Spot on Matt.
Put as many speed camera's as you want everywhere and you won't reduce accidents, in fact they are likely to go up. This is not just my worthless opinion, it is based on factual reports from the TRRL. Speed Kills is the most misleading tag line I've seen in the governments misinformed strategy to reduce accidents. Of course speed kills, as somebody has to be moving in order to injure themselves or somebody else, but the perception and the knee jerk "safety" camera policy infers that speeding kills, which is not borne out by any of the actual research. For anyone who's actually interested in factual information rather than naive schoolboy opinion, serious accidents where speed was a contributing factor is less than 7% and this figure is skewed as it includes joy riding, police chases etc.
Nobody is going to criticise the placement of speed camera's at accident blackspots, not because they reduce speed necessarily but they do temporarily focus the mind of the driver on the speed, conditions and possible hazards ahead. But to extend this logic to every dual carriageway and especially motorways is just patently misguided.
Speed does not cause accidents on motorways. HGV's and inattention cause accidents on motorways and if everyone drives at 70 on a busy motorway then you've got more vehicles on the motorway at any one time and you'll increase the inattention as drivers slip into a trance because they're not required to really participate in what's going on.
The other issue is the indiscriminatory nature of the speed camera which doesn't take into account the type of vehicle or the conditions. So the HGV doing 60 in heavy traffic in the rain is classed as safe, whereas the car doing 85 on a perfectly clear day & light traffic is not. I know which vehicle will be able to brake safely should something happen up ahead.
Also the latest breed of camera's are all front facing (Truvelo & SPECs) so ignore the biggest victim of death on the roads, the motorbike.
So to say the theory is flawed is a massive understatement, use the technology to get the drunks, druggies, uninsured, unroadworthy & the incompetent off the roads and you'll get support, but to support a policy of penalising every motorist on the off chance you'll catch one that's dangerous is naive beyond belief.