But police sources questioned whether the plan could work properly without more effective powers to stop and search vehicles.
The experiment, which has been approved by the City of London Corporation, will involve blocking off minor roads and putting police checkpoints on main routes into the City.
It is designed to provide reassurance for City institutions in the wake of the Bishopsgate and Baltic Exchange bombings. The corporation said the measures would be 'unobtrusive' and would not replicate 'Belfast-style checkpoints'. The police are empowered to close off minor roads in the City under the Road Traffic Regulation Act 1984 for six months. This is renewable for a further six months, but beyond that new legislation would be required. Police powers to stop and search vehicles at checkpoints are enshrined in the Police and Criminal Evidence Act 1984. But, in effect, searches can only be carried out with drivers' permission unless there are reasonable grounds for suspecting stolen or prohibited articles will be found.
This has led senior City officers to question how effective the checkpoints will be unless police can carry out random searches. Any attempt to tighten the law in this area is likely to meet with opposition from civil liberties groups concerned about the individual's right to privacy.
There is some support in the City for more extreme measures which would involve setting up permanent barriers at entry points and allowing in only buses, taxis and vehicles with special licences. This would require a public inquiry and new legislation.