Paul, I love you, but you are very, very wrong here.
This is CN's fault. It is a CN-specific problem, and so would I argue that it should be up to CN to at least in part figure a solution.
CN's signal design uses a very low shunt voltage - considerably lower than any other railway in North America, to the best of my knowledge - and so there is constantly a battle to try and prevent shorter consists from losing shunt.
A bit of background - I'll be getting into the weeds here, so I apologize in advance.
Shunt is the process by which a train is able to get detected by the signal system and thus trigger things like level crossings, signal occupancy, etc. This is done by ensuring that there is electrical continuity across both rails, first by insulating them from each other and then by ensuring that the wheel and axle unit are electrically continuous. There are other ways of doing this - axle counters are the new trend, and found on a lot of subway systems - but shunting has been around for over 100 year and generally works.
There are a couple of problems at play here:
- The new Siemens trains do not have any brake shoes on their wheel treads. This means that there is no active cleaning of the wheel tread.
- 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).
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.
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. I'm not sure that replacing small portions of CN's signalling network is feasible either, as that may require other interventions where the portions of the signalling system with meet and connect. I'm sure that there are some ways of dealing with it, as CN has signallized level crossings with other railroads, but I don't know how feasible they are for this kind of interchange or hand off.
As I wrote above, Amtrak has been running additional cars of many varying types tacked on to their trains that are running out of Chicago, but only the ones that run on CN lines. CN has also decreed that this rule can be bypassed through the use of a "shunt enhancer" - a device or which Amtrak has been investigating for about a year now, and does not yet have FRA approval for its use.
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. (Want to be really nasty about it? Make CN pay for their development, design, production and installation.) Testing will be required of course, but should this be the solution than a fix should be able to be made within a matter of months. But I feel that the FRA and TC should also weigh in here, and look into CN's own systems and see if they aren't more problematic than other railroads because of this low shunt voltage.
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.
Dan
urbantoronto.ca
