New trains: padded schedule
Old trains: padded schedule
So really, all train schedules are padded - which makes sense, you need buffers to absorb variance in performance to have reliable schedules.
back
1 comments
> Old trains: padded schedule
No — Old trains: schedule based on experiences from having ran them for at least a year (i.e. all seasons)
New trains' buffers are larger because you don't know e.g. how shit the brakes are when you have tons of leaves on your rails. (Yes this is an actual thing¹.)
[¹ Ed.: in case anyone is incredulous at the leaves thing: https://www.groupe-sncf.com/en/group/behind-the-scenes/traff... ]
The contact surface area of a steel wheel on a rail is about the size of a dime. That's what you have to work with to stop the train.
To drive the train. But to stop the train, surely the contact surface of the brakes with the wheels is more important?
Just like on a car, if your break pads are capable of completely stopping the wheel, but the wheel is not capable of creating enough braking force with the surface, then you slide. If you lubricate between the wheels and surface, which is essentially what leaves do on rails, no amount of at-wheel breaking power will stop you.
This is what antilock Brakes in cars prevent, they pulse the brakes to allow the tire to regain traction, preventing slippage and loss of control.
Note that a modern train also has the same system, only more so, a car would typically have 4 wheels, I think the Acela probably has like 96 or something.
There's also some "infant mortality" stuff, the EMUs (Electric Multiple Units, which I suppose is roughly what this is?) in my country have not good failure rates in their first weeks and months but they get much better (typically best in class due to fewer moving parts than say a diesel) in mid-life.
Brake performance is a thing you can simulate and measure on a test track, which presumably happened at least months ago. However loss of adhesion, the reason braking stops working on contaminated railheads is also impacted by moisture, a bunch of dry leaves won't make anywhere close to the same problem as the same leaf material after a nice gentle drizzle, not really rain per se, not enough to actually wash the rails clean, but ensuring the leaves turn into a thin mush that makes braking next to impossible.
RAIB report 12/2023 about an incident near me talks about that, the driver maybe makes some dubious decisions, but ultimately he brakes, and it does nothing, so he brakes harder, still nothing, maximum braking, still nothing, select emergency braking (same effect but hey, it's there to be used right), still nothing - oh shit, we've passed the danger signal and I see another train, time to leave. He actually spent ages in hospital because he tripped trying to flee and was trapped in the wreckage, but on the other hand if he'd just sat there frozen he might well be dead 'cos his train did indeed smash into the other one so the side where the driver is sat smashed into another train at like 50+mph.