration.

In Mississippi, state transportation leaders decided a decade ago they couldn’t afford new roads and highway lanes, adopting a policy of dedicating money to preserving roads already in place.

“It was a better spending of our dollars,” said Jeffrey Altman, the state’s acting transportation director.

Mississippi ranks 11th from the bottom for the condition of its roads, with almost 27 percent rated as poor. It still spent 38 percent of its money on expansion in 2019 — but Altman said the state received federal grant money in recent years to back new construction.

Still, the focus is rehabilitation. Letting Mississippi roads deteriorate would drive up the costs to fix them in the long run, Altman said, and risk causing damage to vehicles. Altman said the state still faces a financial shortfall to repair roads but noted the legislature created a lottery in 2018 to provide up to $80 million in annual transportation funding — money that was plowed into maintenance.

In Rhode Island, which federal highway data indicates has the worst roads in the country — with half rated in poor condition — records indicate officials spent nothing on expansion in 2019.

Charles St. Martin, a spokesman for the state’s transportation department, said many of the worst roads are not under state control. But he said officials have worked since 2015 on a $5 billion campaign to address what he called “50 years of unprecedented neglect.”

“Expanding our state road system will not be a priority until the infrastructure is in a state of good repair,” he said.

Most states report the condition of their roads using the international roughness index, a measure of how many inches a vehicle’s suspension moves as it travels along a section of road. The bigger the moves, the higher the score and worse the condition.

Highway administration records have limitations. Millar said spending on a project that serves a rehabilitation goal while also boosting capacity could be classified as an expansion. And condition data counts only the length of roads, not how many lanes they have — which is important in determining how expensive they might be to fix.

Figures tracked for larger roads suggest the busiest are generally in better condition. Meanwhile, figures for minor local roads are not included in Federal Highway Administration data.

In Washington state, lawmakers are waiting to see what help they could receive from the federal government as infrastructure funding dominates debate in the other Washington.

Hobbs, the state transportation committee chairman, introduced in this year’s legislative session an $18 billion transportation funding package that included an infusion into road maintenance and preservation while limiting new construction to 15 percent of spending. The passage of that 16-year plan also is key to an ambitious carbon-pricing effort the legislature passed to address climate change by raising billions of dollars while reducing emissions.

The package was voted out of committee, but lawmakers decided they would pause to see how Biden’s infrastructure push fares, Hobbs said, “so we can layer on top of it.”