Roads to power green cars on the go

Today’s Times reports on the fascinating trials being carried out by the Highways Agency and the engineering consultancy Halcrow into wireless charging of electric cars.

http://www.thetimes.co.uk/tto/business/industries/transport/article4331618.ece

We’d like to see this go further;  why could motorways and main roads not be used for electricity generation ,  with canopies of PV running the length and width of the road.  The energy would be used at source for charging cars and the drivers charged per mile which would,  in turn,  pay for the roads.