I work in the transport industry (consultancy though) and I specialise in motorway traffic.

Much of my work is to do with smart motorways, mostly design and post-opening evaluation, but other crap as well - mostly writing plans to limit disruption in the construction phase that are then totally ignored my the project team despite having spent tens of thousands on them... yay, great fun.

Firstly it should be pointed out that not all smart motorways have their hard shoulder removed. That seems to be a general consensus, and in fairness most smart motorway projects are all lane running, but smart motorway does not inherently mean all lane running. There are a few types of hard lane shoulder running as well; All lane running means it's only a hard shoulder when required and Dynamic Hard Shoulder where it's only used as a running lane when required.

I appreciate it's a dull point to make; but it's an important distinction given it's the area the debate about smart motorways focuses on so often.

For the record I am totally against use of the hard shoulder at all. I've worked on post opening project evaluations which require you to analyse masses of raw traffic flow data against how the 'smart' bit of the motorway is functioning. The amount of people driving in the hard shoulder despite Red X marking the lane is genuinely mental. Like I appreciated it would be a problem, but we're talking hundreds of vehicles making the mistake per day on some stretches I've worked on...

As ever the advice is; Do not sit in your car on the hard shoulder if broken down, running lane or not, ever. Get out of your vehicle, on the passengers side and get yourself over the barrier onto the verge. That barrier is the difference between being killed if hit, and walking away. A number of contractors on a project I am involved with died by not taking the get out of the passenger side advice recently.

What do I think of them generally though?

In theory they are an excellent way to increase capacity when building isn't an option (and building isn't an option even when space allows). The issue is, theory and how humans behave aren't the same thing at all. I personally think all motorways should be smart motorways while retaining the hard shoulder. When they work, they do work well. The idea that traffic management can be automated is incredibly useful as well.

Whether the value for money adds up on even the current projects... I'm not so sure. I think they are a stop gap solution to a problem there is increasingly no viable solution for, there are smart motorway schemes about to hit the ground that are going to be over capacity on open for traffic day.

Highways England know this, the DfT knows this.

But building more roads does not solve the problem, we've been doing that (by we, I mean across the world. We've not been doing it in the UK...) across the world only to see the same problems pop up time and time again. Building more road space does not improve traffic flow in the mid to long term, it just compounds the issue and prevents sensible travel behavior cultural change from taking place.