The purpose of this Austroads technical research project ST1863 is to determine whether a technical solution is available that can identify heavy vehicles, their speed and configuration, and provide appropriate early warning of unsafe operation on descents. This project is not about enforcement, but rather determining if there are technological ‘smart’ advisory solutions to provide early warning to drivers of heavy vehicles. The review looks at infrastructure-based, vehicle-based and infrastructureto-vehicle smart solutions, instead of passive systems such as truck escape ramps and safety ramps (also known as arrester beds). It is intended that the smart solution will complement rather than replace these physical measures. This report details a literature review of overseas trials and applications of infrastructure-based smart technical solutions to this issue. A small number of applicable existing intelligent transport system (ITS) technologies have been installed in North America to assist heavy vehicles on long, steep slopes. A small number of downhill truck warning systems have been reviewed in the report, along with similar technologies such as a signal pre-emption system and truck rollover warning systems. A number of reports detailing the use of infrared cameras to determine the condition of heavy vehicle brakes were also reviewed, though it was found that the systems which had been reviewed would be of little benefit in a steep descent advanced warning system. While there have been few official impact studies of the systems, they have indicated a positive effect on driver behaviour and speed, with a positive public perception of the systems’ effects on safety. These results suggest that an advanced warning system could provide safety benefits at an appropriate trial site. This report also examined the applicability of in-vehicle technologies and co-operative intelligent transport systems (C-ITS) as advanced warning systems for heavy commercial vehicles on steep descents. The use of these technologies to provide advanced warning has become more viable in recent times due to recent advancements in in-vehicle technologies, which have helped to lower costs. A search of the literature did not find any trials, studies or applications specifically aimed at heavy vehicles on steep descents and making use of in-vehicle technologies or C-ITS. A number of technologies which could be adapted to provide advanced warning on steep descents were examined in this literature review, including in-vehicle telematics, on-board mass monitoring, geo-fencing, Intelligent Speed Adaptation (ISA), and dedicated short range communication (DSRC). Based on general claims about the technical capabilities of these technologies, the review was able to identify, on an elementary level, how they may serve as a warning system to heavy vehicle drivers on steep descents and possibly intervene by activating vehicle systems such as the braking system. In-vehicle telematics and C-ITS have been shown to have the potential to provide advanced warnings to drivers of heavy vehicles on steep descents. Of the in-vehicle telematics and C-ITS systems reviewed, incorporating a warning system into existing in-vehicle technologies, such as smartphones, navigation systems or a Transport Certification Australia (TCA) compliant intelligent access program (IAP) monitoring device, show the most promise. Communication was made with a number of in-vehicle telematics providers who all indicated that their telematics devices did not currently have steep grade warning functionality for heavy vehicles. While the telematics devices did not have a steep grades function, a number of telematics providers indicated that it could be a worthwhile addition. The review of the literature found no trials for invehicle telematics and geo-fencing for steep descents or curve warnings; therefore, no information regarding the costs and benefits have been published. As a result, the economic and safety benefits of vehicle-based and co-operative technologies are very difficult to quantify. This report also details a heavy vehicle thermal brake model used to examine the effect of changing a number of variables on the temperature of a vehicle’s braking system as the vehicle travelled down a steep downgrade. The parameters examined included road grade, vehicle speed, retardation level and vehicle mass. The study found that the vehicle mass and grade had the largest effect on brake temperatures, while retardation power and vehicle speed had a lesser, but still significant effect. This shows that it is important to include vehicle mass in any technological solution to the issue of heavy vehicles on steep descents, and that a system using an estimate of vehicle mass based on axle configuration would either produce a number of false warnings, or not provide a warning when it should. Weigh-in-motion systems can be used in infrastructure-based systems to help determine safe speeds for heavy vehicles on steep descents. Estimating vehicle mass by using a vehicle classification method was determined to not be accurate as there can be large variation between laden and unladen vehicle masses. At present, a number of co-operative and vehicle-based systems do not factor in vehicle mass, and as such would need to be adapted in order to incorporate vehicle mass. This study was also able to compile a limited database of steep grades, including information on the length of section, the maximum grade of the section, the average grade of the section, and the GPS coordinates of the start and end of the section. (Author/publisher)
Samenvatting