Edwina Hart, Minister for Economy, Science and Transport
Britannia Bridge is monitored 24 hours a day by operators at the North Wales Traffic Management Centre, Conwy. A number of means are used to monitor and operate the bridge and its approaches. In the case of adverse weather these means include CCTV, Variable Message Signs and anemometers.
On 25 January the anemometer system went into fault and readings were lost, the suspected cause a lightning strike at the bridge. On 29/30 January a temporary anemometer system was installed at the transmission building immediately to the south of the bridge. As this system was taking readings at a more sheltered location, a safety factor of 2.2 was applied to the readings before using them to inform decisions on the operation of the bridge.
On 12 February, with very strong winds forecast, Silver Command was set up, operators were put on heightened alert and, because the temporary anemometer system was still in use, engineers were deployed to both ends of Britannia bridge to take hand held wind speed measurements every 30 minutes and Welsh Government Traffic Officers were deployed to patrol the bridge. It was also agreed that additional information from forecasts and from the wind measurement system at the Port of Holyhead would be taken into account during the decision making process. The findings from all those sources were used by the Silver Manager to inform his decisions, in liaison with North Wales Police.
In managing the bridge during high winds there are a number of trigger levels that instigate responses by operators. Those trigger levels demand the following operational responses:
- Level 1: High wind warnings and advisory 30mph speed limit;
- Level 2: High wind warnings, advisory 20 mph speed limit and bridge closed to high sided vehicles;
- Level 3: Bridge closed to all vehicles;
- Level 4: Bridge closed to all vehicles, structural survey required before bridge can be re-open.
On 12 February the bridge had been operating at Level 2 (closed to high sided vehicles) for nearly 2 hours before a Large Goods Vehicle (LGV) overturned on the bridge at 1546 hours, the driver having driven through the signed closure; he was subsequently found guilty of careless driving. A crane was brought in to right the overturned vehicle but the bridge was closed for a longer period than would have been normal as the crane could not operate until the winds fell below 20mph. Thus recovery of the vehicle and re-opening of the bridge was not complete until 0840 on 13th February.
Throughout the closure period LGVs were ‘stacked’ on the mainland at Bryn Cegin, Llandygai and on the Felinheli bypass. On the island most LGVs remained at Holyhead Port. All light vehicles were diverted over the Menai bridge.
As with all such significant incidents, a multi-agency de-brief will take place and any lessons learned will be incorporated into the Britannia bridge operation and maintenance procedures.