Michael Hoffman wrote in message

Solid green means that non-emergency vehicles may not legally cross the
road you are on (although they can turn right/left on red).

Are you sure about that ?

In Brentford, where the A4 joined the Ealing Road, the traffic
signals were arranged so that two conflicting flows would both
get a green simultaneously. This was some time ago and it
was the first I'd ever seen. I don't know how common conflicting
greens are.

A green doesn't mean that you *CAN* go; it just means "go if
it's clear" (i.e you should behave (when green) as if there
were no traffic sig there at all, and only proceed if you could see there
was no oncoming traffic)

Richard [in PO7]