Switch Island

The first roundabout layout, linking the A59 road to what was then the A567 road

The junction originates from the construction of Dunnings Bridge Road during the 1930s,[3] linking what is now known as the A59 to the A5036 (then known as the A567 road).[4][5] A simple roundabout was constructed sometime during the 1930s - 1940s[6] and remained in this unchanged configuration until construction of the M57 motorway reached the island in 1974.

The original island remained virtually unchanged for almost 40 years, until the new motorway joined the road and the original island fell out of use as the layout around it changed to accommodate roads for the motorway junction. A road map from 1975 shows the original island alongside new roads to the east connecting the motorway, despite suggesting it was not functional in its original roundabout configuration.[7]

Switch Island with the then-new M57 connected

During phase 2 of the M57 construction in the mid 1970s, the motorway was routed to terminate at the junction, which involved constructing a new link road for the entry and exit sliproads, with the original roundabout becoming largely redundant. The new road connecting the M57 motorway would later become the eastern section of the future island roundabout.

The previous two-way traffic road changed to a northbound route only, with southbound traffic now using the new motorway link road, connecting up to the A59 road at what was the former roundabout.

Switch Island after M58 motorway construction

Subsequent to the M58 motorway being constructed and also linked to the junction, the western half of the island was constructed thus completing a roundabout island that was entirely separate to what had been originally constructed prior to the motorways. The plans for the two motorways involved them converging at this junction then continuing west, whilst the A59 continued uninterrupted under (or over) the island in a grade separation arrangement, with slip roads to and from the junction. These plans never saw fruition and instead all roads converge at a single flat level intersection junction.

Aside from various improvement works over the years, the configuration of the island from 1980 onwards has changed little, with the exception of considerably more traffic utilising the junction and additional roads being constructed within and to the junction.

The junction underwent a minor redesign in 2006 when new section of carriageway was built at the M57 terminus, allowing motorists to directly transfer onto either the A5036 or A59 roads.[8] The primary objective was to ensure the junction could withstand the predicted increase in road traffic for the next decade and help improve the flow of an estimated 43,000 vehicles daily.[8] At this time, the island was handling up to 80,000 vehicles every day, of which 10% were heavy goods vehicles and resulting in extensive traffic queues leading to increased risks of traffic accidents.[9] The roadworks completed in Spring 2006, resulting in a revised junction layout and removing the roundabout configuration. A short stretch of the original roundabout remained in existence to be utilised as an inspection area and weighbridge, operated by the Vehicle Inspectorate; this was reconstructed following construction of the new Thornton to Switch island link road which has carriageway in some parts of the old roundabout.

In September 2013, Sefton Council approved construction of the long-campaigned[10] Thornton to Switch island link road, which started construction towards the end of the 2013 calendar year[11] and opened on 19 August 2015 as the A5758 Broom's Cross Road. The route connects to the junction at its western side and provides a more efficient route from the A565 road. Further improvements were announced in April 2017 for work to take place during 2018, including new traffic light installations, changes to lane markings, new barriers between carriageways and improved signage.[12]

In May 2018 these roadworks were named as the most dangerous in England.[13]