Coal the reason for design of junction
YOU ask in your editorial column (March 9) "When it was created had the road designers of the day never heard of ramps, underpasses or flyovers?"
As one of the designers who worked on the original scheme, the preferred alignment at Sheriffhall was a grade separated junction similar to all other junctions on the City Bypass.
However, there is a geological fault which crosses the bypass at this location and at that time the Coal Board objected to any form of grade separation – either flyover or underpass.
If road subsidence occurs as a result of collapsed mine workings, the roads authority can make a claim towards the cost of remedial regrading work, but the Coal Board stated at that time that it would not consider any claim where there were structures involved and would lodge a formal objection at the planning stage.
In any case, constructing bridges at or near a fault line in an area of active coal extraction would have been an unacceptable risk.
Therefore the only option available to the designers was an at-grade junction. So please, don't blame the original road designers. The irony is, of course, that coal extraction has ceased in that area.
Bob Thomson, Silverknowes Gardens, Edinburgh
Moderator: Site Management Team
Some of my historical road investigation has led me down the geology path for Scotland since it's obviously fundamental to engineering what lies beneath our feet. Edinburgh has some interesting volcanic history right through to the Bathgate hills (Dechmont Law, Cockelroy and the Bathgate Hills), I found this map which is consitent with the fault line mentioned above: