As far as I am aware Vehicle to everything - V2x at the moment is really just tests of roadside Wifi or telephone mobile data, and will first be used for collecting tolls and so forth. I suspect as soon as it gets used to record time of transit data, odd hacks will appear to modify the time stamps so your speed over ground is not so easily deduced..

Mike.

Most lorries and some taxis are fitted with electronic loggers which record time, speed and GPS location.  If these figure were transmitted to MofT then spying on everyone would be possible but not beneficial as it misses the main cause of accident which is tailgating and not keeping within safe braking distance.

It was a bit more than tolls - here you go: Connected car testing goes live in Coventry as part of UK CITE Consortium | Coventry University

Unfortunately it looks like the funding run out and this is no longer active.

Like Mark Tickner above, I tend to trim my speed, particularly in average speed zone stretches using my sat nav.  I have also checked the speedo on my VW, which matches the smiley face signs and sat nav at 30 mph, and also suggests that speedo 70mph is sat nav 63.

I travelled today from West London to Devon via the M3/A303/A30.  The M3 smart motorway stretches worked well, traffic running smoothly although quite heavy, and I felt safe.  Four of the emergency laybys had broken down vehicles, two being attended by breakdown services.  Where I did feel unsafe was a non-smart section where at 65mph (sat nav) in the inside lane a very heavy lorry tailgated me, to the extent I took steps to get behind it; also in a single carriageway section of the A30, in a line of traffic travelling at 40mph, a Range Rover insisted on tailgating.  In my view it is poor drivers that cause the trouble by not driving according to the road conditions, whether or not the technology is working.  Using technology to try to correct it will fail at some point.