"Andy" wrote in message
...

But don't the Electrostars have the cameras on the train, so there is
no transmission system needed, other than feeds into the train's own
systems.

You can see the cameras down the side of the train in this image:

http://www.railfaneurope.net/pix/gb/...377-432-mt.jpg

The Northern and Central lines are more complex of course, there
probably isn't space for cameras on the side of the cars.


But technology can allow for smaller cameras and easier installation, can't
it?

Retractable mirrors can also be an option in some places, though granted
they might not be effective everywhere on LUL.