Guy King wrote:
The message
from Tony Polson contains these words:

You cannot make them cross. They just do it themselves. There is no
input from the user, other than to hold the rods so that they can
respond to whatever it is that makes them cross.

So why aren't automated dowsing trolleys seen roaming the streets
looking for all the lost services the utility firms keep digging up the
roads in search of?

Too easy...