The idea
The motorway speed limit restricts freedom unnecessarily when traffic is not heavy. Cars today are far safer than when the 70 limit was set, and the number of people killed and injured on motorways is much smaller than on other types of road, however you measure it.
A limit of perhaps 90, or even 100, would make more sense. Needless to say a pilot would be sensible.
Why is it important?
The value of time saved would be large
It would end a law that is rarely respected – in general laws should either be enforced or abolished.