"Road safety in Scotland is at a critical time. National statistics indicate that collision on non-built-up roads (roads with a speed limit of 40mph or higher), account for over 40% of the total number of reported casualties. They also account for 66% of those killed and over 40% of the total number of seriously injured.”
As usual, a sledgehammer to crack a nut. Nothing in that statement says that excessive speed is the cause of these fatalities. For all we know, it could be collisions with deer wiping out the locals.
If speed is a factor, is it speed over the posted limit? If so, then the requirement is for effective enforcement, not lower limits. If drivers/riders are prepared to travel at 80mph in a 60 limit, they'll still do it if limits are reduced to 50mph. It's just the statistics will alter to show the errant road user is now 60% over the speed limit instead of 33%.
However if folk are crashing below the posted limit, then its time to review those limits. But that takes time, effort and brains to work out, not something politicians have much of, it seems.
Just take a ride around Wales, you can tell the local drivers quite easily as they are the ones ignoring the 20mph limits knowing there's no-one around to enforce them.