Greetings and operational/technical questions

Hello all! I'm new around here... just found this forum recently while searching for some general railroad info. I've definitely always been a railfan, but I never really paid that much attention to the technical side of things. More recently, I've become more interested in that side, in large part because of a city- and transit-building project I've been working on (i.e. the creation of a fictional city and its surroundings, and the transit systems to go with it). So, to that end, I had a couple of specific questions about train operations (passenger, specifically, not freight) that I haven't been able to find answers to by simply scouring the internet. I'm not planning to map out every single aspect of day-to-day operations down to every last revenue trip for this project or anything, but there are some more general things I've been wondering about. Apologies if this post is a bit long; I'm kind of wordy and always want to make sure I'm making my questions clear!

One is about cab-cars and "push-pull" operations. To put it simply, you could say I've been wondering about the disadvantages of pushing + using cab-cars. The advantages are fairly obvious. But, I read a Wikipedia article a while back on the 2005 Glendale crash involving LA's Metrolink, that vaguely mentioned that "some people" theorized that the severity of the crash might have been made even worse by the fact that the train was in push mode, with a cab-car leading. I assume this is simply because of the fact that with a locomotive at the front end, you have it serving as a kind of "buffer"; it would obviously have a much easier time shrugging off/plowing through obstacles than a cab car, so the latter might derail and take other cars with it, whereas the former would simply take some damage but stay on course. But I wanted to know if there was any more to it than that (the Wiki article didn't get any more specific than "some people said this could have made it worse", and didn't cite sources). And of course, on the other side, if the loco is leading, and the obstacle it strikes is heavy enough to not just be tossed aside (say, another train), you can have telescoping, which is obviously bad (and is exactly what apparently happened in a later Metrolink crash, in 2008, again according to Wikipedia anyway)...

In addition, I saw someone on this forum (unfortunately, I don't recall the thread or poster; I should have bookmarked it) lamenting that the whole push-pull thing had become so widespread among North American commuter railroads (apparently, push-pull operations is something that got started in Europe and caught on over here). So, in addition to clarification on the real ups-and-downs of cab cars/push-pull as far as safety goes, I'd like to know what other disadvantages there are of operating this way.

The second question is about something I assumed for years when I was younger, but later figured out wasn't the case. When I'd see passenger cars linked up, with riders being able to walk between them through those connections, I always just assumed that there was a similar connection between the very first passenger car (or baggage car if that's what's up at the front) and the locomotive. This obviously isn't the case; putting aside instances of two locos at one end (you're not going to walk from one, into the next one through its nose), I noticed that on Amtrak, for example, such a connection wouldn't even be possible in some cases (the door on a Superliner would be far too high to allow foot travel between it and an F59PHI or GE Genesis). As I said, when I was younger, I just assumed that for the crew to be able to freely walk between the loco and the rest of the train was standard... then, for years, I just never gave it any thought one way or the other, until I started noticing photos that really made me realize that no, that totally wouldn't work in many cases. So the question is: has that EVER been standard? Or did that concept come completely from inside my head when I was a kid? I had also been assuming that for the crew to be able to interact directly (i.e. not just over communications equipment) with the engineer(s) was somehow important, but maybe that's only really the case if there is some kind of serious problem (in which case the train will probably come to a stop anyway)?

Thanks in advance for any information!

Disadvantages of push-pull?

I've never operated one, but it would seem to me that the major disadvantage would be a derailment while in the "push" mode would cause the locomotive to keep pushing the derailed car, possibly jackknifing the cars and fouling adjacent tracks. This could happen if the trainline connection was not broken, which is common in minor derailments.

When a car derails, rolling resistance increases dramatically. A locomotive pulling on the train would stretch the train out, helping keep it parallel to the track. A pushing locomotive would have the opposite effect.

Passage between the locomotive and train cars? In the beginning of streamlined trains, the locomotive was part of the lead car. No problem there.

In North American practice, engine crews are changed out at terminals. There is really no need for physical passage between locos and cars when the train is in motion. This was possible in certain configurations, however.

North American cab units (both A's and B's) have crew doors at the ends. Sometimes the enginemen need to be able to pass between units without having to go onto the ground. Passage between units aids in doing daily inspections, starting engines, starting or shutting down steam generators, etc. So if the cars used are single-level with doors on the ends, and the locos are arranged with the rear of an A or B unit next to the lead car, yes, it would be possible to go from the train car into the locomotive.

If you have a hood unit on the train, or an A unit facing the train, there would be a big safety problem. Hood unit walkways are typically higher than passenger car doors, and the walkway is protected by a safety chain. Some locos have a short folding plate that could be lowered for passage, but it would be too high to use to get into a passenger car.

Most all of the older-type can units had nose doors, but with no folding plate, they would be too dangerous to use. One special locomotive model, the E4, had a retractable nose door for this purpose. A units were not intended to be linked nose-to-nose, or even nose-to-tail. In later years, when A units were linked this way, nose-mounted m.u. cable receptacles had to be retrofitted to allow this.

