The Massive Obvious BUG Thread

[Kromaatikse]

Shunting practices vary very widely. In the US, modern practice appears to be that a full-sized locomotive is signalled into a yard, then given the run of it. In Britain, on low-intensity lines this may also be true, but many shunting yards are explicitly controlled using dwarf signals and have specially-designed shunting engines (like the Class 08). In old practice, the section containing the yard could often contain a section of main line, used as a headshunt to save the costs of providing a real one.

The main trick in shunting is to give the driver information about when it's safe to proceed, and very precisely (to within about a foot) how far. In the US, this is now often done by giving the driver a remote-control unit, so he really can walk along the train and inspect the couplings himself. Nearly everywhere else, it's more normal to keep the driver in the cab, and instead have a person on the ground giving him hand-signals. Where dwarf signals are provided, the handsignals provide a finer grain of information, including how far the couplings are apart.

Another big difference between areas and eras is in the type of coupling. UK practice has long favoured the "three link" coupling (chain and outside buffers), and although this is now being phased out, there is still so much heritage stock with it that all locomotives worthy of the name (and many wagons and carriages) are still compatible with it on some level. This coupling is very simple to make, but is very labour-intensive (and a bit dangerous unless procedures are well followed) to operate. An alternative common on narrow-gauge lines (due to sharp curves and low budgets) is the centre coupling, where a combined drawbar and buffer is provided, and these are linked directly together using a bar and pin.

The accepted modern alternative, near-universal in the US and also quite common in Europe, is the buckeye coupling, where the coupling itself is made semi-automatically, and only brake pipes and electric cables (if present) have to be connected by hand. DMUs and EMUs often have an all-in-one fully automatic coupling (Scharfenberg?) which makes mechanical, electrical and air connections under push-button control, and this allows trains to be split or combined safely under only the driver's control. Before the introduction of this fully-automatic coupler, some areas mounted the cables and pipes high on vehicle ends ("bagpipes") to make things safer for shunting staff, rather than at or under the buffer beam.

Note: to join two passenger trains as is sometimes done at major stations, it is necessary for one of them to enter an occupied signalling section. This is a major function of shunting and calling-on signals in station areas. Nowadays, it is operationally simple since the trains are frequently DMUs or EMUs with fully-automatic couplings, and the passengers only notice that the doors are shut for a moment during the wait and there's a slight bump. In earlier times, you would have to extract a locomotive from between the two trains, which explains why many major British stations had or still have crossovers half-way along the platforms (see York in RW).

The BR manuals said that to make a three-link coupling, the procedure was to come to a stop with buffers about six feet apart - the train would have brakes applied, either automatic brakes or handbrakes as necessary. Then, under handsignaller control, use minimum power to make contact, compress the buffers, then immediately apply the brakes fully and remove the power. Inform the shunter (person) that he may make the coupling (which means lots of screwing and then connecting pipes, while between the locomotive and the train). The shunter would then inform the driver that the coupling was ready, usually with another handsignal, once he was clear. Depending on how far the train was to go in this state, a brake test might be performed (charging and discharging the brake pipe to ensure continuity).

(Yes, I said I'd describe the other half of the brake system. I've been busy, okay?)

[AndiS]

Kromaatikse, AndiS and others posters, thanks for all the information in this thread, although it may be somewhat disconnected from RW and would perhaps suit the generic forum better.

I answered it in the scenario forum, because I fail to make the slightest connection to Massive BUG beyond what I already said.

[osasto]

You'll need to be specific about country and period, as shunting practices vary considerably

Anything goes. I find the information interesting all by itself, but it would also help in coming up with a generic enough design or set of rules so that a simulator could represent various countries and periods with minimum workarounds and oversimplifications.

In Britain, on low-intensity lines this may also be true, but many shunting yards are explicitly controlled using dwarf signals and have specially-designed shunting engines (like the Class 08).

Thanks for that. I suppose dwarf signal is just another name for shunting signal?

I answered it in the scenario forum, because I fail to make the slightest connection to Massive BUG beyond what I already said.

Ok, I'll continue the discussion over there then. I need some time to digest your post but it seems you understood spot on what I'm looking for.

[AndiS]

I suppose dwarf signal is just another name for shunting signal?

Dwarf signals are those on the ground, without a post (or with a post that is a foot long).
The majority of shunting signals are ground signals and almost all dwarf signals are shunting signals.

[jkxx74]

I'm not a freight train fan but reading the above I'd love assembling trains and moving freight around with challenges such as having to squeeze in between other traffic sharing the line. It doesn't look like that'll be possible any time soon though. Otherwise very interesting description of shunting movements from all who contributed information.

-jkxx

[salopiangrowler]

shunting in the UK is undertaken by 08s at major yards and terminals whilst branchline yards are shunted by the train loco (unless there is a weight limit) so its mixed

[boleyd]

The information in this thread is very good. Since I am very far from knowledgeable on rail operations it is perticularly valuable to me. While some points may be debated it seems to offer excellent guidelines as to how both the railroad and the equipment should function. There should be some way to preserve this so it is not lost amongst the noise!!!