In Mumbai, India, the trains are running again, but the bombing aftermath is scattered across the city: Loved ones looking for the missing, the injured lying in hospitals, funeral pyres burning for those killed.
The attacks sent shock waves to the United States, where security has been stepped up on trains and subways in many cities.
Every day, 32 million people take mass transit to work, to class, to sightsee. And the threat of terrorism has riders balancing fear with necessity.
"I mean, to be honest, I'm still scared to ride the trains since the terrorist stuff," says Chicago commuter Alicia Williams.
"You just gotta go to work and come home, or go do what you do and hope for the best and cross your fingers," says Dan Baker, another Chicago commuter.
On the country’s largest system, in New York, extra officers are patrolling and conducting more random bag checks. Those searches began last summer after the London subway bombings, creating some complaints and resignation.
Since then, cities are using other measures, like a surveillance system in Los Angeles. And in Washington today, an evacuation drill.
"Yesterday was a wake-up call that people need to know what to do in case of an emergency," says Charles Novick of the Washington Metropolitan Area Transit Authority.
But can all this really stop a bomber from targeting trains?
"We should not be mistaken to believe that cameras or any other one technology will protect the system," says NBC counterterrorism analyst Michael Sheehan. "The primary emphasis has to be on the investigations and to find and detect any cell that may be plotting against the system."
Last week, authorities announced that tactic stopped an alleged plot on the tunnels that run between New York and New Jersey. It also did something else — reminded folks of the threat.
Officials believe that's not necessarily a bad thing. While the objective is to get from point A to point B, riders should also be alert.
"I'm concerned there could be a similar situation to Madrid, London and Bombay, Mumbai," says Stewart Rubin, a Los Angeles commuter. "I've seen people get on the subway with some items they shouldn't have carried."
Millions of riders, living with a possible threat on a daily commute.