When I was a little kid, I, too imagined this was possible. I could imagine dining car waiters bringing rolls and coffee to the engineer and fireman. Sorry, I don't think so.

Les

Another disadvantage of push pull operation is the limited ability to regulate and/or monitor the engine in push mode. There is only so much you can do from a cab car. Additionally, cab cars tend to weigh less than actual engines, so this can work against you when it comes to snow covered grade crossings.

the locomotive won't keep pushing, in case of emergency once air dumps the PCS(pneumatic cut out switch) will open and traction is lost.
as for strenght a cab car has same buff strenght as a locomotive, it may be a tad lighter but still heavier than anything on other than heavy rail.

A train does not always go into emergency when it derails. If the cars are more or less still in line, a derailed car can bounce along the ties without the train line disconnecting.

In a pushing mode, this could easily lead to jackknifing. When the cars jackknifed, the train line would separate, but by then another track could be fouled.

Les

so now you presume the engineer/ conductor or passengers won't dump during a derailment ? watch to many movies lately ??

At the speeds the scoots run, a minor derailment could become a major jackknife before the engineer could even react.

Run any trains lately?

Les

Desertdweller wrote:A train does not always go into emergency when it derails. If the cars are more or less still in line, a derailed car can bounce along the ties without the train line disconnecting.

In a pushing mode, this could easily lead to jackknifing. When the cars jackknifed, the train line would separate, but by then another track could be fouled.

Les

Sir:

I don't know what a "scoot" is, but this is an accurate portrayal. I'm thinking of 3 low speed incidents in NY that involved NJT trains. They derailed while in push mode. The engineer didn't know it and in two cases, they actually notched up as it was on the ground. In those cases, the train bunched up and jackknifed before going into emergency. In the other case, the train remained up right, but the engine didn't, causing the train to dump.

Desertdweller wrote:At the speeds the scoots run, a minor derailment could become a major jackknife before the engineer could even react.

Run any trains lately?

Les

yup Junior, been operating push pull for last 28 years now, at speeds upto 90 mph. you like to fill me in on your knowledge ??

Thirdrail7,

Yes. That is how it happens.

A "Scoot" is a local name for the push-pull commuter trains used in Chicago. I think the term started on the CB&Q.

Les

Dutch,

Then you ought to know.

You are telling us that you can plug a derailed commuter train in push mode, running at speed, before the compression force from the locomotive causes it to jackknife? That is what I think you are saying here.

And because you can do this, push-pull trains running in push mode are just as safe as if running in pull mode. Or just the ones you are personally running?

Remarkable.

Les

Well, I didn't expect to cause such a stir! Thanks for all of the info so far.

So from what I am gathering, aside from the somewhat disputed issues of safety, there really aren't any other disadvantages of cab car/push-mode operations that are worth mentioning.

As TO the safety issue... if I'm understanding correctly, the idea here is that there are emergency safety measures that would kick into place if a break in connections between the locomotive and the cars occurred (which is what is meant by "breaking the train line"). But in push mode, if it's the loco that derails, the engineer might not realize it until it's too late (and the train line would not be broken until after jackknifing has occurred). This is the potential problem scenario, and what essentially happened in New York in ThirdRail7's examples, yes?

Now, the argument about how true this is/how much of a concern it is... well, some of it is lost on me due to terminology, which I'll ask about now.
-What is "dump"? DutchRailnut refers to it as something the engineers or passengers could "do" during an emergency. ThirdRail7 mentioned one of the NY derailments ultimately caused the train "to dump".
-Plug? Would that be breaking the train line intentionally in order to trip emergency systems? That's what I got from the context in Desertdweller's post ("...you can plug a derailed commuter train in push mode, running at speed, before the compression force..."), but I'm not sure.

Dutch, I'm obviously no expert (hence this thread's existence), and you mentioned that you run trains yourself, but as far as what has been posted so far in this thread, I have to say that the opposing arguments make a bit more sense to me at this point. Especially given the examples ThirdRail7 mentioned. (Not discounting the possibility that I am simply not fully understanding everything here; certainly some of the terminology is unfamiliar to me, as I mentioned above). Also, in regards to the relative strength of a loco vs. a cab car: the weight difference, from what I can find (looked up weight figures for Kawasaki C3, Bombardier bi-levels, DE30/DM30 LIRR locos, and GE Genesis) seems to be 100,000 pounds or more (the cars all weighed in around 150k or less, the two locos weighed in at between 250k and 300k). That really doesn't make a difference when colliding with non-rail vehicles? Further, in the 2005 Glendale Metrolink crash I referenced before, the cab car derailed and jackknifed after hitting the SUV that had been left on the tracks. Is it really just as likely that the same fate would have befallen a locomotive?

I've also observed that LIRR seems to run dual locos, one at each end, with trains made up of DE30/DM30 locos and C3 cars... but only sometimes. I've seen vids of trains with a locomotive at each end, and vids of trains with only one, with a cab car at the other end. Anyone know what that's about? I had wondered about the feasibility of a transit agency or railroad having a "always lead with a loco" policy... obviously this would require either ALWAYS having a loco at both ends for every revenue trip, or a way to turn the loco around at a terminus (does ANYONE still use turntables? They seem to be mostly obsolete as far as I can tell. I wonder if this would be viable though?).

