While I am inherently opposed to the idea of motorways without a hard shoulder (I shredded a tyre a couple of months ago on a single-carriageway "A" road, fortunately without much traffic about, and was grateful I wasn't on a "smart" motorway at the time), I note that if you travel on the (non-"smart") M54 motorway towards Shrewsbury, after you have passed Telford it segues seamlessly into the A5 dual carriageway, and the latter does not have hard shoulders, despite being for all intents and purposes a continuation of the motorway with the same speed limits and traffic levels. I suspect that there are plenty of other dual carriageways dotted around the country with the same speed limits as motorways but no hard shoulders, and they seem to manage alright without radar spotting stationary vehicles. I suppose the problem is that, by definition, "smart" motorways have heavy traffic flows, hence the desire to make use of the erstwhile hard shoulder to provide more capacity.
Richard Greenhough ● 2015d