Doppelmayr told members of the Transportation Committee that its investigation is also covering the question of why the diesel backup system failed to work. In the hearing, Mark Bee played back his understanding of what transpired between the failure of the main drive system and the decision to mount rescue cages.

Bee: From looking at the log, the shift supervisor first attempted to engage the backup diesel system approximately 12 minutes after the original stop. He was ultimately not able to get it operating. The manager came on site; he was also not proable to get that system to operate. They tried to go back to the electrical system and they [still] couldn’t get that system to operate. By that time the decision was to put the rescue Tramway into service. So the backup diesel that’s intended to pull the cars in – we never got that working that night. After everyone was off the cars, the next morning, about an hour and a half later, we got the backup diesel system to bring the cars in.

Liu: I guess it’s a little unclear. What was stated in the prepared testimony [given by Herb Berman] was that the backup drive system couldn’t actually drive the Tram cars because the emergency brakes could not be released.

Bee: Within 30 minutes of the stop we had the backup system running, but were unable to get the brakes to lift.

Liu: But what was it? What was wrong? Was it the auxiliary drive was not working? Was it that the auxiliary drive was working but the brakes wouldn’t release?

Bee: The diesel engine itself did start... The drive system itself was fully operational. But there was a problem within the controls for that system that failed to close the relay that was necessary to open the brakes before the Tram cars could actually move.

Liu: The Tram cars did move for a little bit... Bee: What the operator had done at that time was – there’s a way to manually open the brakes. And when he manually opened the brakes, just because of gravity and where the cabins were, the cabins moved about 30 meters on the line. But he wasn’t able to manually hold the brakes open and at the same time run the diesel standby unit. Because of the safety systems built into the system, it wouldn’t allow you to manually open the brake while at the same time engaging the standby. So it’s correct that the cars did move a little bit, but they moved only because we were able to manually lift the brakes without the diesel system connected, and the cars coasted to the, basically to the low part of the line. Liu: So gravity moved them...

Bee: Gravity moved them, yes.

Liu: ...the Tram cars. And then after the – what – couldn’t you just get another person to hold the emergency brakes open while the first engineer operated the drive system?

Bee: Well, that would be relatively safe while the cabins are between the spans, where it’s not steep. [But] once they cross towers 1 and 3, it becomes very steep, and you would not want to rely on a manually held-open brake and an operator who’s down in the basement in the machine room, who cannot really see the cabins. I think Armando, who was onsite at the time, made an excellent decision to stop trying to bypass safeties and go to a safer mode to get the people off, which was to allow the Fire and the Police and the rescue Tramway to operate to pull people off. There’s all kinds of things that could’ve been tried, some may have been safe, some may Main Drive from page 1 not have been safe, but we’re stuck with the existing protocol, which says that, if we don’t have the system working properly, we don’t start putting jumpers on...

Liu: What kind of routine inspections are made of that backup system? What kinds of tests are run on that system to make sure that it is operational?

Bee: We test the system on a monthly basis. It was last tested on March 31st, and we test and log it every month. On March 31st, the system worked perfectly.

Liu: And so that’s the big mystery right now – that in the 18 days, we’re not sure what happened, where on the 31st of March the backup drive system was operational, and then on the 18th, it wasn’t working properly.

Bee: That’s correct, and that’s what we’re planning to investigate.

Bee was not actually present during the April 18 Tramway crisis. His descriptions of operators’ efforts to get the backup system operating were second-hand. The City Council Transportation Committee did not ask for – and RIOC apparently didn’t offer – testimony from either Armando Cordova, Doppelmayr’s man in charge here, nor from Red Blomer, the Doppelmayr representative who has overall responsibility for the Roosevelt Island Tramway and visits the Island from time to time. (Blomer, for example, was involved in the short-cutting of the Tramway cable several years ago, during a cable-replacement exercise.)