Push/Pull Operation, is it safe ?

[cascaderailroad]

How does Push/Pull operation work ? I am supposing that the pushing locomotive is unmanned on the rear of the train, and is remotely controlled by the engineer riding up in the cab of the unpowered, last car of the train (which is now the head end)

If you have ever pushed a 10 car HO train down the tracks over turnouts, and around curves, surly you have gotten some pretty nasty derailments, as by the time your hand stops pushing, you have already shoved 10 HO cars off the tracks, when it got hung up in a turnout.

Taking for granted that the railcars are extremely heavier than HO traincars ... but still, I would think that pushing a long train is very potentially dangerous, over that of pulling a train

I would think that the reason behind this is that RR's have taken the capabilities wye's and runaround tracks out, and find it cheaper and less time consuming to not have to turn, or run locos to the head end of a train

I am surprised that there have not been many more shoving derailments in push/pull operation

 

[Azervich]

You also have to consider that with HO scale you have a worm drive gearbox so if one motor is powering more than the other the one with less power creates a braking effect which causes the light weight cars to derail, in real life they don't have worm drives so a less powerful loco will just free roll like a car in neutral.

 

[simulatortrain]

In my experience it's almost always model-specific things that cause HO derailments like that. Couplers that center themselves are constantly fighting the pushing force to do so (one reason I choose not to use them) and tight track and rough switches combined with light cars will do the rest. I have some unrebuilt Bachmann heavyweights that will derail if you look at them, which I push through new trackwork to test it. If the track's good they will still make it.

 

[whitepass]

An HO car should weigh like 900lb. I use to run HO then tried N for a short time then G, N derail more that HO and G almost never.

 

[JCitron]

The derailments are also caused by moving the cars too fast through the curves and over the switch points.

Your hand isn't necessarily a scale-speed locomotive.

 

[martinvk]

Plus, despite the name, scale models are not truly scale in all aspects. Mass is one thing that doesn't scale well. Just look at how a model wiggles as it moves on the track. Real wheels are conic sections which help keep them on track too.

 

[teddytoot]

Here in Dorset, England we had push-pull trains between Bournemouth and Weymouth from the end of steam until the line was electrified. A 12 car unit consisting of 2 4-car trailer units with a 4 car electric unit at the rear, ran from Waterloo to Bournemouth. Here the electric unit was uncoupled and a diesel loco attached to the front to haul the 8 car trailer unit to Weymouth. On the return it pushed the coaches to Bournemouth where they coupled to the electric unit and the diesel came off. As the OP suggests the driver rode in a cab at the front of the train. No problems were experienced and in fact high speed tests were done before this mode of operation was approved, as previous to this a push-pull unit could only have two coaches. The difference between this and a model is simply weight; real trains are heavy enough to stay on the track. Unfortunately we cannot vary the laws of physics to suit our models.

 

[bnsfc]

Getting back to the question, yes and no. Would it probably be safer to always have the loco leading? Yes. But there are other practical reasons railroads do this other than they took out wyes and runaround's. In Chicago at least, the cars are custom built to be

push pull and are very heavy, most likely reaching the weight limit depending on how many passengers are "fluffy". they also have very low play couplers to keep the slinky effect down. But this also means that all trains face outbound in Chicago (at any of the

3 stations) so the exhaust is always as far away from the main building as it can get. and the HEP never needs to be disconnected during normal operations. Also the "sets" if you will, can stay together in the yard, so before a run all you have to do is an

inspection and your ready to go. this also has the effect that mid run flips, IE, a train doesn't go all the way to a terminus but stops and heads back somewhere in the middle, is MUCH easier to do.

 

[JCitron]

Getting back to the question, yes and no. Would it probably be safer to always have the loco leading? Yes. But there are other practical reasons railroads do this other than they took out wyes and runaround's. In Chicago at least, the cars are custom built to be

push pull and are very heavy, most likely reaching the weight limit depending on how many passengers are "fluffy". they also have very low play couplers to keep the slinky effect down. But this also means that all trains face outbound in Chicago (at any of the

3 stations) so the exhaust is always as far away from the main building as it can get. and the HEP never needs to be disconnected during normal operations. Also the "sets" if you will, can stay together in the yard, so before a run all you have to do is an

inspection and your ready to go. this also has the effect that mid run flips, IE, a train doesn't go all the way to a terminus but stops and heads back somewhere in the middle, is MUCH easier to do.

