Dublin's traffic authorities expect a crash to close Dublin Port Tunnel once every two weeks, while training exercises will close the tunnel at least once every two months.
The expected accident risks were disclosed at a meeting on November 24th in the National Roads Authority (NRA) headquarters, attended by representatives of the NRA, Dublin City Council, the Dublin Port Company and the Port Tunnel Operating Company. The meeting was told the collision rate - involving anything from a tyre blow out to crashes between vehicles or vehicles and the tunnel structure - could lead to the closure of the tunnel to traffic.
This risk was separate to the risk of closure from congestion at the northern portal where traffic from the M1 mixes with tunnel traffic in a "weaving" movement.
It was also separate to the risk of a roll-on, roll-off ferry arriving late by one hour or more into Dublin Port in the early hours of the morning - as happened as recently as yesterday morning.
The traffic authorities have also worked out that when Dublin City Council's heavy goods vehicle ban is in place in February, a port tunnel closure at peak time would result in 700 lorries sitting in the port area.
The meeting heard that a decision to relax the city centre ban could be made in just 15 minutes but would take another 45 minutes to be implemented and be notified to the gardaí.
The one hour delay could result in the 700 lorries vacating the port by 7.15am instead of the usual 6.15am. It can take the lorries 90 minutes to cross the city.
It has also emerged separately that when the tunnel needs to be immediately cleared of traffic, northbound vehicles on the M1 will be stopped by a newly installed set of traffic lights.
On the general risk of accidents the Fine Gael TD Olivia Mitchell has established that when works on the third lane started on the M50 last August more then 100 minor incidents were reported which resulted in severe congestion on the roadway.
Ms Mitchell said the traffic arrangements were a cause of great concern, particularly in relation to the risk of congestion on the M50 and she called on the minister Mr Cullen to "buy time" at the West-Link bridge allowing it to be raised to traffic at peak times.
As details of traffic management plans in the area start to emerge, expressions of concern have been made by a number of bodies including the Irish Road Haulage Association, while the latest body was Dublin Port itself.
Chief executive of the port company, Enda Connellan, told an Oireachtas Committee last week that while the tunnel was very welcome, the company had serious worries.
Mr Connellan told the committee that no fewer than four separate traffic authorities would be responsible for vehicles approaching the tunnel. These were Dublin City Council which has responsibility for the M50; Fingal County Council which has responsibility for traffic coming from the north Dublin area; the private company operating the tunnel; and Dublin Port itself, through which the lorries arrive and depart.
"We would favour responsibility for managing traffic flows to and from the tunnel being vested in the tunnel management company and not four disparate authorities," said Mr Connellan.
He added that he found it "incomprehensible that the construction work on new capacity on the M50 does not proceed through the night" and believed that the third lane of the M50 should have been put in place in advance of the Port Tunnel opening.
