Re: Can they do something more useful instead?
Since when has winter tyre and snow chain legislation existed in the UK?
That is my exact point. About time to introduce it. While there is no point making it mandatory for everyone, enforcing it specifically during warnings so that people heed the weather warning should do the job.
As far as the legislation it does exist. The definition of "roadworthy vehicle" is up to the court and IS dependent on the actual road conditions. There is precedent - plod can start handing out tickets for "non-roadworthy vehicle" because you took a car in summers out on a road in the middle of a blizzard. The last time it was done by either Lancashire or South Yorkshire about 12-15 years ago (cannot remember, it made the beeb - you can find it). All tickets were upheld in court.
However, instead of doing it once in a decade (and only when they get annoyed) it is better to codify it and get it done once and for all. If the met has said orange and you are in summers you really do not belong on the road. You are endangering everyone.