https://www.dailymail.co.uk/news/article-13096425/Smart-motorway-computer-glitch-six-car-pile-M6-failure.html
Smart motorway 'computer glitch' led to terrifying six-car
pile-up on M6 after ENTIRE safety system shut down in a
'catastrophic failure', insider claims
. . .
They've been wanting to implement these in parts
of the USA too.
"Smart" systems just aren't that damned smart - not
yet anyway, not for some time to come. Bad as they
can be, human drivers with human intuition still
do better than automation.
I'd suggest another kind of "smart" - Informational
Systems - that can tell human drivers about hazards
and slow-downs and such far enough ahead of time
to be worth it. They exist in some urban areas,
but tend to update too slowly and/or fail to
provide enough details. Fog/Ice-prone stretches
of highway warrant electronic sensors and VERY
prompt updates.