Tram switching directions

[fergusjbend]

This is probably a dumb question - if so, my apologies in advance!

Do modern tramway systems operate in the same way as heavy rail, with signals and remote-controlled points, or do drivers control the points from the cab? Or what......?

Thanks.

 

[edwin_m]

Either or both of these can happen.

On the approach to a junction there is a wire loop between the rails which reads information from a transponder underneath the tram. Usually this includes the route it is taking, so if other conflicting tram routes and road traffic signals permit, the system will immediately set the correct route and also call all traffic signals to stop other movements and give the tram priority. Tram signals work in the same way as traffic signals, but to avoid confusion they use a horizontal white bar for stop and a vertical white bar for proceed. However like the rest of the tramway and like a road, the driver is responsible for stopping short of any obstruction such as another tram or a road vehicle. This is unlike railways where a driver seeing a main proceed aspect is sure of a clear route at least as far as the next main signal.

There is also a second loop just on the approach to the signal, so if the tram does not get priority it will come to a stop on this loop and the route can be requested again. The driver can also do manual requests from the cab, which is useful for trams not running a standard route or for busy stops where it may not be sensible to call the route until the tram is ready to go. In some cases the point can only be called from the cab, particularly in busy pedestrian areas where the driver must make sure there is nobody standing on the point blade before it is moved.

 

[fergusjbend]

A very helpful reply. Many thanks.

 

[tramdan]

Tramways do vary in terms of driver involvement in route setting.

For example on Sheffield's Supertram network, route setting is done automatically via the transponder and loops in the four-foot.

However in Nottingham we have a set of points buttons (Points Left and Points Right) and the driver has to select the desired direction as the tram passes over a points loop. They must select regardless of whether or not the points need to swing as this locks the points in place for the tram to pass over.

There are various kinds of loops that are used across tram systems and the naming varies from system to system, let me know if you want more info on these.

 

[Crossover]

Some parts of Metrolink still runs on fixed blocks (though I think this is now pretty much only applicable to the ex BR sections) with most of the rest now using Line of Sight and points indicators. I believe on the street running sections of Metrolink, the points will only swing with a tram pretty much on top of them, such to ensure no-one is stuck in them

 

[Hornet]

The OP might find this useful, or a bit too Technical, depending. It's a Dublin LUAS presentation.

http://www.tcd.ie/civileng/Staff/Brian.Caulfield/4A8/Luas Presentation.pdf

I worked on several of the LUAS Projects as part of the Design Team.

 

[talltim]

Further to the Sheffield info, some of the crossovers not used for the regular services are manually operated, the driver gets down with a long point lever bar. Trailing points are not changed, just run through the, unless the next team will be facing them.
In the old days, some tram networks had a system wher e the driver could control facing points at they came to them by reversing the power to the team momentarily. Presumably this caused some sort of power fluctuation in the overhead or conduit that activated the point motor

 

[edwin_m]

Further to the Sheffield info, some of the crossovers not used for the regular services are manually operated, the driver gets down with a long point lever bar. Trailing points are not changed, just run through the, unless the next team will be facing them.

Most tramways have three types of point. Those that can be used facing in either setting are motorised, those that can be used facing in only one setting (eg exit from single line) are sprung in one direction, and those that are only used in the trailing direction can just lie where they were last pushed to by a passing tram. However some of the trailing ones can be set to work in sprung mode.

 

[Welshman]

There is also a second loop just on the approach to the signal, so if the tram does not get priority it will come to a stop on this loop and the route can be requested again. The driver can also do manual requests from the cab, which is useful for trams not running a standard route or for busy stops where it may not be sensible to call the route until the tram is ready to go. In some cases the point can only be called from the cab, particularly in busy pedestrian areas where the driver must make sure there is nobody standing on the point blade before it is moved.

My thanks, too, for that full explanation.

I've sometimes noticed a driver pumping a button on the console, and I suppose that was the calling of the route as you describe.
--- old post above --- --- new post below ---

In the old days, some tram networks had a system wher e the driver could control facing points at they came to them by reversing the power to the team momentarily. Presumably this caused some sort of power fluctuation in the overhead or conduit that activated the point motor

Just out of interest, I seem to remember the drivers of the old trolleybuses in Huddersfield could similarly change the points in the overhead by jabbing the accelerator pedal on approach to the junction, thus saving the conductor having to alight and pull a wire on the nearby post.

 

[talltim]

Apologies for my auto-correct not seeming to like the word tram.

 

[edwin_m]

I think the traditional point-changing circuit was an isolated section of wire fed through a relay or similar, so it would switch one way if the tram/trolleybus was drawing power and the other way if it wasn't. There probably would have been some sort of vehicle detector as well.

 

[Crossover]

The OP might find this useful, or a bit too Technical, depending. It's a Dublin LUAS presentation.

http://www.tcd.ie/civileng/Staff/Brian.Caulfield/4A8/Luas Presentation.pdf

I worked on several of the LUAS Projects as part of the Design Team.

Thanks for posting that - I found that interesting from the quick glance through I had

 

[Jeni]

Further to the Sheffield info, some of the crossovers not used for the regular services are manually operated, the driver gets down with a long point lever bar.

I've occasionally seen this done on Metrolink at Piccadilly Gardens late at night. Presumably some sort of malfunction?

 

[WillPS]

Further to the Sheffield info, some of the crossovers not used for the regular services are manually operated, the driver gets down with a long point lever bar. Trailing points are not changed, just run through the, unless the next team will be facing them.

The bar frequently makes appearances doing fairly routine things like the crossover at Cathedral that every Purple Line service uses, amongst others. I guess the automation isn't too reliable... mind you, I've never seen them resort to using them at 'the triangle'.

 

[Stonesourscotty]

Some tramways use both systems I'm pretty sure the Melbourne Yarra Tram network uses both in St Kilda

 

[madannie77]

The old method of automatic points changing was this device or something similar:

http://www.cotma.net.au/library/signals/Collins Automatic Point Turner Sheet 19.pdf

And the manual method as used in Sheffield

https://madannie.smugmug.com/Category/South-Yorkshire-Supertam/i-fJfpNjD/A

 

[tramdan]

The bar frequently makes appearances doing fairly routine things like the crossover at Cathedral that every Purple Line service uses, amongst others. I guess the automation isn't too reliable... mind you, I've never seen them resort to using them at 'the triangle'.

Embedded points tend to be a bit less reliable than those on ballasted track for getting points detection as they are more liable to fill up with debris that washes in from the surrounding street surface. In Nottingham for example, points FOP1 and FOP6 get cleaned out very regularly for this reason.

 

[edwin_m]

Embedded points tend to be a bit less reliable than those on ballasted track for getting points detection as they are more liable to fill up with debris that washes in from the surrounding street surface. In Nottingham for example, points FOP1 and FOP6 get cleaned out very regularly for this reason.

With a Henry on the back of a pickup truck IIRC!