Speed Strictly Limited

Some of you may well recognise this very busy stretch of elevated motorway  as the M5 wends its way through the Black Country in the West Midlands.  There is a lot of work going on underneath the motorway doing all sorts of maintenance work.  I might go and Blip it one day!  This stretch of the motorway is limited to 30mph but it is relatively short fortunately.  The worst part seems to be the lead up to the restricted section where the shuffling into two lanes takes place.  I suppose those who study traffic flow will be able to explain the logic of that...