11-22-2017, 06:47 PM
(11-22-2017, 03:25 PM)Canard Wrote: @ijmorlan: No city has attempted a Light Rail/Tramway system in an urban environment with crossings and so on automatically. Alstom has done some automated yard-movement stuff in Paris on an experimental basis, but that’s it.
There’s no need - headways can be as close as busses, almost, without automation. There is only a gain in big trains with large stopping distances. I think you are incorrectly extrapolating what is happening in Toronto on the subway to our LRT.
I’m not extrapolating from Toronto. I’m extrapolating from the self-driving car news we see everywhere. If self-driving cars are really possible, then self-driving LRVs, including in mixed traffic, are definitely possible. While it wouldn’t be the best design, simply hooking up the self-driving car’s collision-avoidance system to the emergency brake and making it otherwise exactly like existing ATO systems would work as long as there was a way to disengage the emergency brake when the hazard condition no longer exists.
The fact that ATO is still seen as absolutely requiring total right-of-way separation is one of the reasons why I am skeptical about self-driving cars. But on the other hand, we see things like Uber placing an order for thousands of cars intended to be modified to be self-driving. News like that feels like more than a publicity stunt. So overall, I don’t feel confident in my ability to predict where the self-driving car story is going. But it is definitely much easier to make a self-driving LRT than a self-driving car.
And it does matter because labour is a significant cost. The only reason somebody would even suggest running 2-car trains every 30 minutes instead of single cars every 15 minutes is to save on labour. When the numbers get down to shorter headways then other issues such as line management and how often the crossings trigger come into play but at wider headways the only benefit of longer trains is reduced labour costs.