Colourful pavements

I suspect many people know the different colours are different kinds of utility: red for power, orange for telecoms, blue is water, yellow for gas, etc.

How do they know where to draw the lines? Some of it is data, some of it is probing. According to “Underground Utility Colour Codes Explained”:

For metal pipes and similar cables, electromagnetic equipment with a transmitter and receiver is used. For plastics and concrete, radio location and ground penetrating radars are used.

Utilities such as petroleum products are permanently marked using posts and bollards due to the nature of their content. There are maps to locate these utilities but certain equipment is required in order to have a precise and accurate location.

Links:

• The BBC has example marks decoded (April 2014).
• Street Works (formally National Joint Utilities Group) publishes guidelines.