The security barriers causing traffic chaos at Waverley Station have been going into lockdown when cabbies unwittingly move too quickly to get through them.
Concerns were raised after new automatic barriers were installed without adequate warning, with city transport leader Lesley Hinds raising fears the resulting traffic could put pedestrians at risk.
Now it has emerged that huge tailbacks along Waverley Bridge in recent days were caused by taxi drivers jumping a red light in a bid to speed up the slow-moving entry system – a move which in fact shut it down in an automatic response to what the computers believed was an illegal entry.
An engineering source said: “When the barrier went down at the second gate, taxis were pulling off but the light was still red. This fooled the computer into thinking that a vehicle without security clearance had entered.
“The whole system would then have to be shut down while an engineer went out to reset it. The sequencing between the barrier going down and the light going green has now been shortened.”
The barriers were turned off less than 24 hours after being installed on Monday after the delays resulted in queues of cabbies stretching out on to Waverley Bridge and almost as far back as Princes Street.
Under the new arrangements taxis must pay £1800 a year for a permit to enter the station.
Central Taxis director Tony Kenmuir said: “Surely they should have given cabbies some training or indication on how to work it instead of expecting everyone to pick it up in an instant?”
When the plans were first announced as part of UK Home Office terror policy last year, the city council said it was “crucial” to install a new zebra crossing at the junction of Market Street and Waverley Bridge, and work to install these improvements is now set to begin by Easter.
A 12-bay taxi rank on Market Street and footway widening on Waverley Bridge are also set to be developed.
Cllr Hinds said: “The plan was that this would all happen at around the same time the barriers went in. However, the first I knew of the barriers was upon being contacted by the press, and that was also the first the officers planning the improvements heard of it too.”
However this was refuted by Network Rail, which claims to have postponed restricting vehicle access several times over the past two years while awaiting council developments.
A spokesman said: “We have invested over £130m in Waverley over the last four years renewing the roof, refurbishing the concourse and upgrading the entrances and the station is now more accessible than at any time in its history.
“We have been in discussions over this issue for more than five years and have delayed the introduction of restrictions for the past two years, but we could not continue to postpone their introduction indefinitely.”