Orange light in tube stock cabs?

[Chinny]

Another commute home another question.
I was got on a met train at uxbridge and noticed a orange light in the cab but positioned to show straight back out the window, seems very adhock???

Can anyone tell me what it is used for?
Thanks

[1018509]

Calling on light. Activated from the front cab by the driver's key to indicate to a train following that the train driver needs assistance and it is safe for the following train to pull up close behind if signalling permits this to be done safely. The light illuminates in leading and trailing cabs.

[1018509]

Further to above these lights were fitted from round about the 1967 stock and to all stocks that didn't already have them on refurb.

[Flying Pig]

Interesting this. They do things very differently down the tube compared to how we do it in big trains. My only experience of driving sub-surface lines is on the Northern City Line. Here also it is assumed that the driver of the failed train won't be able to get back down the train to meet the 'assisting' driver at the assistance point, as we would on the mainline.

But it is expected that prior to coupling up and carrying out assistance, both drivers will be able to talk directly to each other by way of tunnel phones clipped onto the wires (as well as via the radio link to the signaller).

FP

[1018509]

On the Underground the fitting of calling on lights was a pre-Connect Radio project. I think this radio system will see the end of calling on lights, although the fact that the light is illuminated is an indication that the train will not move as the light is operated by the same key (which is locked into the calling on light switch when the switch is operated) as is required to move the train