In message .com, at
04:18:50 on Tue, 26 Jul 2005, Earl Purple
remarked:
Often caused by a bad junction, usually one with 2 traffic lights close
together. The second light is red far too long, and so traffic from one
phase of the first light fills up all the available space and traffic
from the second phase can never move.

I've seen that in Central London.

A junction on a one-way street where a road joins from the left.

The road ahead fills up with traffic emerging from your left, and
there's no gap between the rear of the last car to emerge, and the box.

The traffic then sits there, stationary, all the time your light is
green.

Just as it starts to move, and leave you a gap to escape into across the
box, your light goes red.

The gap then fills up with traffic emerging from your left.

Rinse and repeat.
--
Roland Perry