(09 Jul 2014, 8:52 pm)Dan wrote Let's not forget that the white roller blinds on TfL vehicles and Lothian Buses vehicles will all be lit up at night, and hence could be argued as providing white light.
Operators up and down the country have white rear destinations, so there must be a workaround to this alleged "law", because as I've said previously, those who manufacture these destination displays just wouldn't do it if it meant that bus operators were going to turn around and have to replace them. I also doubt that bus operators would incur the additional cost of buying white opposed to amber if they had even the slightest incline that it was illegal and there was a chance they'd have to remove them - not only would it tarnish their reputation, but there's also a chance that the manufacturers wouldn't refund the difference.
Its not an 'alleged law'. Stop being arrogant about it. You asked the question and you got an answer. Look up the The Road Vehicles Lighting Regulations 1989.
Section 11, Point 2, Subpoint G quotes;
No vehicle shall be fitted with a lamp which is capable of showing any light to the rear, other than a red light, except–
(g)in the case of a bus, light for the purposes of illuminating a route indicator;
This may allow use of white lit destination screens at the rear, but it does quite specifically state that light for purposes of illuminating a route indicator (in the case of London rollerblinds). It makes no mention of the white light being the actual route indicator.
Its open to interpretation and as already suggested, it may only take one very particular vehicle examiner to decide said vehicle is not conforming to regulations.