We've covered this subject many, many times, but always with the same conclusions.
The key one is that UK governments are only prepared to discuss speed limit reductions, our roads bearing witness to this. Over very large areas now 60 mph zones have all but disappeared, the former 50 limit is defunct, and reduction from 60 being straight down to 40 or even 30mph.
And in huge swathes of cities and towns we now have 20 mph limits. My own borough, one of the largest in the UK now has the borough wide 20 limit on all but a few major through routes. That alone is a killer for any suggestion that e-bikes could be permitted 30 mph, given that most commuting is in urban areas.
The DfT have voiced fierce opposition to any suggestion of adopting the 28 mph S class of e-bikes, and they aren't alone in that. Germany in the EU had it first in a registered form, but since only the Netherlands have adopted it in a limited form. France thought about it for 2017 but has now not gone ahead and no other EU nation entertains it.
There's also recent legal obstruction like our introduction of the Q group driving licence, and that would apply to any 30 mph e-bike. Such bikes under our laws would also have to be registered, number plated, third party insured and new riders would have to carry L plates and go though the CBT. All riders would have to wear motorcycle approved helmets, that would have to be when 30 mph moped riders have to wear them.
Finally your arguments for adoption of 30 mph don't bear examination. The halvings etc you speak of assume millions of drivers abandon their cars and take up cycling. That's never going to happen in our car culture, even bicycle hating country.
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