‘I will survive.”

That’s what a straphanger wrote on the fogged-up windows of a hot, dark and crowded F train Monday evening, as other passengers stripped off clothing and tried to pry windows open to get air.

Everyone did survive the nightmare on the subway tracks that left them in a train that stopped underground between stops in lower Manhattan because it lost power. Riders were stranded without lights or air conditioning for 45 minutes. But the horrific situation has to become a turning point in the subway’s ongoing troubles.

Monday night, the problems underground went from being annoying to dangerous. It’s no longer about being late to work, or waiting for a train. It’s now about the safety of the system, and the health of its riders.

Where’s the urgency? Where’s the outrage? Where’s Gov. Andrew Cuomo, who said nothing in the wake of Monday’s incident? A spokesman for Mayor Bill de Blasio, called the incident “an unacceptable failure,” and blamed the MTA. That doesn’t go far enough, either.

The incident highlighted numerous problems. The old trains and their power problems are, of course, at the top of the list. But there’s more. Riders said they were first told they stopped due to train traffic ahead. MTA officials couldn’t confirm that, but the need for better communication is clear. Then, there’s the question of what happened once the train restarted. An MTA spokesman said that because it first went too far into the station, the doors wouldn’t automatically open, forcing passengers to wait even longer for their escape. And questions remain as to whether there was an alternative response that would’ve gotten passengers off the train more quickly, and whether there were medical personnel on the platform to help those in need. They need to be answered.

This should be the moment when the governor, the mayor and top MTA officials step up, recognize the severity of the problem, and work together to find immediate solutions to deal with the dangers of a dilapidated system. Commuting to work, and home again, shouldn’t be a hazard to anyone’s health.