There have been changeable message signs for longer than you might think. While automated, remote control and electronic signs might have been developments from the 1960s and 70s, other more basic types of changeable sign had been around for much longer.
The creation of parking controls to reduce city centre congestion created a need for a particularly odd changeable sign, which was deployed on streets where parking would only be allowed on one side. Frequently, traders on opposite sides of the street wanted parking to be allowed on their half of the street, claiming that banning parking in front of their shops would harm trade.
In the yard at the foot of the Metropolitan Line embankment, Bergo's engineers demonstrated their breakthrough: a lens 40 centimetres (16 inches) across that was completely black, even in direct sunlight, but which could then be illuminated. They put several masks over the light to show a red cross, as in a lane indicator; the word ICE; and the outline of a letter E, to demonstrate the concept.
With — at last — some working technology, there was now the possibility to begin trying out new ideas to keep the traffic flowing.
Picture credits
- Changeable "no waiting" and "waiting limited" sign taken from fingerpostsigns.com
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Photograph of Tamar Bridge adapted from an original by Stuart Logan and used under this Creative Commons licence.
