It seems to me from what you are saying is that its very hard/ impossible to enforce any of these laws? Or am I misunderstanding what you are saying?
If there is no way for police to test the bike, then how is it possible for the DfT/Police to prosecute for an offence that is over 250w, assist speed limit etc.
That correct. The law on pedelecs is complex and police officers rarely have any idea what it is. A few traffic officers have a little knowledge, mainly because some forces have tried out or even bought some pedelecs for police work.
Another problem has been the confusing mixed messages UK police forces have received from the DfT over the years, resulting from the following facts:
From 1983 to 6th April 2015 the EAPC regulation assist limit was 15 mph and only 200 watts was permitted, though that could be throttle controlled.
However, in parallel to that, from 10th November 2003 up to date, the Type Approval regulations permitted 250 watts and 15.6 mph, but banned throttles.
How can anyone, let alone a police officer, make any sense of those two between 2003 and 2015?
To complicate things further, the great majority of pedelecs sold from 1999 onwards were 250 watts rated while the EAPC law that the police followed stated the limit was 200 watts. That eventually lead to a couple of attempts at prosecution, but they failed when overruled by the DfT, probably through embarrassment.
Which gets us to the funny bit:
If asked during the 2003 to 2015 period what the law was, the legal department of the DfT would say 200 watts and 15 mph.
But the Vehicle Inspectorate department of the DfT would say 250 watts and 15.6 mph.
Those were because the legal department used the EAPC regulations and the Vehicle Inspectorate used the Type Approval regulations!
You can probably understand now that even if a police officer knows anything of this, they are likely to regard it as a hot potato best avoided. There's no shortage of much easier arrests.
Of course if someone rides an e-bike that's being sold as and possibly even marked as capable of greater than 250 watts and/or faster than 15.5 mph assist speed, the police can and may act, since that makes prosecution easy.
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