The department is responsible for the effective management and efficient operation of all state government roads.
Before it is possible to plan improvements to the road system, it is important to understand how people currently use the existing network of roads.
Traffic volume information is an important indicator of how the network is used.
An interactive map displaying traffic volume estimate information for arterial roads in South Australia is available from the Location SA Map Viewer. Volumes are shown by various colour bands, click the 'Legend' button for more information.
Clicking on any coloured road section gives, amongst other things, the estimated average number of vehicles per day (two-way) that travel on that road section (shown as ‘Tesecn Volume’), the year of the oldest survey used to derive that estimate (‘Tesecn Base Year’), and the percentage and numbers of commercial vehicles (‘Cv Percent’ and ‘Number Cvs’ respectively).
The Average Annual Daily Traffic (AADT) estimate represents the total volume of traffic (that is, the sum of traffic travelling in both directions on a two-way road) passing a roadside observation point over the period of a full year, divided by the number of days in the year.
Heavy vehicle traffic estimates represent the average daily two-way volume of these vehicles, and are expressed on the maps as both an absolute number and a percentage proportion of the total traffic flow. Heavy vehicles are defined as being those vehicles that are included in Classes 3 to 12 inclusive of the AUSTROADS vehicle classification system.
In general, this map shows traffic estimates only for sealed roads that are maintained by the department. However, estimates are progressively being provided for certain outback unsealed roads whose management is also the responsibility of the department.
To achieve a reasonable balance between accuracy and practicality, the road network has been broken down into a series of "traffic estimate sections". These are defined as discrete sections of road where the actual values of traffic volumes anywhere along that section are unlikely to vary by more than 10-15 per cent from the value shown on the map for that particular section.
The information represented on this map is derived from a comprehensive database which facilitates the integration of various data sources.
There is also a series of older static maps available (last updated 2015) which display estimated traffic volumes on arterial roads. They cover both rural and metropolitan areas of the State. These maps are no longer being maintained.