In message , at 23:13:20 on
Sun, 3 Oct 2010, John Salmon remarked:
While this is true, the road signs should show both numbers with the
"secondary" route in brackets to show that one can be reached by a
turn off the other. This is the general convention in the UK for all
such cases. A case I saw recently is near Colchester, where the A120
to / from Harwich crosses the main A12. Both roads share the
Colchester by-pass and the road is shown as A12 (A120), with the
first junction you encounter with the A120 shown as A120 east or A120
west to help those on the A12 know which one they need to turn at.
There are some examples of poor signage where roads merge and then
separate. The A57 - the main route from Lincoln to Sheffield - merges
with the A1 between Markham Moor and Apleyhead, but drivers approaching
Markham Moor from the Lincoln direction are given no clue whatsoever as
to the correct route to take, and it is not at all obvious. The A57
just disappears.
I don't think the brackets indicate a merged route. They simply say that
"if you take this route you'll eventually get to the bracketed road".
Sometimes that'll be because it de-merges, but it's just as likely that
you'll have to take several turns. An example near my house is this one,
where the road to the right is neither jointly the M1, nor does it
demerge into the M1 (which is actually 10 miles *behind* the camera).
What the sign (on the A6011 at this point) is saying is:
Straight ahead is the A52, which eventually crosses (at right angles)
the A46.
To the right is also the A52, which eventually crosses (at right
angles) he A606; and also to the right (a long way and many
junctions) is the M1.
http://goo.gl/maps/P703
This is consistent with your observation at Markham Moor... the A1 is
not intended to be a road "merged with" the A57, the latter road simply
stops there. Go north a junction, and there are signs pointing north
saying "this way to Doncaster on the A1, and incidentally this leads to
the A57 for Sheffield and Worksop"; but the one pointing south is just
A1 Newark/London.
http://goo.gl/maps/pMGR
Slightly to the north, this sign doesn't even have a (A57) for Lincoln:
http://goo.gl/maps/3VxV
--
Roland Perry