South of Waterfall the highway is paralleled by the 55-kilometre (34 mi) Princes Motorway (national route M1) to the top of Bulli Pass outside the city of Wollongong, which carries the majority of traffic.

The Princes Highway then enters the northern suburbs of Wollongong and the Illawarra region via the Bulli Pass, whilst Mount Ousley Road, which is designated as part of national route 1, bypasses Wollongong's northern suburbs to meet the Princes Highway at Fairy Meadow, and carries inter-city traffic.

Duplication to dual carriageway standard of a 6-kilometre (4 mi) length south from here to Forest Road was scheduled for completion in early 2014, following a three-month cessation of work while measures were put in place to protect a hitherto unknown area of habitat of the endangered green and golden bell frog.

From Jervis Bay Road southward the highway is mostly single two lane carriageway along the NSW South Coast, passing through Ulladulla, Batemans Bay (where the 1-kilometre (0.6 mi) town centre bypass is built as dual carriageway), Moruya, Narooma, then bypassing Bega and Merimbula and passing through Eden, before crossing the border at the Black-Allen Line into Victoria, 550 kilometres (340 mi) from Sydney and 515 kilometres (320 mi) from Melbourne.

The route within metropolitan Melbourne carries the original individual names of sections of Princes Highway on signage.

The highway then passes through the Latrobe Valley, bypassing Morwell, Warragul and Pakenham to Dandenong and into the south-eastern suburbs of Melbourne.

The M1 include an advanced freeway management system for its entire 75-kilometre (47 mi) urban length, between Narre Warren and Werribee.

Along with freeway sensors and associated data stations, overhead lane use management system (LUMS) gantries that show speed and lane availability, electronic message boards, real-time drive time signs and arterial road real-time Information signs (before the on-ramps); there are the 64+ ramp signal and metering sites.

Which, unusually for an Australian inter-city freeway, carries enough traffic to merit four to three lanes in either direction (often still being congested in the morning and afternoon peaks).

After Geelong the highway heads in a generally western direction, continuing with the 'M1' designation as a dual carriageway road to Winchelsea (opened 2015).

The section from Geelong to Warrnambool runs inland, and so avoids the slower, but scenic Great Ocean Road.

At Mount Gambier the highway takes a more northward tack as the coast curves to the northwest, passing the Coorong National Park.

Shortly before Tailem Bend it is joined by Dukes Highway, part of the main route between Melbourne and Adelaide.

It continues north-west via Glen Osmond Road to eventually terminate just south of the Adelaide city centre.

The section of Princes Highway between West Helensburgh and Bulli Tops was the original coastal route between Sydney and Wollongong, first used in 1843.

The original submissions in January 1920 were in order for the Prince to have the opportunity during his visit to make the trip from Melbourne to Sydney overland along the route.

[8] That idea never came to fruition, due partly to the limited amount of time and the cost of upgrading the road to a suitable standard for him to undertake the trip.

[9] The road from Sydney was opened in Bulli on 19 October, by the NSW Minister for Local Government, Thomas Mutch.

1 was declared along Prince's Highway on 8 August 1928, heading south from the City of Sydney through Sutherland, Wollongong, Nowra, Bateman's Bay and Eden to the southern boundary of the state towards Genoa in Victoria (for a total of 351.5 miles).

[24] At that time, the route from Adelaide was via Aldgate, Mylor, Macclesfield, Strathalbyn, and Langhorne Creek, crossing the Murray River at Wellington, then continuing along the present towns of Meningie, Kingston SE, Robe, Beachport, Millicent and Gambier Town (Mount Gambier).

[29] The passing of the Road Management Act 2004[30] through the Parliament of Victoria granted the responsibility of overall management and development of Victoria's major arterial roads to VicRoads: VicRoads re-declared the road in 2010 as Princes Highway West (Arterial #6500), beginning at the state border with South Australia to Geelong, then from Altona North to Parkville;[31] and in 2007 as Princes Highway East (Arterial #6510), beginning at the Melbourne CBD to Narre Warren, then from Yarragon to Trafalgar, then from Morwell to the state border with New South Wales.