west across western metropolitan Sydney to Penrith, north of the central business district, crossing the Nepean River via the 1867 Victoria Bridge. Cumberland Highway links the Pacific Highway (A1/B83) and Pacific Motorway (M1) at Pearces Corner, Wahroonga in the northeast with the Hume Highway (A22/A28) at Liverpool in the southwest. The M5 Motorway is the primary route from to the Sydney CBD, with its terminus being in the south of an interchange near Prestons where the M5 meets the Westlink M7 and the M31 Hume Motorway. The A6 is a major arterial road that provides a link from the northern and western suburbs to the centre western suburbs – Bankstown and the Princes Highway at , via Lidcombe and Bankstown. Henry Lawson Drive was conceived of as a scenic drive to follow the north bank of the Georges River in Sydney's southwest. The Light Horse Interchange is a motorway interchange located in Eastern Creek at the junction of the M4 Western Motorway and the Westlink M7 that was opened to traffic in December 2005 due to the population boom in Sydney's western suburbs. Politics Greater Western Sydney local government authorities agree on the broad definition of greater western Sydney, but divide the region based on the regional organisations of councils. The Western Sydney Regional Organisation of Councils (WSROC) includes the local government areas of Blacktown, Canterbury-Bankstown, Fairfield, Hawkesbury, Cumberland, Liverpool, Parramatta and Penrith. The Macarthur Regional Organisation of Councils (MACROC) includes the local government areas of Camden, Campbelltown and Wollondilly. In government administration, the region has a Minister for Western Sydney, currently held by the Hon. David Elliott, MP. Western Sydney is home to a large number of marginal electorates at both a state and federal level. Western Sydney includes, or partially includes, the NSW Electoral Districts of Penrith, Londonderry, Mulgoa, Camden, Macquarie Fields, Campbelltown, Liverpool, Cabramatta, Fairfield, Prospect, Bankstown, Granville, Parramatta, Seven Hills, Baulkham Hills, Castle Hill, Riverstone, Mount Druitt, Blacktown, Holsworthy, Bankstown, Auburn, Hawkesbury. Western Sydney is considered a particularly crucial region in federal politics, and the region's social conservativism has been credited with forming policy on migration and the treatment of asylum seekers by both major political parties. Western Sydney voted 'no' in high margins in the Australian Marriage Law Postal Survey held in 2017. 12 of the 17 divisions that voted 'no' nationally were from Western Sydney. Despite this, Western Sydney is largely dominated by Labor,