Steve, very good point...
EI-RB, here's one to stir things up, under current Road Traffic Legislation (I can dig up the Act & Section if needs be) HGV's are prohibited from using the carraigeway adjacent to the central margin on Motorways, largely ignored as you may have guessed. The entrance to the Port Tunnel from the M1 will involve HGV traffic moving to these prohibitied outside lanes - leading into the tunnel and all other surface city traffic, ie faster moving cars, taxis etc moving to the inside lanes. Apart from the chaos, imagine the court case following the inevitible collision...
