A direct communication winner for Greentomatocars!

A real eco-brand has won a Bronze Lion at the Advertising Festival in Cannes: Greentomatocars in London has promoted its services in a direct and very surprizing way:

Brief:
Greentomatocars is a taxi service which uses the greenest car around - the Toyota Prius. Moreover they plant thousands of trees a year to make up for unavoidable emissions whilst getting people from A to B. To generate customers they needed to advertise locally. For taxi firms this usually means doing a doordrop. But how do you do a doordrop that isn't wasteful of paper? And, in this case, a contradiction of the whole idea of the Green Taxi service?
Solution:
Produce a single doordrop that can be passed around the neighbourhood. Each street gets just one doordrop each. The first recipient ticks off their address once they've noted the taxi number and then passes it on to the next neighbour. And so on, until the whole street has seen this one doordrop.
Result:
We targeted households within a two mile radius of the West London office of Greentomatocars. Month on month bookings increased 11%. The rise can only be attributable to the doordrop. The client is now extending the doordrop activity into South West London (and, thereafter, North West London).