On most French highways, hard shoulders are equipped with safety barriers to protect vehicles from running off the roadway from either punctual obstacles like bridge pillars, or in the presence of embankments or ditches for differences of level above 4 m. The research question is to determine if there would be a global safety gain to the user in systematically equipping all hard shoulders with safety barriers. The severity of run-off the road is measured and compared according to if they occur with a protected hard shoulder or a non-protected one, and in the latter case, whether what is off the road is at the same level, an embankment or a ditch. The safety indicator used is the presence of at least one casualty inside the vehicle running off the road. A Logistic model is used to take into account all the different relevant cofactors. The data relates to five years of observation - 1996 to 2000. The network comprises approximately 2,300 km of motorway located in plains. Three quarters of these roads have two lanes in each direction and one quarter has three lanes. Average traffic is between 10,000 and 60,000 vehicles per day, 10 to 20 per cent of which is trucks. A crash report form is completed when a vehicle on or off the motorway roadway cannot resume its journey without being towed away after a crash. All injury-crashes and damage-only crashes are recorded. Information is particularly detailed on the highway infrastructure and its part in the frequency and severity of accidents. The severity of run-off the road on hard shoulders is on average significantly higher in the absence of a safety barrier. Higher values of severity are connected with run-off the road in the presence of embankments or ditches (lower than 4 meters, as others have already systematically been equipped). These results take into account the typology of the accident (number of vehicles involved, different impacts, type of vehicle involved) and of highway characteristics. Despite there being less and less non equipped hard shoulders, severity differences are large enough to be significant, and confirm the results of previous research carried out from 1985 to 1995 on a part of the same network. Systematic equipment of highway hard shoulders appears to be beneficial as a whole within the infrastructure and European traffic conditions, with a better control of run-off the road consequences. Moreover, the subsequent suppression of most of the ends of guardrails should also increase safety. (A) For the covering abstract of the conference see ITRD no 207828. The reprints are also available at the web - http://www.vti.se/pdf/reports/K18APart1.pdf; http://www.vti.se/pdf/reports/K18APart2.pdf and http://www.vti.se/pdf/reports/K18APart3.pdf.
Samenvatting