This is the same operation used in and out of Boston. We have 6-car trainsets with an F40PH usually on one end and a cabcar at the very end. They used to be all Horizon train cars but there have been a few Rotem Bi-level cars introduced over the years, but mostly on the south-side where the traffic warrants it.

When did this start? I would say in the early 1980s when the Budd Liners (RDCs) finally died and were turned into coaches that were pushed/pulled by former GM&O F units affectionately known as Easter Eggs because of their paint scheme.

and

 

[norfolksouthern37]

If you have ever pushed a 10 car HO train down the tracks over turnouts, and around curves, surly you have gotten some pretty nasty derailments, as by the time your hand stops pushing, you have already shoved 10 HO cars off the tracks, when it got hung up in a turnout.

Most of the time this is caused from the couplers being mounted on the trucks rather than the body of the cars. This is in no way related to how real trains work.

Taking for granted that the railcars are extremely heavier than HO traincars ... but still, I would think that pushing a long train is very potentially dangerous, over that of pulling a train

I am surprised that there have not been many more shoving derailments in push/pull operation

They don't really operate "long trains" this way.

 

[jkinzel]

Talgo

This Talgo train is push-pull and has a speed limit of 79mph. In this photo it being pushed along the shores of Puget Sound.

Regards,

 

[pfx]

Push pull operations have been taking place at 125mph on the UK's East coast mainline for years with a class 91 electric loco at one end and driving van trailer at the other. Before that there were numerous push pull services which were diesel powered across the UK which used modified brake carriages as the driving trailer. Push pull was also commonplace in Ireland and is still used on the Enterprise train service.

As for safety, of all the accidents involving push pull sets, the only one I can think of where there was some blame placed on push pull operation was in Scotland where a DBSO derailed after hitting a cow. There were issues with the weight of the DBSO and it not having a cow catcher (this led to modification of the whole fleet) which ultimately led to the front bogie (truck?) derailing and the death of 12 passengers and the driver.

 

[Vern]

That would be Polmont... https://en.wikipedia.org/wiki/Polmont_rail_accident

And Heck, https://en.wikipedia.org/wiki/Great_Heck_rail_crash with the ECML express in push mode with the Class 91 loco on the rear and DVT on the front. However the root cause was a moron driving when he shouldn't (fatigue), going off the road which supposedly had sub standard crash barriers into the path of the train which then derailed into the path of an oncoming freight. The car driver subsequently served a prison term for his culpability in the incident...and Class 91 push pull operation still continues on the East Coast main line (and West Coast line for a while).

And one in the States - https://en.wikipedia.org/wiki/2005_Glendale_train_crash - also a result of a deliberate act for which the culprit is now serving a long (whole life tariff) prison sentence.

However you have to set these exceptional incidents against the thousands of push pull train operations around the world daily which take place in complete safety and that all of the above came about due to external factors.

The policy in the UK now seems to be towards fixed formation "MU" trains with more even weight distribution - Voyagers, Pendolinos and the superb new Hitachi IEP/Class 800/1 trainsets. Also to put things in perspective a train with a loco/power car at the front can still derail against an obstacle https://en.wikipedia.org/wiki/Ufton_Nervet_rail_crash which was one of the more serious UK rail crashes of recent years but again the result of a deliberate act. Sadly on this occasion not only did the culprit pay with their lives but also the train driver and several passengers.

 

[Mick_Berg]

There was a horrible accident in LA where I live when some idiot left his truck on a grade crossing. The train was being pushed, and I always thought that if the heavy loco had been at the front of the train it would have pushed the pickup out of the way. Instead it just pushed the whole train into the wreckage.
When I was a kid I rode push-pulls in London but these were just two coaches and a steam loco, chugging along at 25 MPH with no grade crossings, very different.
Mick

 

[santafe8643]

Push/Pull operations are quite controversial. One pro is that you don't have to uncouple from your train just to put the locomotive on the other end. However, one con is in the case of the Oxnard crash: the lighter locomotive derailed.

So so it basically depends on the speed and if an objects (for ex: car, tree, box).