The boxes have been painted next to 14 central cashpoints

Avon and Somerset Police, which is behind the initiative, says the boxes will help fight crime at the machines.

The aim is to thwart tactics like "shoulder surfing" whereby would-be robbers try to spot users' PIN numbers.

After a successful pilot scheme in Broadmead, the boxes have been brought in at 14 other banks and building societies in the city centre.

It is hoped the yellow areas will encourage queuing people to stand outside the box, allowing privacy for the person using the machine.

If someone steps into the "safe" space, police say the card user can legitimately ask why the person has done that.

John Hirst, the manager of Broadmead, where the pilot took place, said: "Creating a defensible space in front of cash machines seems to reduce the number of robberies associated with these machines.

"Research has revealed that they have many benefits, not least increasing the awareness of the user, which in turn makes it more difficult for a criminal to maintain close proximity to potential victims."