a bridge design for the Clifton Suspension Bridge that visually reflects the amount of cars travelling into & out of the city each day, as a sort of huge-scale "Environmental Strain Gauge".
everyone in the community can take part & contribute to make the bridge a cool blue. various points around the City of Bristol measure the number of cars passing by, which then affects the lights on the bridge. many people using cars turns the bridge ugly red, while car sharing results in blue, as it helps ease congestion & pollution.
see also inside out & alien landing strip & litmus.