There's been a big investment in the UK recently in "smart motorways" http://www.itsinternational.com/categories/detection-monitoring-machine-vision/features/u

There's been a big investment in the UK recently in "smart motorways" http://www.itsinternational.com/categories/detection-monitoring-machine-vision/features/uk-defaults-to-hard-shoulder-running-to-expand-motorway-capacity/ http://www.itsinternational.com/categories/detection-monitor... https://www.rac.co.uk/drive/advice/driving-advice/smart-motorways/ https://www.rac.co.uk/drive/advice/driving-advice/smart-moto... These have overhead screens which show the speed limit (it's variable) and whether each lane can be used. They also have a lot of speed cameras enforcing that the displayed speed limit is being followed. The intention is to keep traffic flowing at a much more consistent speed to avoid bunching. It also means if something happens traffic can be slowed down many miles away. It essentially means the same road can have 30% greater capacity.