State of the art report on existing treatments for the design of forgiving roadsides

IRDES (Improving Roadside Design to Forgive Human Errors) is a research project of the cross-border funded joint research programme "ENR SRO1 - Safety at the Heart of Road Design", which is a trans-national joint research programme that was initiated by "ERA-NET ROAD - Coordination and Implementation of Road Research in Europe" (ENR), a Coordination Action in the 6th Framework Programme of the EC. The funding partners of this cross-border funded Joint Research Programme are the National Road Administrations (NRA) of Austria, Belgium, Finland, Hungary, Germany, Ireland, Netherlands, Norway, Slovenia, Sweden and United Kingdom. Analyses of fatal road accidents in the European Union show that 45 percent are single vehicle accidents. These accidents are primarily classified as run-off-road accidents, where the vehicle leaves the road and enters the roadside. A roadside is called unforgiving, if hazardous objects such as trees are placed in an inappropriate distance to the road so that the risk of severe accidents is increased. The European road directors declared the implementation of forgiving roadsides as one of the most promising short-term measures to increase road safety. The purpose of this concept is to avoid crashes of errant vehicles or to minimize crash consequences. The goal of work package one of the IRDES project is to collect and harmonize common standards and guidelines for roadside treatments. Initially, this deliverable introduces typical roadside hazards, which are the basis for appropriate counter-measures. The main part of this report comprises results and findings of relevant literature, guidelines and standards dealing with roadside treatments. Summarizing the literature study, three categories of treatments are proposed: 1. The removing or relocation of potentially dangerous roadside objects 2. The modification of roadside objects or design 3. The shielding of roadside objects These three categories determine the main structure of the report. The first category mainly comprises recommendations for so-called safety zones. These are obstacle-free areas beyond the travel lane in order to avoid collisions. Additionally, these zones assist drivers to perform easy recovery manoeuvres. Especially for road planning, an appropriate safety zone should be considered. If hazardous obstacles cannot be removed or relocated, they need to be modified. Crashworthy structures or breakaway devices are common examples for modifications. Moreover, the design of slopes and ditches are relevant factors for a safe road. In many cases, removing or modifying hazardous objects is not possible or economically advisable. Isolating or shielding the drivers from the respective objects helps to minimize the severity of a crash. Safety barriers and attenuators at bridge abutments are good examples for this kind of treatment. The output of this deliverable is a harmonized collection of state-of-the-art treatments to make roadsides forgiving. In further work packages of IRDES, the effectiveness of the treatments will be assessed by several methods. The final outcome of the IRDES project is a practical guideline for forgiving roadside design in Europe, referring to the results and findings of this report.