Lowering the limit on A roads makes no odds...
The A140 is a case in point, it runs straight from Norwich to Ipswich. They dropped the limit 40/50 along most of its length, along with no overtaking zones and a smattering of cameras a decade or so ago, yet people still kill themselves on it with regular monotony

these are mostly people taking a chance when turning across the traffic into/out of one of the many side roads
Only way to make it truly safe would be to build a roundabout every two miles, with a central armco barrier along its entire length allowing only left turns.
The rural 40 limits around here are unenforced as the police didn't agree to the lowering of them, arguing that it was always the drivers responsibility to drive to the road conditions and ensuring that they could stop in the visible available distance.
Obviously if you hit a pedestrian or cyclist at 80mph around a blind bend or crest, then you deserve to be put on soap duty

If people seen a speed limit on country roads as just that, a LIMIT! Not a target we wouldn't have to lower them.
They're not targets, they're rough approximations of what some gimp in an office twenty miles away thinks might be a good idea...
If the roads were better designed then they wouldn't need to keep lowering limits in the name of safety... and the first person who suggests that it is in the name of the environment will be awoken at 3.30 am every school night by a big diesel V8 at full chat
