What's wrong with the Aberdeen bypass?

Published on 01 February 2019

The A90 Aberdeen Western Peripheral Route (AWPR) is by far the biggest road construction project the UK has seen for years: 36 miles of dual carriageway built as a single scheme. It was due to open last spring - but there's something very wrong with the bridge over the River Don.

Project sign for the AWPR works. Click to enlarge
Project sign for the AWPR works. Click to enlarge

What exactly is wrong with the bridge over the Don is the cause of much discussion at the moment, and it's been suggested to us that the problems are actually much worse, and potentially have graver consequences, than has so far been made apparent. But more on that shortly. First, we should take stock of just how long it's taken to get to this sorry situation.

The River Don is far from the only problem the AWPR has suffered. It's fair to say this has been a troubled project. If you haven't been following the blow-by-blow updates on our Road Schemes page since it first appeared in early 2003 (yes, that's 16 years we've been watching this project), and if you're not local to Aberdeen, you might have missed some of the drama.

Approval was given for the bypass in 2004, but delayed initially because of protests about the route passing through the grounds of a special needs school. Rather improbably that campaign was led by Timmy Mallett. An alternative route was selected in 2005, and that proposal went to a much-delayed public inquiry, holding up the start date by a full three years. Ministerial approval came in December 2009, and a completion date of 2012 was announced, which, if nothing else, tells us the ministers concerned were committed optimists. The estimated cost was £395m.

In early 2010, a local campaign group called Road Sense launched their first legal challenge: they would continue to challenge and appeal each ruling, eventually leading to a hearing at the Supreme Court in London in 2012. Preparatory work continued in the background, but even the end of the Supreme Court hearing couldn't hurry the AWPR along. Work eventually started on site in late 2014, with First Minister Nicola Sturgeon formally inaugurating the works in February 2015. The opening date of late 2017 was pushed back to spring 2018, and the price tag grew to £745m.

Delays, delays, delays

Spring 2018 came and went, and the AWPR did not open. Problems with utilities crossing the line of the road, a spate of particularly bad winter weather and the collapse of the construction company Carillion all contributed to a major overrun. Indeed, cost overruns on the AWPR were allegedly one of the reasons Carillion went under. Not to worry, though: it would be open by the autumn.

When autumn came and went, the promise became the end of the year.

In early December it was apparent to everybody that defects found at the Don crossing were holding up the opening of an otherwise finished road - but the nature of the contract meant that, legally, it all had to open at the same time. The Scottish Government, desperate to get traffic on to some part of the new road in at least the same year as its promised opening date, sent the lawyers in and negotiated a variation to the contract. On 12 December 2018, most of it did indeed open to traffic, but not the Don bridge.

Giving evidence to the Scottish Government’s Rural Economy and Connectivity committee on 4 December, Stephen Tarr, Balfour Beatty's Major Projects Managing Director said they hoped to open the bridge later that month. But on 21 December the message changed - the bridge would now not be ready until the end of January.

The AWPR Don crossing, as it appeared on 23 December. Click to enlarge
The AWPR Don crossing, as it appeared on 23 December. Click to enlarge

The end of January was yesterday, and the bridge isn't open. The Scottish Transport Minister, Michael Matheson, told the Evening Express:

"I am pleased to report all remaining physical works at the Don Crossing have finished. But the road can only be fully opened once ministers receive the necessary assurances about the longer term impact of the remedial work and the changed costs of future maintenance.

"To put it more simply, we are not prepared to pick up the tab for mistakes made by construction companies."

In other words, the bridge is done, but can't be opened until someone agrees to pay to maintain it long term. Why is that even a question? What does the "longer term impact of the remedial work" mean? Why have the costs of future maintenance of the bridge "changed"?

Parkhill junction, just east of the Don crossing, with the road beyond now open to traffic. Click to enlarge
Parkhill junction, just east of the Don crossing, with the road beyond now open to traffic. Click to enlarge

A troubled bridge over waters

The Don crossing is a bridge carrying the AWPR over the River Don just north of Aberdeen airport. It's a 300m long post-tensioned concrete structure - not uncommon, but fairly tricky to build. The vertical piers are built first, and then the beams spanning them are cantilevered out from the top of the piers towards each other, with the concrete being poured and formed in situ, in mid air, until section by section the gap is closed and the bridge is complete. The bridge over the Don required more than 70 individual sections to be cast in this way, each a box 3m square, and then brought under tension once complete.

