owen b wrote:
Here's something I thought up having made a trip through Bath recently
It's a nice map, but surely there's several problems with doing a Bath bypass in isolation :
i) you'd encourage use of the A36 as a long distance through route, so you need to resurrect a plan to upgrade all the way to Southampton, otherwise you dump even more traffic onto inadequate sections of the A36 further south
ii) other routes south of the M4 between the M5 and A34 are mostly poor or worse, so any decent new route is going to attract traffic diverting from poorer routes (eg. A37/A362 traffic south of Bristol might divert to the A4/A36)
iii) surely a through route to the M4 (ie. a Bath eastern bypass) is a higher priority than a south western bypass - I don't think a south western bypass would relieve Bath very much
iv) money, environmemtal issues, very up and down topography etc.
On the whole though, the section running out of Bath is by far the worst section of the road in terms of design, and the speed that it can be taken at, so if there were to be some form of improvement to any part of the road, I would personally say there is the best place to do it.
You're right about attracting additional volumes of traffic from other routes though, but then again, that shouldn't really be a reason to not upgrade a road, it's just something that needs to be taken into consideration with the design. The long stretch of D2 would not only provide additional capacity but allow for safe overtaking of slower vehicles where currently that's incredibly difficult.
About the usefulness of the bypass in relieving the centre from traffic, I'm looking at from the perspective that A36 traffic has to go through the entire city and out the other side, whereas north-south traffic just has to loop round over the river. A northern bypass would provide a similar benefit to the new A36 route as that traffic has to fight through the whole of Bath as well, but I'm not sure how much use that would get.
A simple fork off the A4 starts the new road off, and access is provided in the opposite direction via a half-diamond junction with the A39 shortly after.
Doesn't seem particularly necessary to me, as the road is S2 to the northwest, a large at grade roundabout should suffice.
If grade separation is required though just go with the traditional roundabout interchange and have the A4 TOTSO. Then you might as well turn the other two roundabouts into roundabout interchanges as well.
Not a bad idea, and if you threw in an A4 bypass of Saltford with it connecting up to the roundabout at Keynsham as well, you could have continuous D2 from the Avon Ring to right around Bath!