In the wake of several high profile subway shoving tragedies, it was announced that the MTA will reconsider installing sliding doors on some subway platforms. But considering that this issue has been brought up several times over the last few years (often after high profile subway deaths), it's hard to tell how serious, or feasible, an idea it actually is. We spoke to transit architect Jonathan Cohn, the design director of the JFK AirTrain, about the plan: "I totally think it's way past due, they really need to do it," he told us. "But I can understand they have their constraints and funding issues. It's going to take some serious leadership to get it going."

Cohn, who works for Perkins Eastman, noted that he is quite familiar with the idea: he previously worked on a proposal to add sliding doors to the Second Avenue Subway in 2007. "I was really excited about it, just coming off of the JFK AirTrain," he said. "I thought we had great qualifications to do the study and implement them. In the end, they decided not to proceed with it, but that was a great opportunity for NYC Transit to do it."

He said there were two major factors getting in the way of the MTA implementing any plan: putting in sliding doors limits their ability to run different vehicles (which have different geometric configurations) on the tracks; and it's quite costly. In terms of the first problem, Cohn said there were a few ways to address it:

The simplest way is just to have one type of train running at that station. They're moving through their fleet, they could standardize their doors. It's a long term planning issue. But as for the old trains, just run them at stations that don't have the doors yet. They're not going to implement it all at once. They definitely should do it on the most crowded, congested stations.

Cohn believes that installing the doors would address more issues than just people falling on the track:. "Obviously it would stop people from falling, but when we looked at it, it wasn't so much about that—it was also about being able to control the environment on the platform." That means the MTA could better control heating in the winter and cooling in the summer on the platforms; it would also make it easier to evacuate trains, and have controlled smoke evacuations of stations.

Trains are also air-conditioned, so they're pumping heat onto platforms where people are waiting. "The system wasn't designed for that," he noted, saying with the doors, the platforms could be isolated from that. Another aspect that hasn't been discussed: the sliding doors, in conjunction with a system of pumps, could work to protect rail and tunnels from being flooded in low-lying stations.

As for the issue of funding, Cohn believes it would take political pressure from outside the MTA to really make this happen. If the MTA is only concerned about guarding people from falling, then this may not be the right plan: "It's a bigger opportunity to really have an environmentally controlled platform. If they're just concerned with fall protection, there probably are simpler systems that they could do that aren't full environmental enclosures."