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

LINKS TO SITES ON ROAD SYSTEMS AND ROAD DESIGN STANDARDS.

Information on AMCORD (The Australian Model Code for Residential Development) is contained on a Web page maintained by the Commonwealth Department of Transport, particularly under the section Good Living Spaces.

Page last modified 7 July 1999.