There are locations on the road network where a number of critical messages need to be conveyed over a short time/distance framework where sign co-location might be attractive to road agencies as it provides opportunity to make full use of existing or proposed gantries without leaving out any important information. However, the amount of information that is likely to be displayed on the sign arrays may exceed road users’ capacity to absorb and act on them. The Austroads project NT1782 ‘Ability to Absorb Information through Electronic and Static Signs’ aims to investigate how easily different messages displayed on co-located signs can be absorbed, and if drivers can absorb messages and take appropriate action without any adverse impact on the safety and efficiency of driving. The project reviewed current practices and research evidence on sign co-location and employed an advanced driving simulator (ADS) from the Centre for Accident Research and Road Safety (CARRS-Q) to further investigate the possible impacts of sign co-location on drivers’ responses and behaviour in an emergency situation. Co-location of three types of signs under motorway conditions were investigated: direction signs (DS), variable message signs (VMS) and variable speed limits/lane control signs (VSL/LCS). The research found that although some standards and guidelines do not permit co-location of sign information, these appear to have been overtaken by current practice and more recent guidelines from some jurisdictions. More recent guidelines recommend co-location; the European EasyWay guidelines allow a large number of different formats. Studies of driver opinion have found high levels of satisfaction with new forms of complex signs. Experimental and simulator studies have found that drivers have been able to cope well with the amount of information likely to be presented on colocated signs and to be able to extract the required information from the sign array in time to make the required decisions. The ADS study showed that neither dual nor triple co-location appeared to affect driver behaviour during standard driving, speed limit change, and lane closure situations, and that drivers coped well with emergency situations. Drivers appeared equally able to select the correct destination whether signs were co-located or not, although they did not always capture all the information from co-located signs. Few aspects of the driving task were adversely affected with triple co-location of signs. More drivers exceeded the speed limit at ‘check points’ on the simulated driving route, but overall speeds were no higher, suggesting that the differences in speeds were small. In general, drivers responded adequately to simulated emergency, although there was some suggestion that some responses may have been slower with triple co-location. It is concluded that dual co-location of VSL/LCS, VMS and/or DS is a practical arrangement which has been widely practised overseas and in Australia. Triple co-location of VSL/LCS, VMS and DS is also practised overseas but is still new to the Australian driving community. Although there is no clear evidence showing that triple co-location gives rise to riskier behaviour, this proposition should be viewed with caution. Further evaluation of triple co-location in a real-life setting is called for. Triple colocated signs should be used only in situations where other arrangements for displaying essential sign information are impractical. Driver behaviour should be monitored closely in the period following installation. It is therefore recommended that Austroads incorporate the consideration of dual colocation into the next revision of Guide to Traffic Management — Part 10 (Austroads 2009b), and also inform Standards Australia so that relevant Australian standards may be updated to reflect this recommendation. It is also suggested that Austroads should develop further guidelines on the consistent design of co-located signs, particularly on the special requirements for VMS design when it is co-located with other dynamic and static signs. (Author/publisher)
Samenvatting