AS 1742.4:2020 pdf free.Manual of uniform traffic control devices Part 4: Speed controls.
2.1 General
2.1.1 Objective of speed management
The objective of speed management is to contribute to roaa satery, rnoniiity antI amenity on public roads by providing a system of speed limits that are compatible with the speed environment.
Speed limits should be set so as to encourage, as far as practicable, a uniform speed of travel and hence reduce the potential for conflicts due to speed differentials between vehicles. Excessive variation among vehicle speeds can indicate either an inappropriately set speed limit or that drivers’ perception of the speed environment is open to confusion. The second of these causes may require corrective action other than reassessment of the speed limit.
2.1.2 General principles
2.1.2.1 Determining speed limits
The following recommendations and requirements apply when determining speed limits:
(a) Speed limits shall be capable of being practically and equitably enforced by use of speed zones of adequate length, by limiting speed limit changes, and by clarity and frequency of signposting.
(b) Where the speed limit exceeds the maximum safe speed of travel due to an isolated geometric deficiency or hazard, advisory speed signs displayed in conjunction with the relevant warning signs in accordance with AS 1742.2 shall be used to advise drivers of the desired speed.
(c) Speed limit signs on unsealed roads have traditionally displayed the default urban or default rural limit. Jurisdiction supplements may provide guidance if other speed limits are to be permitted within that jurisdiction.
(d) All signposted speed limits shall be in multiples of 10 km/h (except for a variation in South Australia that allows 25 km/h in school zones and road work sites).
2.1.2.2 Installation of speed limit signs
The following recommendations and requirements apply when installing speed limit signs:
(a) Speed limit signs shall be located at speed zone changes and boundaries of default limits. Special attention is required in siting such signs to ensure that they are prominently displayed to approaching drivers.
(b) Signs are normally installed on the left side of the roadway. At speed zone changes (typically speed reductions) and boundaries of default limits, signs should be duplicated on the right side. Signs may also be duplicated on the right hand side of a multilane carriageway.
(c) Attention is needed in locating signs to ensure that they do not obscure one another or otherwise obscure visibility, particularly at intersections.
(d) No other sign should be installed on any post carrying a speed limit sign unless it is a sign specified for auxiliary use with a speed limit sign in either this or another Australian Standard. Where it becomes necessary to convey two or more different messages at the one location, separate signs located a minimum of 0.6 V85 metres apart should be used.AS 1742.4 pdf download.