In a rare move for an agency better known for investigating crashes, the National Transportation Safety Board warned lawmakers Tuesday not to sacrifice public safety as they seek to cut government spending.

Cutting corners on investment in infrastructure built to last for decades will have long-term consequences, the NTSB said as Congress and the Obama administration ponder ways to tame spending and avoid automatic cuts set to take place next year.

NTSB Chairman Deborah A.P. Hersman said that as negotiators look for ways to trim the federal budget, “safety needs to have a seat at the table.”

“As they’re taking on these tough issues, they also need to recognize that there is a safety investment in doing some of these things,” she said, “and it can result in lives saved, injuries prevented and driving accident levels down.”

The NTSB has added infrastructure investment to its most-wanted list, an annual compilation of priorities intended to draw public attention to the issues.

Traditionally, the list has been more narrowly focused on concerns such as motorcycle or bus safety, teenage drivers and airport runway safety. But under Hersman’s leadership, the list has expanded to include more-general factors, such as the role that fatigue and distraction play in accidents. Now, the need to rebuild roads, bridges, pipelines and the air-travel system has a place among the NTSB’s top concerns.

“The thing with safety and infrastructure is that people don’t really think about it having a seat at the table until something catastrophic happens,” Hersman said. “We’ve got to make sure that safety is a part of the dialogue. When you think about how long some of these assets are around, we may think they’re going to be around 10, 20, 30 years, but in reality they’re around 50 to maybe 100 years.”

Although long concerned about the safety implications of deteriorating roads and bridges that have outlived their life span, Hersman said she and other NTSB board members were particularly struck by a Washington Post report on an analysis by Standard & Poor’s Ratings Services. It said Washington’s failure to find money to repair the nation’s transportation system was likely to shift the cost of critical infrastructure repairs to state and local taxpayers.

And, the S&P report underscored, “some important construction could simply be deferred.”

Earlier studies have sought to put a price on rebuilding systems constructed in the aftermath of World War II, although some date to the 19th century.

“Half of the bridges in this country were built before 1964,” Hersman said, and 70,000 bridges have been graded structurally deficient.

Tens of thousands of miles of highway that for decades have been repaved need to be dug up and rebuilt from the bare earth. In addition to billions of dollars for road and bridge replacement, U.S. ports need an overhaul estimated at $30 billion if they are to stay competitive in a global marketplace, experts say.

The American Society of Civil Engineers estimates the cost of resurrecting a patchwork electrical grid at $107 billion by 2020.

With about 25 percent of the nation’s drinking water thought to be leaking from pipes, the cost of fixing that system has been estimated at $335 billion. To fix sewer systems, add $300 billion.

A highly regarded study on the subject, done two years ago by a group co-chaired by former transportation secretaries Norman Y. Mineta and Samuel K. Skinner, estimated that an additional $134 billion to $262 billion should be spent on infrastructure per year.

If a cash-strapped Congress postpones dealing with infrastructure needs or punts to state legislatures, Hersman said, the result may be Band-Aid measures that put lives at risk.

“This is an opportunity in advance of the legislative sessions both at the state and the federal level to outline some priorities,” she said.