Which should make it easier to pile on lots of other information, like onboard defect detection…
So the train gets to its hold-out parking spot a little sooner…
One feature that, to my knowledge, has not been included in Electric\electronic braking systems tested so far, but must be included is:
A rapid sharp drop in train-line air presure, that would execute an emergency stop by propgation of the pressure drop alone, must also activate the electrical\electronic emergency braking.
This wiould have mitigated both the Megantic and the East Palestine damages. Brakes should apply unbiformly under all conhditiond, including vedmergencies.
It does already, on both systems. The immediate actuation of all emergency valves in the train simultaneously, rather than ‘at the speed of sound in compressed air’, is what produces the roughly 3% reduction in achieved stopping distance.
I do not know whether providing an ECP emergency trip at each emergency valve, to be triggered when any valve in the train physically goes to emergency, or if the trainline pressure drops ‘uncommanded’ below a critical level, is part of current systems. A problem with it is that any sort of UDE instantly slams the train into full emergency without warning, but all the issues with brakes applying differently or slack condition still apply regardless of how quickly the valve modulates.
This is correct Dan greater wear was reported in the initial testing of ECP. However that was only because of being unfamiliar with the advanced braking system. As Engineers gained more experience using ECP. Wear reduced considerably over conventional ABV equipment.
The stopping distance is a bonus of ECP yet imagine with improved braking how many grade crossing incidents could potentially be avoided? Or even low/medium speed rail collisions? ECP has shown to reduce fuel usage, and improve wheel condition by allowing precise modulation of braking. This has led to lower wheel temps especially on descending grades where temperatures have been recorded at lower temps than trains using conventional ABV/DB.
The attributes Don list that are known about ECP are not immaterial and would provide saving to the industry, but we know the C1’s don’t like high upfront cost that will actually save them OPEX in the long term… Yet 75% of the fleet being private is the issue in this case. Not the C1’s.
We can’t forget good old inertia. No matter how quickly the shoes are applied to the wheels, a railcar is going to follow Newton’s laws and keep right on going until the combined friction between the shoes, the wheels, and the rails is sufficient to have an effect on the car.
I believe it’s been reported that fifty cars derailed at East Palestine. If ECP had cut that number in half, there still would have been a spill and a fire.
And, I go back to the well-known video of the train struck by a tornado. It’s very clear that the brake line had parted, which would initiate an emergency application throughout the train, yet the remainder of the train still piled into the trailing locomotive at a pretty good speed.
Dan posted: " If PTC turns out to be the thing that enabled a reduction in crew size, then it might - MIGHT - earn back it’s cost some day."
Well, since most road crews are just two guys now (engineer and conductor), you’re saying that going to “engineer-only” crews will be the solution that permits PTC to “earn back its cost” ???
Not just one person, they’re already chomping at the bit for no man crews. PTC and the EMS auto throttle move that goal so much closer. So they think.
Jeff
You’re going to fail your Physics class! 
Brake shoe force develops pretty quickly. If that force is equal to 20% of the car’s weight, than you’re going to decelerate at 1/5g or 4 mph/sec. The weight of the car is irrelevant.
The reason trains “take a mile to stop” isn’t inertia or train weight, it’s that brake systems are set for empty cars. An empty that can do 4 mph/sec deceleration can only do 1 mph/sec loaded. If the brakes were set for loaded cars, that train could reduce stopping distance from 1 mile to 1/4 mile.
I think they are chasing the wrong goal! (again) A slow train with a “no man crew” is still a slow train. It consumes a huge number of locomotive and car hours to go “not very far”.
How about trying to lengthen the crew districts by squeezing out all the time not moving or moving at resticted speed? Two men going 300 miles should be cheaper and more valuable than “no men” going 120 miles.
FWIW Amtrak’s Autotrain does 800 miles on two crews over frt RR territory with max speed of 70 mph and “freight braking” system (no graduated release) and about 2 HP/ton.
Track conditions permitting, you could double restricted speed since ECP braking at lower speeds cuts stopping distance by more than half. (the higher the speed, the lower the advantage)
So, maybe that yard congestion goes away, too?
If you are only going to look at ECP for it’s effect on braking on each individual train, you are 100% correct.
You’re probably a lot less likely to pop cars off on curves due to long car/short car/empty/loaded disparities with ECP emergency application. But, that alone won’t get you your ROI.
Braking distance scales with the square of the speed, so halving the breaking distance would give about a 41% increase in speed.
You need a more complex formula, because the advantages of ECP braking are not how strongly the brakes can apply, but the speed and effective precision with which they can be applied. In addition, one of the ‘points’ with graduated release is that a relatively heavy fast set can be partially released a la Decelakron as train speed decreases with less risk of wheelslide.
I hear a lot of stories from various sources (including here on the forum) about trains being held out miles from their destinations because there is “no room at the inn.” ECP isn’t going to cure that.
Does ECP make a full emergency application to all cars simultaneously if the train breaks in two? If so, is this activated by the parting of the electric line?
If so, how does this work in detail? If the electric line parts, there is no power from the parting location to the end of the train. So what communicates to the unpowered cars and provides the power for them to send their emergency reservoir air into their brake cylinders?
Maybe? I kind of doubt it. Are cars really designed for the purpose of survive emergency slack run-in? They’re designed to handle normal in-train forces, many of which occur without the automatic brakes being engaged at all, and forces experienced during switching and coupling activities. For the structural elements of the car (as opposed to the draft gear), surviving over speed coupling events (i.e. 6+ MPH collisions) may be limiting factor.
In what context exactly? The reservoirs still have to be charged from the train line.
This would have some benefits, but less than you might think. If every train origination and on-line pickup still requires someone to walk the train inspecting other features of the car (such as safety appliances), then automating the brake test has less value. If you can automate inspection of other features - which the industry has been working on for decades - that would help.
On the mainline, most contexts requiring restricted speed are either a.) solvable by the more-advanced train-control systems that are in the works, thanks to PTC, or b.) protecting a potential track defect such as a broken rail, where there is good reason to limit speeds anyways.
In yards, 80-90% of all tracks are limited to 10 MPH by turnout size and track condition. And many movements within the yard don’t have air cut in except on a few cars on the head end. (If braking performance was limiting yard capacity, we could start by using more of the existing brakes.)
Because why? See #
Interesting questions and I don’t think anybody can really claim to know the answer for sure. But I think the most likely answer is that it would make almost no difference. Unlike service braking distances, the difference in emergency braking distances between ECP and state-of-the-art-practice conventional air brakes is quite small. The time from when a typical GCI or pedestrian / trespasser strike is foreseen to the time it happens is still tiny compared to the time it takes for a train to slow significantly.
Dan
I know I’ve seen info on how long it takes for an emergency application to travel the length of the train, but I can’t find it at the moment.
It’s important to note that unlike a service brake application, where all of the air from the brake line vents at the controlling locomotive, with an emergency application, each car also dumps the brake line as it senses the rapid drop in pressure. Thus the emergency application is telegraphed the length of the train quite quickly.
ECP may apply all the brakes in emergency at the same time, but that time difference will be negligible when the physics of the operation is considered.
Modern EOTs can also make an emergency application, so it’s happening from both ends. I can’t speak to how DPUs work in that regard.
After that, it’s all coefficient of friction. The train will stop when it’s good and ready.