I am a loyal Amtrak rider. And I am proud of it. That's why I am pleased to see that, in spite of great initial fears, the Infrastructure Renewal Program underway at New York City's Penn Station has been going smoothly.

The Renewal Program consists of Amtrak removing the equivalent of six football fields' worth of track and installing new track and switches all before Labor Day. That's no small feat. The mere thought of it — and the possible disruption that some thought would occur — caused New York Gov. Andrew Cuomo to dub it "the Summer of Hell." I am pleased to see that several weeks into the program, the governor's prediction has not come true, thanks in large part to the planning by Amtrak in conjunction with Long Island Railroad and New Jersey Transit.

As a former mayor of Philadelphia this comes as no surprise to me. I have watched Wick Moorman, who came on board less than a year ago as CEO, make real changes at Amtrak — streamlining operations, emphasizing a culture of safety and reliability, and working to enhance the customer experience. I have no doubt that further positive changes will occur with Richard Anderson joining Moorman in leading Amtrak. Yet, while Amtrak is making real change, the greatest threat it faces is a failure of our nation's leaders to invest in its critical infrastructure and to help improve and maintain its assets.

In terms of infrastructure, Amtrak is no different from the country as a whole. In fact, Amtrak may be a leading indicator of the kind of investment and focus on renewal that is required in order for our country to realize its potential overall.

When running a railroad, you can't be responsive to the needs of your passengers if you don't have dependable equipment to get them where they need to go. Without resources, Amtrak trains will be forced to continue to travel on decades-old tracks and through tunnels that are more than 100 years old.

At the National Press Club in July, Moorman said we are at a critical crossroads in our nation when facing our infrastructure challenges. In rail, we can either invest in upgrade that make travel safer and more reliable, or do nothing and put passengers at risk.

To me, as a frequent Amtrak rider, the choice is clear. Rail travel is a part of every day life for millions of Americans. We should be building it up, not watching it fall apart.

Decades of insufficient funding — doing nothing or doing just enough to get by — has brought the country's infrastructure to a breaking point. The 2017 Society of Civil Engineers study gave the state of U.S. infrastructure a "D plus." That is shameful and disturbing. None of us would be proud of a "D plus" in our own work product. This kind of grade says an enormous amount about our country's priorities.

When it comes to passenger rail travel, Amtrak is doing everything it can to maintain and upgrade its infrastructure with the resources it has. But, as a former chair of Amtrak's Mayor's Advisory Council, I know that they can't do it alone. Congress and the new administration must understand that rail infrastructure investments not only help Amtrak better serve Americans and our international visitors, but also stimulate job growth in construction, manufacturing, and professional services. Investments in these sectors can help spur the rebirth of America's passenger rail, manufacturing, and supply sectors, which has been largely dormant and overtaken by international firms.

We are learning many lessons this summer from Amtrak. Perhaps the most important one is that the clock is ticking on the deteriorating state of our infrastructure. Thankfully, this has not been the "Summer of Hell," as some predicted. Instead, I believe it will be seen as a "Summer of Enlightenment" for our country's leaders on the importance of investing in infrastructure.

Michael A. Nutter is the former mayor of Philadelphia, and past president of the U.S. Conference of Mayors. @michael_nutter