All country highways are signed or labelled with an M, A, B or C number. This is known as the Statewide Route Numbering Scheme (SRNS). The letter is given to a road based on the function and quality of the route.
‘M’ roads provide the primary road links that sustain economic and regional development in Victoria. They connect Melbourne and other capital cities and link major centres of production and manufacturing with Victorian ports. ‘M’ roads should provide a consistently high standard of driving conditions with divided carriageways, four or more traffic lanes, sealed shoulders and with linemarking and guideposts that are easily visible in all weather conditions. For example the Hume Freeway is signed the M31.
A roads serve the same role as ‘M’ roads but carry less traffic and are usually two-lane two-way roads. ‘A’ roads provide a similar consistently high standard of driving conditions on a single carriageway. Shoulder sealing should be provided on all ‘A’ roads and overtaking lanes should be constructed on all strategic freight routes and roads with daily traffic volumes of more than 2,000 vehicles. For example parts of the Princes Highway are signed the A1.
B roads provide the primary link between major regions not served by ‘A’ roads and to significant tourist centres. ‘B’ roads should have sealed pavements wide enough for two traffic lanes, with good centreline and edge linemarking, shoulders and a high standard of guidepost delineation. Additional overtaking lanes should be provided on higher volume ‘B’ roads to improve road safety and capacity. For example the Murray Valley Highway is signed the B400.
C roads provide the most important links between other centres of population, and between these centres and the primary transport network. ‘C’ roads will generally be two lane sealed roads with shoulders. The safety features will be determined on the basis of cost effectiveness, depending on traffic and terrain, crash records, load restrictions and frequency of flooding. For example Kilmore- Lancefield Road is the C324.
Visit VicRoads for more information on the statewide route numbering scheme.