Probably like many initiatives in the business world, the trial was made to work, usually by its sponsor micro managing the trial with lots of resources and the wider adoption cherry picked bits from the trial.
I'm sure I read or heard on the radio the number of emergency refuges was significantly reduced in the full implementation.
When so many are killed and injured on the traditional hard shoulder by wandering motorists it does make you wonder!
AFAIK there was only one study (on the M42) and when the intervention was implemented elsewhere:
The sequence of events and the report are in the Wikipedia page. (Although the M42 report isn't in the format that I remember.)
I don't read it like that.
That way of working led to the AA and the Parliamentary Select Committee becoming the effective quality control mechanism. That's a lot better than nothing, but it's not appropriate for something as important as this.
But we don't know that even as implemented the intervention increased collisions or deaths or injuries. It was certainly associated with some that were dramatic but perhaps it reduced more that would have occurred with the higher vehicle density if the intervention hadn't been made.
Usual simple message: if something's important we need evaluation, preferably independent, and publication.
Democratic dissent is not disloyalty, it is a positive civic duty
Feel sorry for the guy on the (live) M6 smart motorway (junc 3 to 4) who broke down in his brand new looking lambo. I bet he was $hitting bricks as he ran to the emergency phone! He was in nearside lane but the lorries were thundering up to it!
When passing on return home, Highway Patrol had coned the lane off and lambo unmarked Phew!
Not very smart if you ask me!!