crs1026
Superstar
Paul, I love you, but you are very, very wrong here.
I may be making some different conclusions (but the love is appreciated, and back at ya).
- CN's abnormally low shunt voltage means that it more susceptible to continuity problems with dirty track or dirty wheels. This is why there are all sorts of rules in their rulebook about requiring more than 12 axles in order to allow a train to proceed at track speed (fewer axles are limited in speed in order to ensure that they to shut all of the track circuits).
This is where I think we have to take the longer broader view. CN has run its idiosyncratic signal design for many decades, and never has a regulator or government told them to get with the plan and standardise with other railways away from the low voltage designs. So effectively, what they are doing is legitimised technically and in a regulatory sense. Signal engineers on other railroads may roll their eyes and mutter, but if CN's practice has never been challenged, it "meets code" just as well as what the other railroads do. Hence my view that there has been an elephant in the room all along.
The first issue is a known problem in the sense that the railways have all been here before - although never with a trainset as long as the Ventures + Chargers - and has a known solution. Amtrak out of Chicago has been dealing with CN on this issue for a couple of years now, and their way around it was to tow additional cars in each consist in order to get enough wheels to ensure continuity. Historical, CN resolved this problem with their RDCs - which also don't have any tread brakes - by installing "scrubbers", a small brake shoe that sat on the top of each wheel by gravity with the sole purpose of wiping down each wheel face and making sure it was clean. But even with scrubbers installed, CN still required a minimum of 3 RDCs in order to operate at track speed in any territory that had signalling.
Again, when CN made these demands in the US, nobody told them to smarten up. CN's infrastructure was there first. Amtrak may have caved, er, conceded.... but they added the extra cars instead of seeking support from say the FRA. I don't know the details of CSX's involvement, but one assumes they had some signalling that was of like kind or they had similar experiences.
VIA's bulletin indicates that they are reluctant to start messing with lengthened Venture consists, but it's a pretty obvious and pragmatic solution, and is just an extension of that older RDC and light engine rules doctrine.
We both have enough photos in our collections of 2-car CN and VIA RDC consists in signalled territory to know that CN cut itself some slack in past decades when convenient. That's what has changed.... these days, once the problem is admitted, it cannot be downplayed by management, regulators or by company lawyers, even once in a while. Zero public tolerance.
The second issue is far, far harder to fix - in fact, considering the size of CN"s network it may well be impossible. While increasing the shunt voltage would resolve a lot of continuity issues, it may well require the replacement of hundreds of thousands (or even millions) of additional signalling components.
This is the thing. Directing CN to pull up its socks would likely be a huge legal fail. Possibly as PTC has rolled out and newer flavours are being implemented, CN has positioned itself to gradually solve this problem - but I suspect that to CN shareholders, this ain't broke and doesn't need fixing: Just tell Amtrak/VIA to go away.
So, what to do? In the short term, I can't help but think that sourcing and installing scrubbers on the Ventures + Chargers will help resolve the situation.
I would love to see the graph that shows that 24 axles is not acceptable but 32 is. How is that threshold determined? As a non-engineer, possibly scrubbers plus 28 axles would bean interesting calculation.
(Want to be really nasty about it? Make CN pay for their development, design, production and installation.)
As per above, I can't imagine this would ever happen.
It should be noted that the Chargers and Ventures are running in lots of other places in the US, and on multiple different railways - sometimes in shorter consists. CN's network is the only one where they have these issues. As well, I have not yet heard of one instance on the Kingston Sub where a Charger has failed to activate a signal or level crossing, so this may be a situation of "an abundance of caution" versus a singular or small multiple of actual instances.
I am taking the high road here and accepting CN's concern as bona fide, although one wonders if they are simply playing a trump card as a strategic paper cut against passenger trains on their network. I alluded to CN pushing other agendas - the summer heat speed restrictions on jointed rail is one I would point to, as possibly a vast overstatement of the risk of sun kinks. Whole lot of knowledgeable railroaders scratching their heads about that one, doesn't help that CN exempts itself from those rules in some locations. So maybe this is a bit of malicious compliance, but I think CN may hold the winning cards.
- Paul