JEFFERSON CITY, Mo. (AP) — THE ISSUE: The U.S. interstate highway system, celebrating its 60th birthday this year, is showing its age. Many roads and bridges are in need of repair or expansion. Similar problems exist for public drinking and wastewater systems, dams and levees, airports, railroads and mass transit systems. Politicians generally agree the nation's infrastructure is in need of improvement. Deciding how to pay for it and which projects should take priority is more difficult.

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WHERE THEY STAND

To hear either candidate talk, a staggering amount of money is going to be spent on infrastructure — if Congress goes along.

Democrat Hillary Clinton has proposed spending $250 billion over the next five years on infrastructure. She proposes to repair and improve roads and bridges, expand public transit, make affordable high-speed internet access available to all households by 2020 and modernize passenger rail systems, airports, dams, levees and wastewater systems. Clinton also proposes to direct $25 billion over five years to a new national infrastructure bank, which she said could support about $225 billion in loans for local infrastructure projects. A similar lending bank was proposed by President Barack Obama during his first term but failed to win congressional approval.

Republican Donald Trump has said he wants to spend at least double the amount Clinton has proposed for infrastructure, financed through low-interest bonds. His campaign said a more detailed plan is coming. In his 2015 book, "Crippled America: How to Make America Great Again," Trump said a large-scale public infrastructure plan could create the "biggest economic boom in this country since the New Deal," a series of programs started in the 1930s by President Franklin Roosevelt.

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WHY IT MATTERS

A reliable infrastructure system strengthens the nation's economy, enhances public safety and can improve the quality of life.

Public health can be put at risk by poor infrastructure, such as when lead-tainted pipes contaminated the water supply of Flint, Michigan.

Commerce depends on the safe and efficient shipment of goods via air, rail, water and roads from manufacturers to retailers and homes. Poor infrastructure and traffic congestion can raise the cost of doing business, making products more expensive for consumers.

A long, slow commute due to inadequate capacity on roads or public transit can put an emotional strain on families. It can make the difference whether parents arrive on time for a family dinner or a child's concert or soccer game.

According to a report last year by the Congressional Budget Office, the share of gross domestic product generated by government spending on public transportation and water infrastructure peaked in 1959. Spending on such projects fell by 5 percent from 2003 to 2014 when measured as a percentage of GDP, with highway spending leading the decline.

Officials have taken some steps to try to reverse that. Congress broke a political logjam last year by passing a five-year, $305 billion transportation plan. More than half the states also have acted since 2013 to boost transportation spending through higher taxes, fees and borrowing.

Yet the needs remain great. About 20 percent of the nation's 900,000 miles of interstates and major roads needs resurfacing or reconstruction, according to one analysis. A quarter of the 600,000 bridges are considered structurally deficient or functionally obsolete.

In a report earlier this year, the American Society of Civil Engineers projected the U.S. will face a funding gap of more than $1.4 trillion by 2025 for its roads and bridges, drinking and wastewater systems, electrical infrastructure, aviation and water ports.