
Been thinking about something like this for a while, but as always, in practice what seems like a good idea...
Tripod not quite tall enough to get the camera over the bridge railings, so had to shoot through the bars, which limited angle and how wide I could shoot. Bugger to focus as well, as the road surface itself is too dark to ge a lock on and the cars are obviously travelling a bit to fast to get a reliable point on. In the end manual focussed on one of the white lines and then locked it.
Also had to cope with a) busy-body PCSOs interrogating me on what I was doing and b) gangs of chavs trying to interrogate me on what I was doing.
Experimented from 1 sec all the way up to 30 secs. 30 secs too long in that light and for traffic that speed - in my opinion. Light trails too dense and surroundings too lights.
Top my favourite (f8, ISO 200, 5 sec, 16-85@85mm), but below was a close run second (f8, ISO 200, 15 sec, 16-85@58mm). Too busy I think.