The Casey Overpass undergoes its second day of demolition, on Tuesday, May 19, 2015.

WASHINGTON – Nearly 235,000, or some 38 percent of all U.S. bridges, need repair, replacement or major rehab, according to an analysis of federal data by the American Road & Transportation Builders Association.

The association combed through the Department of Transportation 2018 Bridge Inventory database to find that the number of structurally deficient bridges — those considered to be in poor condition according to the Federal Highway Administration — dropped just 1 percent from 2017, to 47,052 out of a total of 616,087 U.S. bridges. But the pace of improvement has slowed to the lowest point since the group began doing this analysis five years ago.

"The total inventory of structurally deficient bridges is down by about 567, which is a very slow pace compared to what we've seen in previous years," said Alison Premo Black, the association's chief economist who conducted the analysis. "At that pace, it would take over 80 years to repair or replace those bridges, which is just a ridiculously long time."

ARTBA's primary goal is to aggressively grow and protect transportation infrastructure investment. Many of its 8,000 members stand to benefit from increased funding.

The association estimates it will cost nearly $171 billion to repair all the bridges currently identified as deficient.

Infrastructure has been a bipartisan issue, with President Donald Trump and Democrats running for president calling for new investments. On Friday, the president visited the Lake Okeechobee to tout work on a water management project near his Palm Beach Mar-a-Lago resort.

Finding a way to pay for infrastructure projects has been a major obstacle, with federal spending on the decline. From 2003 to 2017, adjusted for inflation, there has been a 20 percent decrease in federal spending on transportation and water infrastructure, according to the Congressional Budget Office.

"Incoming revenues are not anywhere where they need to be to make all of the needed investments to keep things in a good state of repair and make some of these larger replacement and rehabilitation projects happen," Black said.

Federal money for road and bridge projects comes from the Highway Trust Fund, which receives money from a federal gas tax of 18.4 cents per gallon and 24.4 cents per gallon of diesel fuel. The federal tax hasn't been raised since 1993, although more than two dozen states have increased taxes in that time.

Democratic presidential candidate Amy Klobuchar has made infrastructure a focus of her campaign. The Minnesota senator announced her candidacy with the backdrop of the rebuilt I-35W bridge, which collapsed in 2007, killing 13 people and injuring 145.

She has countered Trump's $1 trillion infrastructure plan with one of her own, outlining a program that would raise the corporate tax rate from 21 to 25 percent and leverage federal funding through bond programs and clean-energy incentives.

The U.S. Chamber of Commerce has called for an increase in the gas tax by 25 cents a gallon, jumping 5 cents each year over five years, to pay for infrastructure projects.

"There is no magical way for the government to pay for infrastructure without collecting the money from someone first. And the fairest thing to do is to collect it from the users of that infrastructure," Tom Donohue, president and CEO of the U.S. Chamber of Commerce, told lawmakers in March.