"iantheengineer" writes:

How much delay depends upon the designer and the type of control,
whether it is fixed or adaptive. All modern schemes are adaptive,
MOVA, micro proceesor optimized vehicle actuation is now the
standard method of control for isolated junctions

When the traffic lights at Chiswick Roundabout were upgraded last
year, tailbacks on the Eastbound A4 quadrupled. The "optimized"
controller was routinely letting the southbound North Circular traffic
onto the roundabout at the same time as the eastbound A4, with the
result that only 3 or 4 cars from each lane could get off the A4 on
each cycle. I am not convinced that MOVA lights are an improvement on
the fixed cycle synchronized lights that started becoming popular 20
years ago.