1. Road Systems and Design Standards
1.1 Introduction
Classification of roads needed to:
- identify body responsible for road,
- identify appropriate characteristics of the
road and its traffic,
- decide allocation of priority for installing
traffic control devices,
- set design standards for new roads,
- identify location of major traffic generators,
control degree of access along a road, and
- enable designation of major vehicle routes,
including heavy vehicle routes.
Standards for design of various classes of road set
forth by various road authorities. Publications include:
- Rural Road Design - Guide to the Geometric
Design of Rural Roads (Produced by Austroads)
- Urban Road Design (Produced by Department
of Main Roads, Queensland)
- AMCORD (The Australian Model Code for Residential
Development) (Production sponsored by Commonwealth Department of Housing and
Regional Development)
- Queensland Streets: Design Guidelines for
Subdivisional Streetworks (Produced by The Institute of Municipal Engineering
Australia, Queensland Division)
1.2 Road Classification Systems
Roads and streets exist to serve two major purposes:
- Mobility
- Access to abutting land uses
These two purposes often conflict e.g. traffic along
an arterial road is hindered in its mobility by the needs of people to park
along the road, and to enter and leave the road from adjoining properties.
In practice most roads must serve a mix of these
two functions but the type of road determines the mix of the two functions.
Three broad categories of road can therefore be used:
- Arterial Roads - where the major function
is mobility,
- Local Streets - where the major function is
access to properties, and
- Intermediate Streets - where both mobility
and access are prime functions.
Roads in the Intermediate Streets category are generally
termed Collector or Distributor roads.
1.3 Road Design Standards
Design standards for roads vary from one road authority
to another, from one type of road to another, and from one country to another.
Typical major design features are as follows.
- Freeways
- Major function mobility
- Design speed 80 to 100 km/h
- Multilane divided roads
- High-volume traffic
- Complete control of access
- Intersections grade separated
- Arterial Roads
- Primary function mobility
- Design speed 60 to 100 km/h
- Intersections controlled by traffic signals,
interchanges or roundabouts
- Typically divided carriageway with 2 or more
lanes for each direction of flow
- Controlled frontage access with only major
generators permitted access
- Sub-arterial Roads
- Primary function feeder roads
- Intersections: uncontrolled T junctions with
sub-arterial on run-of-tee
- Design speed 60 km/h
- On road parking discouraged
- Residential Streets
- Primary function access for vehicles, pedestrians
and cyclists
- Other functions: corridors for physical infrastructure
eg water mains, encouraging social interaction
- Types:
- Access Place
- Access Street
- Collector Street
- Trunk Collector Street
- Rural Residential Streets
- Industrial Streets
Page last modified 9 June 2005.