Umm, does anyone think fixed speed cameras are the ideal solution? Particularly when they are painted yellow - that was introduced to appease the motorist lobby; there wasn't any research into whether it would help matters or not. The fact is, it wouldn't. They only affect vehicle speeds for a short distance after the camera, because they're so easy to spot. Research into visible vs stealthy cameras conducted in New Zealand showed an 11% better reduction in deaths with covert cameras.
Average speed cameras were introduced near here on the A14. As ChrisS pointed out, they've made a huge difference. Compared to the fixed cameras which they replaced, they've shown a large decrease in serious road accidents. And they have made the road far easier to drive along if you are sticking to the limit since the spread of vehicle speeds has reduced dramatically. It's better for the environment, it's safer, and it works. Average speed cameras are the way forwards.