, my own experience matches Michael’s
One key aspect of active traffic management doesn’t appear to have mentioned so far, i.e. it only ‘kicks’ in at times of high traffic volumes.
Having (successfully) campaigned against the M1 widening back in 2006 (see <http://herbeppel.blogspot.co.
uk/2006/11/30-october-2006- eventful-day.html>), I can safely say that the active traffic management that was subsequently introduced on some of the M1 sections, mostly without any actual widening, was certainly a good compromise, compared with the utterly mad alternative of actual widening to build additional lanes!