The purpose of Austroads project NS1929 Review of sign sizes for electronic regulatory speed signs, is to undertake a domestic and international literature review to determine if the size of electronic regulatory speed signs (ERSS), such as variable speed limit signs, can be reduced from static sign size specifications without adversely impacting efficiency of driving or safety. A review of current practices found that the sizes of ERSS used in Australia are largely similar to that described in Australian Standard AS 1742.4, although some minor differences are identified in a few specific application areas, such as tunnels and managed motorways. rightness requirements and the minimum number of red annuli from jurisdictions largely follow AS 5156. However, the number of red annuli and the required number of flashing annuli during speed limit changes still vary amongst jurisdictional practices. Review of overseas literature and practices concluded that the size required for ERSSs are generally equivalent or larger than that of standard static speed signs. Many road agencies tend to recommend larger sign sizes and letter heights for ERSS than that of standard static speed signs (e.g. the UK Department for Transport, the US Department of Transportation, NZTA and RMS). This report details the review of current practice, following which a number of recommendations regarding ERSS were able to be made and agreed upon by the project working group. These recommendations are as follows: • Australian road agencies should adopt the static sign size and design requirements described in AS 1742.4, AS 1743 and AS 5156 for ERSS. When used in certain applications such as tunnels or on managed motorways, the size requirements shown in Table 5.1 should be considered. The illumination should be adjusted based on the lighting conditions, especially during daylight hours to reduce the incidence of flaring or the over-glow effect. When displaying the normal speed limit of the roadway, all pixel rings of the annulus should be illuminated. When displaying speeds other than the normal speed limit, the outermost ring of the red annulus shall be non-flashing in order to satisfy the regulatory status of the sign, and all other inner rings shall be flashing. • Austroads writes to Standards Australia informing of the recommendations detailed in this report and suggesting that as all electronic message displays are 'traffic control' signs of a regulatory, warning or guidance nature, the display component directed to road users only, should be determined by the appropriate Standards Australia Committee and be included in the AS 1742. • Austroads and the Traffic Management Working Group (TMWG) consider incorporating these recommendations and amendments into the next revision of the Austroads Guide to Traffic Management (AGTM) - Part 5 Section 5: Speed limit, AGTM- Part 10 Section 5: Electronic signs and any other relevant parts of the AGTM where appropriate. • Asset procurement and operation and maintenance costs of ERSS could be reduced through the development of new technologies, rather than through the use of a smaller sign size. • Austroads is interested in the progress of the AASHTO proposed research project 'LED applications for enhancement of traffic control signs'. It is recommended that ARRB have a watching brief on this AASHTO project and report relevant results to the Network Task Force. (Author/publisher)
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