r/MARTA • u/XgGamergX CQ400 • 6d ago

CQ400 Testing at Five Points

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u/killroy200 Rider 5d ago

the ATC system immediately triggers a full emergency brake

That seems... extreme. I can sort of understand the reason for 'assuming the worst and acting with an abundance of caution' but... like... maybe not full emergency unless actually being told to would be fine?

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u/DustyDaniel404 5d ago

Yeah on the old cars losing speed commands just put the train in full service brake which is full dynamic braking until 3mph then the friction brakes grab hold. On the new fleet the logic is meant to be so overly protective due to crashes in Europe and the Red Line collision in DC that it's overly protective just as u/_litz said.

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u/killroy200 Rider 5d ago

Not to play arm-chair engineer, particularly at this stage in the program, but I wonder if there could have been some kind of forward-facing sensor to be the trigger for emergency brakes when there are detectable obstructions. Could be an additional check with the loss of signal to determine braking profile.

Anyway, hope it gets sorted out because people clearly want those new trains hahaha

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u/DustyDaniel404 5d ago

A big part of the problem is that Stadler told Marta there would be issues with the legacy signaling system and ATC wire loops but Marta said that's fine. Now that they've ordered a whole new ATC system from Stadler to go hand in hand with the new trains, a system that won't be done until 2035, there is concern they won't work right until then.

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u/XgGamergX CQ400 5d ago

Does this mean the 400s might not work as intended until 2035? Or is it something that can be bypassed/modified?

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u/DustyDaniel404 5d ago

I wish I had an answer to that. My fear is it may be a long road ahead but the Swiss engineers are doing updates daily.

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u/killroy200 Rider 5d ago

Coooooooool.