In May 2018, as stress was applied to the bridge, cracks began to form on the underside, and work was halted while the defect was investigated. Stephen Tarr told the Scottish Government committee that these investigations took about two months, in which time the bridge was de-stressed again. The cause was the utility ducts passing through the structure, which didn't line up with those in the supporting piers, and the misalignment caused pressure around the ducts which in turn led to the cracks forming. To fix it, parts of the bridge deck were broken out and re-cast from scratch. This, Tarr said, had been finished by early December last year.

Reports on 23 January said that only "safety checks" needed to be finished before the bridge could open. The discussion has now moved on to money, with that odd question about "longer term remedial work" and the implication that maintaining the bridge will, in future, be more costly than it ought to be.

One suggestion that has reached us, and which might explain why the bridge will need close attention on an ongoing basis, is that not just the utility ducts but also the concrete reinforcement in the piers of the Don crossing were not built to specification. It's not clear whether the piers were rebuilt; certainly the only clear description of the remedial work suggests that sections of the deck were re-cast. There is now a concern among the civil engineers dealing with the bridge that the deck may not be able to carry its intended weight loading, and even - we are told - questions being asked about whether, long term, the supports will hold up. If those concerns are valid, it's conceivable that the bridge might have to be rebuilt.

Shuttering apparatus on the Don bridge as the central section is re-cast, September 2018. A gap in the deck is just visible. Click to enlarge
Shuttering apparatus on the Don bridge as the central section is re-cast, September 2018. A gap in the deck is just visible. Click to enlarge

Time will tell. Sooner or later, the AWPR will open and traffic will flow over the Don crossing at last. And we should be very clear that it will be perfectly safe to use - there is no evidence of doubt that the bridge is sound. That isn't in question.

The strong implication, though, is this: while the bridge might be finished and fully functional, it can't be assumed it will last its intended lifespan without more attention, and a programme of additional inspections and engineering work to ensure its stability can already be foreseen. Whether it will need more serious strengthening work at some point in the future - or whether, even, it will need to be pulled down and rebuilt from scratch at some point - we don't know. But that work, if it's needed, will cost money. And certainly, something is still not right. On 23 January, a Transport Scotland spokesperson told the press that the contractors had "known for some time that technical assurances regarding the longer term impact of its complex repairs to the defects on the Don Crossing were required." If the repairs had resulted in a bridge that was now built and operating fully according to spec, it's hard to imagine those assurances would still be a point of contention two months after the thing was finished.

One thing is for sure. We haven't yet seen the end of the AWPR saga.

Elsewhere on


Anonymous 1 February 2019

A friend of a friend who used to work in Aberdeenshire Council (one of the scheme's sponsors) was told that "the wrong type of concrete" had been used during the construction. Only hearsay. However this would align with the current delay. No sign of the current diversions / cones / blacked out direction signs being altered.

Patrickov 3 February 2019

If not even London can get their schemes right (admittedly it's more about railways down there), it's not surprising that the AWPR is also on a crashing course.

NC 3 February 2019

I believe one of the bridges (this one I think), crosses a major (offshore?) oil/gas pipeline, perhaps further adding to concerns

andrinaf 4 February 2019

If you actually look up close at the quality of the workmanship underneath all of the bridges you will see that some serious corners have been cut. In at least 2 areas ie, 1 going towards blackdog the underpass is crumbling and huge chunks have fallen out due to "poor" workmanship and very cheap materials. This is going to be a massive white elephant in the long term.

Rossco 4 February 2019

Other than the Don Bridge, there are one or two other points worth mentioning. The junctions at either end really should have been free flowing, as should the Cleanhill roundabout.
The signage is particularly poorly designed in my opinion.
Quite regularly in the morning peak there are queues back up the slip road from the A944 roundabout onto the northbound carriageway.
Other than these gripes the road has served its purpose very well and the traffic through the city is noticeably quieter since the opening.

"Other than these gripes the road has served its purpose very well and the traffic through the city is noticeably quieter since the opening."

Coulda fooled me. City traffic is still pretty abysmal at all the usual locations & times, which makes sense since Aberdeen's major traffic concerns have always been getting in & out of the city, not around it.

There might be a few less heavy trucks on King Street, etc, and folk bypassing Aberdeen can certainly do so, so it serves a purpose, albeit very expensive.

