Another big one today at East Ilsley. Nightmare for us around here. There are essentially three key roads feeding the down lands - the A34, the A338 and the B4494. When the A34 is mashed, traffic diverts to the other two - neither of which are designed for this level of traffic and all of which get bottled up towards Wantage or through the narrow Downland roads.
It seems that because its on the border of Berks and Oxfordshire, no one takes responsibility - or only takes it on 'their side'. I can't find any evidence that west berks and oxfordshire have sat down independently or together to fix the problem or raise the issue with the Highways Agency. Can't help thinking that the Tories in West Berks won't do anything about it because they rely upon voters in the 'bmw' classes who I see regularly breaking speed limits for fun and often causing these very problems.
Not helped I'm sure by two different fire and rescue services, two different ambulance services etc - and now that their budgets are squeezed they are not even prioritising proactive or pre-emptive activities.
The effect on the Downlands is mostly traffic - speeding traffic and the pollution they cause racing through our narrow lanes, disrespecting our local communities with anti-social panic driving as they try to get back on their original route. My year living in West Ilsley was hell - traffic hell. You've no idea if you going to be able to get out of the drive way, to school, works or the shops, and certainly no way of knowing if your kids are safe cycling in the village. This must be a nightmare in East Ilsley. Great Shefford is often hit too with cars racing down the A338 diverting around the A34 accidents.
Personally I think there should be a 50mph zone from the M4 to the Oxfordshire border, and it must be monitored by average speed cameras (the only thing drivers seem to respect). By doing so, I recon 99% of all the accidents on that road will go away, the traffic will flow more timely and the Downlands will be spared the anti-social driving of the panicked drivers searching for a diversion.

Have you considered - given that motorways and dual carriageways are generally the safest roads in the country - that there might be a specific problem with road design (like the dangerously short sliproads at the A34/A4 junction)? Unlike ill-considered speed limits, design improvements would actually improve safety instead of turning drivers into unthinking speedo-watchers.
I'm betting most of the problems are caused by the speed differential between the lorries crawling up the hills at 30mph and the speed freaks doing 80mph+. I have even been caught up between two lorries one doing about 30mph and the other overtaking doing about 33mph. Whilst the initial panic breaking may not cause an accident, around the bends and sweeps of the A34 visibility is limited and a combination of the ripple effect of panic breaking and speed usually catches someone out.
Not sure a week has gone by in the past year when there hasn't been an accident at or near East Ilsley.
Would be interesting to understand how you think speed is not a factor. Even the problem of the shorter slip roads would go away at a a lower speed.