Michael Bell wrote:
In article , John Rowland
wrote:
"Michael Bell" wrote in
message ...

Junction 8 on the M1 was designed "wrong way round"
in Mrs Castle's time to test the idea of designing junctions
so that they could be changed over to right-hand drive,
but the experiment was never repeated.

In what way was it designed the wrong way round? Just wrong
gradients and curvatures?
[snip]

It is a normal "trumpet" interchange where a non-motorway road
joins a motorway. Where any road crosses another, driving on either
side of the road, before the non-motorway road crosses the
motorway, there are two slip roads which can be filled in simply.
But when the non-motorway road has crossed the motorway, its two
carriageways are the wrong way round to join onto the motorway.
In a normal British trumpet interchange the left carriageway turns
270° left and under itself to join onto the motorway and the lane
coming off the motorway turns off the motorway well before the
junction and makes a wide sweep round. In the case of this
interchange, when you come off the motorway, you first pass under
the bridge and then make a sharp turn left. It's a route I do about
once a month, and it is easy to see you might try to get round too
fast.

Michael Bell

Normal British Left-hand layout :-

[garbled diagram snipped]

Far from scale, but I hope you get the idea.

Not sure how you constructed that, but the lines are all over the place
on my screen. If you're going to post diagrams like this, please use a
fixed-width font like Courier New when drawing them and avoid using
tabs. Even if people don't normally used a fixed-width font, they can
switch to one to see the diagram, and it will look right. I think you
meant something like this (view in fixed width font):


/----------\
/ \
/ /----\ \
/ / \ \
/ | \ |
/ | | |
/ \ | |
/ \ | |
--------------------| |---------------
Motorway | | Motorway
--------------------| |---------------
\ | | /
\ | | /
\ | | /
\ | | /
\ | | /
\ | | /
\ | | /
\ | | /
\ | | /
\ | | /
\| |/
| |

The actual junction 8 on M1 is a mirror image of that.
See http://www.learn-it.net/images/hemelm8.gif
It is certainly not unique. J.7 of M4 is similar. It seems more
likely that land use and contours determined the design.

--
Richard J.
(to e-mail me, swap uk and yon in address)