Jack Lynch Tunnel operators warn motorists to expect more over-height vehicle alerts

An over-height vehicle alert at peak rush-hour on Monday morning caused traffic gridlock but more could be on the way due to a new detection system

The new vehicle height detection system installed in the Jack Lynch Tunnel. Photo: Transport Infrastructure Ireland

Motorists who use the Jack Lynch Tunnel in Cork have been warned to expect more over-height vehicle alerts and delays following the installation of a new, more sensitive detection system.

The warning follows another over-height vehicle alert at peak rush-hour on Monday morning — the latest in a series of such alerts at the critical piece of road infrastructure on the eastern outskirts of the city which handles up to 70,000 vehicles a day. The incidents have led to traffic gridlock and fuelled driver anger.

Transport Infrastructure Ireland (TII), which is responsible for the management and maintenance of the tunnel, confirmed the new system has triggered several “false detections” since it was installed in March, including one last week, and another the previous week.

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That false detection triggered a response from Cork City fire brigade, which had to stand down a unit en route to the scene when it became clear it was a false alarm.

However, the spokesman confirmed Monday’s alert was a “valid detection” of an oversized vehicle or load approaching the tunnel, which has a regulated height restriction of 4.6m, or just over 15ft.

The incident at the southbound bore at 8.20am forced a bore closure for some time while the offending vehicle was rerouted. It caused massive tailbacks and knock-on delays for commuters.

He said the initial kinks in the system have been ironed out and both TII and the company which manages and monitors the tunnel and its systems on its behalf are now satisfied the new sensors have been fully calibrated and the entire system is operating correctly.

It is understood testing of the system is ongoing.

The spokesman said a decision was taken in recent months to upgrade the vehicle height detection system in parallel with the massive Dunkettle Interchange project.

The old system and sensors were removed and a new modern sophisticated system, with much more sensitive and accurate vehicle height detecting sensors, was installed in March.

The sensors, installed in an array on the approaches to the tunnel’s north and southbound bores, are designed to detect vehicles or loads above the regulated permitted height of 4.6m.

Vehicles or loads above that height pose a strike risk to the tunnel’s internal infrastructure, including its warning signs, its fire suppression systems, and its massive exhaust extractor fans.

If an over-height vehicle is detected, the system triggers a series of warning signs, including a large variable messaging sign over the tunnel entrances advising motorists that the tunnel is closed, traffic lights at the bore entrance flash red, and red LED road studs also flash red.

Motorists have to stop until the system is reset and the offending vehicle is removed. The TII spokesman said now the new more accurate system is operating correctly, it will detect more over-height vehicles.

They added that motorists, especially hauliers, should be aware of the increased sensitivity of the sensors in a tunnel with a 4.6m height restriction. Special ‘abnormal load’ permits can be obtained from TII to facilitate the transport of oversized loads through the tunnel.

This usually involves a complex traffic management operation, with input from gardaí and the local authority.