KR 5 February 2019

I was sitting on the A93 North Deeside road,at the traffic lights on the bridge section heading into Culter from Aberdeen. A lorry full of earth/rubble came up the old B979 road and turned right, heading back into Aberdeen, As I sat there the whole bridge started to move as the lorry trundled past. It felt like the bridge was bouncing slightly, my car was rocking on it's springs. Other cars in front of me were doing the same, and the drivers were looking around. I know bridges have some form of movement (my dad is a structural engineer) but 4 cars and a fully laden dump truck shouldn't make the bridge flex like that.

My Mum was a Prison officer.
That doesn’t make me an expert in the criminal justice system.

I'm an Architect so have some insight in to how things are built, or should be built. I know nothing about prisons however.

KR 5 February 2019

The slip roads on and off are far too short.
Joining the AWPR northbound from the Deeside junction you have a very short slip road, which causes issues when drivers can't /don't move over to let you out.
The slip road joining the A90 from the A92 is approx 300m long, the slip road at the Deeside Junction northbound also joining the A90 is less than 90m before the lane narrows.
90m to join a stream of traffic at 70mph (31 meter / sec) so that's just under 3 seconds of slip road. Madness!

They are short, but don't appear any shorter than on other dual carriageway/expressway schemes built in the last ten or twenty years. There seems to be a preference for shorter merges now, and an expectation that drivers will match their speed with traffic on the main road as they approach, rather than having a long length of acceleration lane to match while alongside.

Concrete spec 6 February 2019

I can tell you this as I worked as part of a team on this project on both bridges the Dee and the Don, the concrete that is poured on both Bridges is the exact same mix designs and exceeded the requirements that were specified by the technical gurus, you will find it's just politics and financial reasons that it's not open, also due to Bp having the pipeline along side they are accountable for some of the delays in the building process of this bridge

Andy 6 February 2019

It will be a sad time when the final bridge is opened, nothing left to moan about.. sad times indeed for a lot of people.

John 6 February 2019

Having dealt with contractors for many years it seems to me that the old threatening tactics were being deployed here. Old school bullying doesn't work but working with and not against contractors DOES. If that had happened this would have been resolved long ago.
Far too much people want to blame rather than resolve !!!

Thomas 7 February 2019

I think the AWPR is a great piece of civil engineering...made a great difference to me travelling daily from Portlethen to Bridge of Don. ..even with the Don Bridge problems...here comes the but...I really think that average speed cameras need to be fitted as with the previous bad weather you still had people flying along well over the limit...no unmarked or visible police calming seen ...only safety cameras for a couple of weeks.
Why the need to speed when I'm already saving around 30 mins each way on my travelling time.
Slip roads are long enough when the limits are adhered to.
We really need more communication regarding the final piece.
Imagine getting full independence when they can't manage the awpr ,Edinburgh tramway and the new bridge in budget.

Jeezo! I you organised a barbie and it rained some people would blame SNP.
Let us examine your 'facts'.
Firstly, by your own admission the AWPR is a tremendous and time saving project. Long overdue! As the article states, the problems lie largely with the contractors.
Secondly, The SNP in a minority government voted to abandon the tram project but were outvoted by their fiscal superiors Lib/Lab/Tory. (Shhh! don't mention the 2 trillion UK debt). The project was managed by Edinburgh City Council.
Thirdly, the fantastic Queensferry Crossing came in UNDER budget!
But hey lets not let truth undermine your 'facts'!

Neil 9 February 2019

When the Don crossing is finally open it will save me time travelling to Ellon. However, in the meantime it's quicker to drive directly through Aberdeen as it takes up to 15 minutes to get around Dyce to get back on the AWPR the other side of the bridge.

Chris5156 14 February 2019

Further comments of a political nature won't be approved for publication here. This is not a forum for airing views for or against political parties.

Gerry McKenna 21 February 2019

Well I drove across the bridge yesterday and survived to write this update :). Survival suit had been packed but not required. Having driven the full length the road itself is fine however some of the junctions may need closer analysis for amendment. e.g. Kingswells South with peak traffic queuing to exit from both north and south. Maybe peak time lights. The Cleanhill roundabout has already had changes with the application of rumble strips to slow traffic - almost an accident a day so far. Overall a thumbs up.

Gareth Roberts 4 January 2020

I can't understand after the length of time it took to finally construct the Aberdeen by-pass and they still haven't allocated proper road signage. When you join the by-pass at Stonehaven traveling north there is not one single sign to indicate where the town of Ellon is untill you reach the roundabout on the outskirts of Ellon. This not the only poor display of adaquate road signage, along the entire route there is evidence of poor directions.
Does pose the question who and where the person came from who passed the amount and where the signs are situated.

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