On 09/10/2012 00:50, Steve Fitzgerald wrote:
In message , "
writes

The illuminated speed control sign is just an illuminated version of a
normal PSR sign used in tunnel sections.

Really? I have seen speed signs that are not illuminated from behind,
but rather from above by an external lamp. The ones that I initially
referred to were illuminated from behind and had white numbers on a
black background.

The speed restrictions that are illuminated by an external lamp have
black numbers on a white background.

I also notice that the speed restriction signs illuminated from behind
are around areas where there could be policemen or junctions.

I'm not familiar with the Northern line but I can ask the question of
some colleagues who should be able to clarify.

That would be nice.