This idea was inspired by my old dad telling me that the M25 was backed up because of a blockage in the M1, causing me to think how you could store cars wanting to go onto the M1 without blocking London's ring motorway.
Essentially this is a giant Ferris Wheel with garages instead of seats at the
spokes that is placed on the motorway or it's entrance. People drive into the empty garage before them and them it moves clockwise, presenting another empty garage until the reservoir fills up. The garages stay the same way up, just as the London Eye does, to avoid people falling out of open top cars ...
Once the first reservoir fills up another can be placed in front of it, allowing more car storage capacity.
Obviously you would place these reservoirs using a fleet of airships or flocks of giant geese, whatever has the lowest feed bills ...
This is the first idea I've had which has been inventive enough for the Halfbakery for sometime and I even checked the Car section for possible redundancy.