boblothrope wrote:ExCon90 wrote:Signals timed to control speed are common all over the New York City Subway and PATH, and as TrainManTy commented it is perfectly possible to arrange them so that a train proceeding under control at the prescribed speed will see the signal clear up as it approaches, so that no stop is necessary. Apart from the other considerations mentioned, standing passengers, of whom there are many on the Green Line at all hours, find incessant stops and starts to be very irritating.
These always-stop signals are a big peeve of mine.
If the T cared at all about getting people to their destination with speed and comfort, they'd get rid of them right away. They're a major reason why the Central Subway often has stop-and-go traffic from end to end, even outside rush hour.
People driving on the Mass Pike don't have to deal with the delays and discomfort caused by stop signs. So why should transit riders?
It's a generally accepted road engineering principle that stop signs should not be used for speed control. In fact, the MUTCD expressly prohibits it. And most normal passenger rail systems are designed to keep the trains moving, especially in areas that are a capacity bottleneck (and if the Central Subway isn't one of those, I don't know what is).
I'm also not convinced that all-stop signals increase safety. They encourage drivers to speed between signals. And if drivers are blowing through red lights at grade and station timers, that's a bigger problem which won't be fixed by a stop signal band-aid.
There's also the issue of wasted electricity. Can you imagine how much the meter spins every time a Green Line train accelerates up to speed? Multiply that by the number of daily trips on the Green Line, *and* by the number of all-stop signals in the tunnel, and that's a whole lot of money and energy blowing up the stack.
boblothrope wrote:ExCon90 wrote:Signals timed to control speed are common all over the New York City Subway and PATH, and as TrainManTy commented it is perfectly possible to arrange them so that a train proceeding under control at the prescribed speed will see the signal clear up as it approaches, so that no stop is necessary. Apart from the other considerations mentioned, standing passengers, of whom there are many on the Green Line at all hours, find incessant stops and starts to be very irritating.
These always-stop signals are a big peeve of mine.
If the T cared at all about getting people to their destination with speed and comfort, they'd get rid of them right away. They're a major reason why the Central Subway often has stop-and-go traffic from end to end, even outside rush hour.
boblothrope wrote:People driving on the Mass Pike don't have to deal with the delays and discomfort caused by stop signs. So why should transit riders?
boblothrope wrote:I'm also not convinced that all-stop signals increase safety. They encourage drivers to speed between signals. And if drivers are blowing through red lights at grade and station timers, that's a bigger problem which won't be fixed by a stop signal band-aid.
BandM4266 wrote:It's a peeve that a signal stops us for 8 seconds in our day! Why can't the T get us there with speed and comfort.
My question is what about safety? Would you rather a train not stop at one of these safety signals and come around a bend that obstructs an operators view and collide with a stopped train ahead?
boblothrope wrote:BandM4266 wrote:It's a peeve that a signal stops us for 8 seconds in our day! Why can't the T get us there with speed and comfort.
My question is what about safety? Would you rather a train not stop at one of these safety signals and come around a bend that obstructs an operators view and collide with a stopped train ahead?
My point was not about the 8 seconds. It's about the cascading delays which cause stop and go traffic in the entire tunnel, as well as passenger comfort and energy use.
No, I obviously don't want trains running red lights and rear-ending each other. But I don't think pointless stop signals are a good way to prevent that.
I am not 100% sure either, but I believe the types 7/8 use dynamic braking which is different from regenerative braking. With dynamic braking the kinetic energy is turned into electric energy and the electric energy is turned into heat with resistors. The electricity is not returned to the power grid because of the complexity of matching voltages and load. In cold weather, this heat could warm the passengers (I don't know if it does). In the summer, it's waste. The advantage of dynamic braking over friction brakes is that dynamic braking saves wear on the friction brakes.BandM4266 wrote: ... I am not 100% sure about this but aren't the type 7 when in dynamic braking being used as a regenerative motor? Therefore creating power that is returned to the overhead wires to be used to power yet another car? So if so not much energy if any used! ...
boblothrope wrote:BandM4266 wrote:It's a peeve that a signal stops us for 8 seconds in our day! Why can't the T get us there with speed and comfort.
My question is what about safety? Would you rather a train not stop at one of these safety signals and come around a bend that obstructs an operators view and collide with a stopped train ahead?
My point was not about the 8 seconds. It's about the cascading delays which cause stop and go traffic in the entire tunnel, as well as passenger comfort and energy use.
No, I obviously don't want trains running red lights and rear-ending each other. But I don't think pointless stop signals are a good way to prevent that.
GP40MC 1116 wrote:It's been explained here more than once why the T has stop signals in strategic locations for safety related reasons. Therefore those signals are not "pointless"
GP40MC 1116 wrote:If you don't like the 8 seconds delay, go hop in your car and see how much faster it gets you to your destination.
boblothrope wrote:GP40MC 1116 wrote:It's been explained here more than once why the T has stop signals in strategic locations for safety related reasons. Therefore those signals are not "pointless"
Do you have crash statistics from before and after the stop signals went in?
I don't, but the general sense I have is that a rear-end accident happens every few years on the Green Line, and this hasn't changed as more and more stop signals are added.
boblothrope wrote:If the safe speed for a stretch of track is 10 mph, make sure the drivers go 10. Not 0 and then 10.
boblothrope wrote:And please stop with the 8 seconds. I explained how the inefficient throughput of the signal system causes stop-and-go traffic for the length of the tunnel much of the time.
boblothrope wrote:Do you have crash statistics from before and after the stop signals went in? I don't, but the general sense I have is that a rear-end accident happens every few years...and this hasn't changed...
boblothrope wrote:Telling people, "Yeah, riding our transit system is an awful experience, but hey, it's better than driving!" is not the way to improve quality of life in our city.
boblothrope wrote:And please stop with the 8 seconds. I explained how the inefficient throughput of the signal system causes stop-and-go traffic for the length of the tunnel much of the time.
CRail wrote:The theory is if your brakes have failed, you have more time to figure out what to do than if you realize your brakes failed 50 feet away from the car ahead of you, or even closer to a sharp curve. It's not for speed control, it's to ensure the operator still has control.
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