It is a part of the National Highway network linking the state capital cities of Adelaide, SA, and Melbourne, Victoria, and is signed as route M1.

As it traverses across – and through, in one section, via the Heysen Tunnels – the Adelaide Hills, and due the fact the freeway is a major freight route, it also features arrester beds and concrete median barriers, with street lighting between Glen Osmond and Crafers.

The freeway narrows to four lanes just before it bypasses Crafers, and continues in a south-easterly direction, past Stirling, Hahndorf and Mount Barker, before narrowing further to a two-lane, single-carriageway, crossing the Murray River over the Swanport Bridge, to terminate just east of the crossing in Long Flat, south-east of Murray Bridge.

Prior to the initial construction of the freeway in the 1960s, inbound and outbound road traffic between Adelaide and south-eastern South Australia or Victoria used a two-lane highway originally built in the early part of the 20th century.

Studies began in 1962 for a freeway commencing from Crafers, that endpoint selected arguably due to the massive expenditure required with the precedent upgrade of the Mount Barker Road.

The tightest hairpin turn on the Mount Barker Road was infamous as the Devil's Elbow, often the site of car and semi-trailer accidents.

[10] The Freeway bypasses many towns previously along the Princes Highway, including: Shortly after the Adelaide–Crafers section opened, several incidents involving semi-trailers drew media attention to the road.

While the previous Mount Barker Road was a notorious stretch, its dangers were well known; the new freeway presented the new challenge of a sustained continuous gradient with traffic lights at the bottom.

In 2010 and 2011, after more incidents involving trucks having problems successfully braking down the hill, including one going into a bus stop, and another going straight through the intersection at the bottom, the government added new laws that any vehicle with 5 axles or more must stay in the left lane and must not exceed a 60 km/h limit from the interchange at Crafers to the old tollhouse.