This deliverable describes a draft version of a tool that has been developed within ERASER Work Package 3 (Road authorities pilot) to help European road authorities make decisions to improve the safety and ‘self-explainingness’ of their roads. For this tool, the concept of self-explaining roads (SER) has been taken forward in relation to speed: the design of a road can provide explicit cues to road users about what the speed limit might be, and may also implicitly and intuitively evoke a sense of appropriate speed. It is suggested that various characteristics of a road may act as accelerators or decelerators, giving road users the impression of a faster or slower road; a self-explaining road will have characteristics that are in line with the speed limit on the road and the speed limit will therefore be credible. The aim of the tool is not just to make roads and their speed limits more credible or self explaining, but also to ensure that speed limits are safe. The tool is grounded in the ‘safe system’ approach. In Sweden and the Netherlands, where the safe system approach has already been embraced, ‘safe’ speeds have been defined in order to improve the ‘system’ such that crashes are survivable. The tool that has been developed requires that road characteristic data are entered and, on this basis, the tool calculates what would be a ‘safe speed’ (i.e. survivable) and assesses whether the speed limit is credible. This deliverable describes the variables that could be used in a tool for self-explanatory and safe roads, and details the basis upon which a safe speed and credible speed assessment can be made. For this project, the ERASER tool has been developed to be used on rural roads, since these roads have been the focus of the ERA-Net programme. Care was also taken to develop a tool that did not require intensive data collection (in recognition that not all road authorities are ready for GIS-based tools that require significant data). As such the data required is relatively light and this version works on a road-by-road basis rather than across a whole network. In order to gain feedback on the direction of the development of the tool, a functionality and usability check was undertaken to better understand how the tool might be used by road authorities, what functionality should be included and whether the tool was useable. The functionality and usability check found that most authorities were content with the basis and style of the tool. Suggestions were made for changes, however, most of these suggestions were in the direction of more detail and more fine-tuning, which might be taken into account in a next version of the tool. The road authority representatives did not always agree in their comments: some road authorities plead for more detail in order to be more precise, others were more in favour of less detailed options. This may highlight the need for future work to be tailored to the needs of specific road authorities and in accordance with data availability. It may be feasible in the future to progress two different tools — one that has relatively light data requirements, and one that requires more detail, but can provide more accurate outputs. Based on the comments of the road authorities, the ERASER tool has been improved by improving the precision of data requirements and improving the indication of categories within the data-input where needed. Other suggestions that were made — for instance the wish to include more speed comparisons and a network-wide approach - might be taken into account if a more extended version of the tool will be developed. (Author/publisher)
Abstract