As for walking between the loco and passenger cars, it seems like this might be possible sometimes, with certain locomotives and cars, but certainly can't be counted on, and isn't in any way "standard" or necessary for proper operations. Thanks for the info on that, Desert.

Thanks again to everyone for any and all information. When I started building this project, I was aiming fairly low as far as the complexity of the commuter rail system, but its since grown quite a bit in scope, and I was simply no longer satisfied with my lack of knowledge in this area!

Desertdweller wrote:Dutch,

Then you ought to know.

You are telling us that you can plug a derailed commuter train in push mode, running at speed, before the compression force from the locomotive causes it to jackknife? That is what I think you are saying here.

And because you can do this, push-pull trains running in push mode are just as safe as if running in pull mode. Or just the ones you are personally running?

Remarkable.

Les

There is no compression forces, name any Push pull accidents other than one in California where a engine block hit a switch stand trew it in diverting and train hit a standing train accident where casualties resulted in fact that train whas in push mode....
Each and every unit has same braking power, be it engine or car.
now explain your experience in push pull operations or in general railroad operations, mileage will vary...

Saito:

Plug the air; dump the air; it means the same thing: to initiate an emergency brake application by moving the automatic brake valve handle to the "emergency" position. This is something the engineer would do to stop a train as quickly as possible.
As Dutch alluded to, this would trip the "PC" circuit on the locomotive. When this happens, the throttle drops to idle and the generator field cuts out, as well as emptying the brake reservoirs and the emergency brake reservoirs into the car brake cylinders.
The brakes on the locomotive will set up faster than the brakes on the cars, so if you are plugging the train (while the locomotive is on the head end), you also have to actuate the independent brake to prevent a serious slack run-in.

Dutch:

When a train is being pushed by a locomotive under power, there has to be a compression force acting through the train. The slack is run in against the locomotive. Only if the locomotive were providing no pushing force against the train would there be no compression. The locomotive is overcoming the weight of the cars and inertia (and maybe gravity as well).
If it is only the locomotive that derails, then, no. This would result in a tension force as the slack runs out.
But if it is the car(s) that derail, the loco will keep pushing against them until either the engineer dumps the air, or if the trainline separates. This compression would result in the jackknifing.

Since you asked, no, I have no experience running passenger trains. But the laws of physics are the same.
I have 16 years experience as a freight locomotive engineer, and another ten years in station and operations management. I have had considerable experience controlling shoving movements in switching operations, including working in open-pit mines.
Often these movements involved spotting long cuts of cars down steep grades to a stop against bumpers. Sometimes loads that involve shoving against a set, spotting by chopping the throttle. Compression verses tension, and knowing where your slack is.

I've also had considerable experience running unit grain and coal trains, often with Distributed Power. The last train I ran was a 14,100 ton coal train in New Mexico.

I've served as Supervisor of Locomotive Engineers on several railroads, and personally trained 25 engineers. I've completed the SLE course at Johnson County Community College in Overland Park, Kansas. As you probably know, this school is run by the BNSF as their primary training school.

When I was SLE at Mississippi &Tennesse Railnet in Mississippi, our railroad won the Jake Safety Award.

I retired 85 weeks ago.

Now, tell me about yourself and maybe we can trade some stories.

Les

Saito:

If you have the right equipment, you don't have to lead with a locomotive. Most push-pull trains use a special cab-equipped car as the rear car, so that car can be used as the leader on the way back with the loco at the rear of the train. This car is not powered, but has a driving cab for controlling the locomotive and brakes. It would also have headlights, horn, bell, etc.

I don't know the current practice on the Long Island RR, but I know they used a de-powered locomotive as a cab car on the rear of the train to control the train on the way back, with the locomotive pushing on the back end. The trade-off for doing this is you do not need any special cab-equipped passenger cars. Old locomotives can be stripped of their power systems and be put to use like this.

You do not need any special equipment to pull a train back to its starting point. Just use a locomotive that can be operated with each end leading, or use two single-ended units back to back. At each end of the run, have a double-ended siding or pass track at least as long as the train. Unhook the loco, run around the cars in the siding, and hook onto the other end. Hang a rear-end marker and you are ready to head back.

Turntables are almost extinct. Today locos and cars are turned by using a weye, or less often, a balloon track (reverse loop).
The purpose of turntables was to line locomotives into roundhouses or radial tracks. They were also handy for turning steam locomotives or other single-ended locomotives. The big disadvantage of turntables is, a disabled turntable can trap a whole enginehouse full of locomotives. And, sometimes, locomotives would fall into the turntable pit.

Steam locomotives required a lot more shop time than Diesels. Diesels are often not kept indoors, except to be worked on, and sometimes not even then. A simple shed with parallel tracks reached by switches is good enough for Diesels.

Les