The upgrading of the A5117 on a section west of the M56 motorway, Dunkirk roundabout to Sealand was started in 2006. It is regularly congested but the improvement will see the road converted to grade separated 2-lane dual carriageway standard . The Government decided that a motorway standard M56 extension would be too environmentally damaging, and instead opted for a route utilising part of the existing road without widening works, whilst providing off-line bypasses for all of the at-grade junctions. The improvements will tie in to recently completed works over the Welsh border which upgraded the A550 to a standard similar to that of motorways. Work started in late 2006 for completion by mid 2008.
The road was built in the 1930s and known as the "Shotwick - Helsby Bypass". It formed a link between Manchester, the North West and North Wales via the Queensferry Lifting bridge, the A550 and the A494, to join the A55 at Ewloe. Some sections were constructed in concrete. The road was lined for much of its length with poplar trees. This original tree lined boulevard layout is still in evidence on the section adjacent to Stanlow Refinery. In the 1960s it was marked out as a single carriageway 3-lane road. The middle lane was known as the "suicide" lane due to overtaking vehicles from each direction heading towards each other at speed. Vehicles in the nearside lanes would experience an up and down vertical motion due to the need for "summit and valley" drainage on this otherwise flat section of road.