It's bad enough having idiots driving normal cars around but having idiots driving cars around with half the windows obscured is even worse!
Can those cars legally be driven like that? Hmm, maybe not ...
Regulation 30 of the Road Vehicles (Construction and Use) Regulations 1986 (SI 1986 No. 1078
as amended) requires that:
(1) Every motor vehicle shall be so designed and constructed that the driver thereof while
controlling the vehicle can at all times have a full view of the road and traffic ahead of
the motor vehicle.
(2) Instead of complying with the requirement of paragraph (1) a vehicle may comply with
Community Directive 77/649, 81/643, 88/366, 90/630 or, in the case of an agricultural
motor vehicle, 79/1073.
(3) All glass or other transparent material fitted to a motor vehicle shall be maintained in
such condition that it does not obscure the vision of the driver while the vehicle is being
driven on a road.
As long as there is nothing in front of the B pillar there is no problem, think of vans.