The American Society of Civil Engineers recently issued a report card giving Maine's transportation infrastructure a grade of C-minus. The poor condition of our state's roads and bridges ends up costing Maine drivers, on average, an extra $299 a year in car repairs. As this report card concluded, "the health, safety and welfare of our citizens are directly tied to the quality of our infrastructure."

According to the Federal Highway Administration (FHWA), 32 percent of Maine's bridges are deficient, which is more than the national average of 25 percent. There are nearly 800 deficient bridges in Maine. The Maine Department of Transportation (DOT) estimates that its annual required investment to maintain good repair for our highways and bridges would cost $355 million, which is $110 million above the amount the state is able to spend.

Being classified as deficient doesn't mean a bridge is going to fall down anytime soon. But it does signify that the bridge needs serious rehabilitation. The terrifying bridge collapse that occurred recently in Washington state magnifies the importance of properly maintaining our nation's highways and bridges.

Our national highway system contains too much infrastructure that is now well past its useful life. Some bridges are more than 100 years old; many are unable to accommodate today's traffic volumes. In fact, one in nine of the nation's bridges is rated as structurally deficient; and of the total 607,000 bridges in our country, the average age is 42 years old.

The FHWA estimates that we must invest more than $101 billion at all levels of government each year just to maintain our highways and bridges over the next 15 years. Improving the system to meet future demands will require $170 billion each year. This will prove difficult given that revenues collected for the Highway Trust Fund already do not support the current level of spending.

The math is clear: the Trust Fund collected $40 billion in revenue last year, but spent close to $50 billion. This is not a new problem; there has been a shortfall every year for the past five years.

By the end of next year, Congress will have transferred nearly $54 billion in General Funds into the Highway Trust Fund in order to ensure its solvency. In order for states and localities to plan and build long-term projects, they must have guaranteed funding to support the critical infrastructure investments.

Transportation is one of the largest sectors of the U.S. economy, representing nearly 10 percent of the nation's gross domestic product, and it's one of the largest generators of good-paying jobs. Improving the efficiency and reliability of the nation's transportation system is vital to the movement of freight and people and is critical to our economy.

I serve as the Ranking Member of the Senate Transportation Appropriations Subcommittee. Our committee recently held a hearing to draw attention to our outdated and overburdened highways and bridges, and the need to make long-term investments in programs that will help fix them.

I am a strong advocate of one of these programs, the Transportation Investment Generating Economic Recovery, or TIGER, grants program. I have supported Maine DOT's successful efforts to obtain $20 million to replace the Memorial Bridge linking Maine and New Hampshire. The new Memorial Bridge is set to open this summer.

In addition, I have secured $10.8 million to replace the bridge between Richmond and Dresden, and more than $5 million to replace the aging Martin Memorial Bridge in Rumford. All of these bridges were past their expected lives and needed replacement, like so many other bridges across our nation. I continue to advocate for additional TIGER funding for several other infrastructure projects around Maine.

It's clear that additional investments are necessary. While President Barack Obama has requested $50 billion in immediate transportation investments to spur economic investment and rebuild America, I am disappointed that this was not supported with a serious proposal to finance it.

I do, however, share the Administration's belief that investment in transportation is critical to our economy. We must work together to find fiscally responsible solutions. Such investments create jobs, provide lasting assets, move commerce and pave the way for a better economic future.