A new route, consisting partly of an entirely new dual two-lane road and partly an upgrade to the existing A548, between the A55 at junction 33 (the A5119 at Northop) and the A494/A550 junction complex at Shotwick, intended to relieve the existing A494 and A55 between those points. The new dual carriageway will run from the A55 at junction 33 to Connah's Quay Power Station. From that point, the A548 will be upgraded to form a free-flowing expressway with grade-separated junctions, crossing the Flintshire Bridge, with a new direct connection to the A494 at Shotwick leading to the M56.
At the connection points with the A55, A548 and A494, the new route will form the mainline through the junction, so that the effect when completed will be that the direct, main route from the end of the M56 will be a dual two-lane road that flows seamlessly across the Flintshire Bridge and on to the A55 at Northop. The finished route is intended to form the new main road between north-west England and north Wales, and it is possible that it will take the number A55 to emphasise its status.
The eastern end of the scheme, where the upgraded route will connect to the A494, is in England, and it is not yet clear how that part will be financed or built, though it is unlikely that Highways England would be obstructive. The likelihood is that the Welsh Assembly will pay for the work on the English side of the border as part of their scheme and that it will be carried out by the same contractor subject to approval of the designs and the finished work by Highways England.
Unlike many widening and upgrade schemes, this project does not arise from a need to improve capacity on the A548 Deeside corridor itself, but is actually being done as a way of alleviating congestion on the parallel A494 route across the Queensferry Bridge. It is the successor to an earlier scheme, A494 Queensferry-Ewloe, promoted by the Welsh Assembly in the 2000s that proposed widening the A494 to dual four-lane standard. Between Shotwick and Queensferry the A494 was upgraded to that width and an unused section of the southbound carriageway exists just north of the Queensferry Bridge that was built in anticipation of the widening continuing towards Ewloe. That scheme faced great opposition at its public inquiry and was dropped in 2008 when the Assembly decided that the scheme was too big and too costly. This is, therefore, an attempt to achieve the same result in a less expensive and controversial way - and if it does come in at the current estimated cost of £250m it will be very good value for money indeed.