Cork pedestrians will be given their first, and probably last, chance to walk under their beloved Lee next month and to do their bit for a good cause at the same time.
A charity walk organised by Glanmire and Douglas Rotary Clubs is planned to take place through the new Lee tunnel on the weekend after its eagerly-awaited opening on May 21st.
After that it will be motorised vehicles only, up to 30,000 of them a day at an average speed of 40 m.p.h., and the new facility will become so vital to Cork's traffic management that it is unlikely to be made available again for pedestrian events.
After two public inquiries, a major environmental impact study and more than four years of construction work, the tunnel project, the first under-river crossing in the country, is nearing completion.
With its associated 4.2 km of new dual carriageway, it will provide a complete by-pass of Cork on the southern perimeter of the city.
It has been a major engineering feat, the biggest infrastructural project undertaken by a local authority, and its operation will involve the most sophisticated mechanical, electrical and computer control systems.
Officially named the Jack Lynch Tunnel, it is 610 metres long with twin bores, each allowing two lanes of unidirectional traffic. The northbound and southbound traffic will thus be completely separated, a major safety factor.
With the heavy civil engineering and concrete works completed, the emphasis is now on testing and commissioning the control systems which will manage aspects such as ventilation, lighting, traffic control and emergency measures.
The total environment within the tunnel will be controlled by these systems. The concentration of carbon monoxide will be continuously monitored, although under normal operation the piston effect of the traffic itself will provide ventilation. Extra ventilation should only become necessary in the event of traffic stopping within the tunnel.
Eighteen cameras will monitor traffic and measure its speed, immediately sensing any stopped vehicle or one travelling in the wrong direction (such things have been known to happen even on the best regulated one-way streets!).
A separately ventilated central maintenance passageway will be available to tunnel users in the event of a traffic incident, and this safe refuge and escape route can be accessed through emergency doors every 100 metres along each traffic bore. Emergency telephones are located every 50 metres.
A speed limit of 50 m.p.h. will apply, and if traffic speed, as expected, averages 40 m.p.h., the travel time through the tunnel will average 35-40 seconds. No pedestrians, cyclists, horse-drawn vehicles or animals on foot will be allowed to use it in normal operation.
Cork Corporation's liaison engineer on the project, Mr Finbarr Long, points out that, statistically, accident rates in relatively short tunnels such as this are lower per million vehicle miles than on normal roadways.
Usage of the tunnel could gradually increase to about 40,000 vehicles per day over the next 20 years, and it is hoped that this will include most of the heavy goods vehicle traffic which formerly percolated though the city.
Journey times for vehicles crossing the city should be reduced by 10 to 15 minutes, depending on the time of travel, and the city-centre should benefit as the reduced traffic intrusion permits environmental improvements and pedestrianisation to be undertaken.
The entire scheme, costing about £105 million overall, is being financed by the National Roads Authority and is 85 per cent grant-aided from the EU Cohesion Fund. The tunnel contract itself, with its immediate 1.8km of approach roads, cost £75 million.
The tunnel will provide easier access from the north side of the Lee to major facilities on the west and south of Cork city, such as the airport, the regional hospital, educational institutes and the lower harbour industrial area.
Through traffic heading for the towns and villages of west Cork and south Kerry will also have the choice of avoiding the congested city-centre.
This radical project should at last substantially relieve Cork's notorious traffic congestion. That, at least, was the theory advanced by the Cork Land Use and Transportation Study in 1978 which put forward the proposal for a downstream crossing of the Lee.
After May 21st, and the once-off under-river charity walk, Cork's commuters and visitors alike will be able to judge for themselves the impact of this enormous new infrastructural feature.