Junction 23 on the M25 in Hertfordshire is the single biggest gyratory on the whole of the National Highways network. At about 1.2km in circumference, the junction sees some of the highest traffic flows on the M25.
Junction 10 is the busiest section of the M25, with over 270,000 vehicles travelling through it every day. Due to the volume of traffic and the resulting queues, this area of their network has a very poor safety record and holds one of the highest collision rates across the National Highways network.
Gravelly Hill Interchange is the UK's busiest motorway junction and is one of the country's most iconic concrete structures which turned 50 last year. The winding labyrinth of roads along the M6 is also one of the biggest motorway interchanges in Europe and more than 200,000 vehicles travel on it daily.
Answer. Answer: A motorway just relates to the A road that it's relieving pressure from. The reason there is no M7 is that the A7, which runs from Carlisle to Edinburgh has no need for a motorway to relieve it.