This plea is from a hobby group, it's not government policy.
And it wouldn't work in any case as it's not possible to drive for any length of time at less than 10mph.
What we actually need in the UK, which is normal in many other countries, is a Jaywalking law. That would save many more lives and significantly reduce pedestrian casualties. The law should be that it's illegal (punishable with significant fines, like other countries do) to cross the road anywhere other than dedicated, marked pedestrian crossings. Step off the kerb and get hit by a car, the pedestrian is legally at fault for the accident. That law would have a dramatic effect on road safety, and make people switch the fuck on.
Instead we have hoards of zombies, iPhone in one hand, Starbucks in the other, with headphones on and their eyes locked on their phone screens, blindly wandering into the road without so much as a glance to check for approaching bikes or cars.