Routemaster
The Routemaster is the fast disappearing traditional London bus distinguished by the open footplate at the back from which eager young people have traditionally hung to symbolise carefree youth in any movie featuring Swinging London.
See: Cliff Richard in Summer Holiday (if you dare).
Offers the same cheap cinematic shorthand as...
Scooter :- Rome
Yellow Taxi :- New York City
Idiotic stretch limo :- Los Angeles
Datsun with failing brakes, no door linings and fake insurance :- Anywhere South of the Thames