You are on the right tracks with what you say about traffic. In the immediate area to the Asda store, there will be more movements, of course there will. But can Hibbert Lane cope? Probably, its nice and wide and it is, afterall, one of Marple's 'main roads'. Its all very well for people on Stockport Rd, Station Rd, Church Lane & Hibbert Lane to cry foul about potential increased traffic on routes, but thats the risk you run living on a 'min road'. Marple as a community cannot stand still, it must develop and regenerate and in this car obsessed world, I'm afraid that traffic is a by-product of any 'progress'. To complain about it (and this is not aimed at you Simone, just a general observation) is often a shade hypocritical when nearly all of us merrily drive a car wherever we want, with scant regard to the people and properties we pass. And I say this as someone who lives on one of Marple's busier roads.
And this is nub of the arguments on traffic at the Asda site for me. I have some sympathy for the point they make that it is very likely that most of the town already shops at a supermarket at least once a week and given the lack of choice, its pretty certain that this involves a trip down one of Marple's main roads and out of the town (most likely Stockport Road). There is therefore a good chance that the 'net' impact on traffic in Marple as a whole will be relatively 'neutral'. What Asda need to do is sort out the local 'hot spots'. How they achieve this will be the key, as it won't be easy as space is limited. But we can't bury our heads in the sand and pretend that supermarket shopping related traffic isn't already a problem in Marple or at the very least is something that we, as a community, seem to be happy to 'export' to Bredbury / Hazel Grove, Glossop, etc. MIA's estimates of traffic flow are probably a decent estimate, but the big question is, how many of these are will be 'new' to Marple, and how many will simply be a diversion of those who were previously on a trip out of the town to an existing other store? My guess is that it will be a very substantial number and I'm sure that this is something that Asda will give us 'chapter and verse' on, within their planning application.
I would suggest that a "pollutive nightmare" is a bit of an over-statement. National guidance on traffic related environmental impact illustrates that changes in traffic flow result in relatively small changes in pollutant levels. Normally you wouldn't expect a material change in pollution levels worth looking at in detail until you get a 30% increase in traffic movements over and above the base.
Its a tough nut to crack and I wait with interest to see what Asda propose. It will be one of the key issues that will inform my own decision as to whether I will man the Marple barricades or not.