Sorry to hijack, a question for GTRGeoff.....
If in a far away land, a motorist were to be caught by a fixed camera on the reverse side of a bridge doing 7km's over the limit, how can this speed be acurately measured as this motorist tells me there are no lines on the road indicating distance measured etc nor which lane the camera was focused on as there were 4 (potentially any of the space craft travelling in any lane could have commited said offence).
Any thoughts?