I was half expecting to spend the day in the back seat of a humvee, being chauffeured around the base for various photo ops, but to my delight the Major in the charge of the course had other plans. We hoofed miles and miles and miles through the thick Quantico forest, crossed streams, and logged many hours on the base's blacktop roads on one of the hottest days of the summer to give us just a small taste of what the Marines on the other end of my camera were going through.

To protect the integrity and efficacy of the training for future officer classes, the Marine Corps asked that some events not be photographed and that the timeline be obscured when describing the Combat Endurance Test. For this same reason I won't say how long the test lasted, but I will say this was both mentally and physically the toughest assignment I've ever shot. I have a newfound respect for our Marine Infantry Officers and the men who train them.

Marine 2nd Lieutenants muster before beginning the Combat Endurance Test. The CET is the first test of the Infantry Officer Course at Marine Corps Base Quantico in Quantico, Va. Luke Sharrett for The New York Times.

The story focused on the need for infrastructure improvements on Amtrak's dedicated passenger service rail line known as the Northeast Corridor. Stretching from Washington, D.C. to Boston, Mass., Amtrak owns the 100-year-old electrified right-of-way that was originally built by the great Pennsylvania Railroad during the golden age of railroading at the turn of the century. That age has come and gone, leaving behind a slew of deteriorating majestic steel bridges and stone-lined tunnels. It's this aging infrastructure that hamstrings Amtrak's high-speed Acela Express trains, allowing them to reach their top speed of 150 mph at only one segment in Rhode Island on the entire corridor.

New Jersey Transit commuter trains emerge (Left) and enter (Right) the Hudson River Tunnel underneath Madison Square Garden in Penn Station on Monday, August 6, 2012. The tunnel has reached it's operating capacity with 24 trains traveling through it's Southern bore every hour during the morning rush. Luke Sharrett for The New York Times.