Full reopening of the Forth Road Bridge has been delayed by up to month with only 600 HGVs permitted to travel north during the early hours from tonight.
Engineers have discovered a problem on the south tower – on the other side of the bridge from the north tower, where a crack was found in December.
They have stressed that the problem, related to the movement of truss end links, will not cause another breakage but say work is required to strengthen it.
Ministers had hoped to reopen fully in mid-February but storms and the additional problem has slowed their progress, with full reopening now expected in mid-March.
Transport Minister Derek Mackay has called for understanding from the haulage industry, who he said are “understandably tense” about the delay.
He said he cannot quantify how much the delay will cost the industry or the Scottish economy. But he urged the Road Haulage Association (RHA) to look again at their figures which suggested the closure was costing firms £600,000 a day.
Phased reintroduction of HGVs is due to begin from tonight.
Photos from last night showing construction of bracket at NE tower for phase 2 truss end link works: pic.twitter.com/AASBR6iFIU
— Forth Road Bridge (@forthroadbridge) February 4, 2016
Up to 600 northbound HGVs will be allowed on the northbound carriageway between 11pm and 4am every night – subject to weather conditions.
The next phase of repair work is even more weather-dependent than the original repair as work is done above the carriageway on mobile platforms which are more susceptible to wind.
A dedicated HGV lane and stacking area will be in operation to help manage the traffic flow across the bridge.
Traffic signals will release HGVs on to the bridge at a rate of one every 30 seconds.
https://youtube.com/watch?v=6g4FlniVOFk%3Frel%3D0
Mr Mackay said: “Of course there will be a degree of disappointment that there is not unrestricted access, but (the haulage industry) appreciate that we are doing everything we can to ensure safety, and to not cause any further damage to the bridge so that it can open satisfactorily as soon as possible within that timescale of mid-March.
“Some people said HGVs would never cross the Forth Road Bridge again. Well, they will as of this evening and that trial will inform further works.There will be ongoing dialogue with the industry to talk about the impact and other measures that we can deliver to support them.
“I have engaged with them. They appreciate all the efforts that are going in to fully repair the bridge and ensure that it opens as quickly as possible.
“I know that they are understandably tense about the impact on the industry and they want a degree of certainty about the opening.”
The Road Haulage Association (RHA) said previously that the closure is costing firms £600,000 a day.
Mr Mackay said: “I think they would probably want to themselves look again at their figures and methodology, but again I am happy to engage as that. I as Transport Minister am very focused on the structure of the bridge and getting traffic across.”
Mark Arndt, chartered engineer and Amey’s account director for the Forth Road Bridge, said: “The HGV stack that we have in place can accommodate 20 vehicles, which means we can get 600 HGVs on to the bridge per night.
“Pre-December there were about 450 vehicles using the bridge during that window, so it is approximately a 50% increase in terms of the allowance on that window.
“But it certainly doesn’t accommodate the 7,000 HGVs that normally use the bridge.It’s important that the HGV industry realise that, but we are working as best as we can to get it fully open.”
HGVs have been banned from the bridge since December 3, two days before it was then shut to all traffic.
Lighter vehicles were allowed back on to the bridge on December 23.