"SamB" wrote in message
oups.com...

"Is there are difference in the altitude of the
two roads as they approach the junction?"

Yes, there is. Undercliff Road heads downhill,
and Halesworth Road climbs quite steeply upwards.

Thanks, it should have been obvious, because the other place I can think of
where two roads run needlessly parallel (when viewed on a map) is in Erith,
and altitude is certainly the reason there.
http://maps.google.co.uk/?hl=en&f=q&... 1351,0.002494