Based on a detailed analysis and considering foreign studies on this issue, the roadway sections it is needed to assess subdividing of road restraint systems into the conventional systems according to the ASTRA guidelines, concrete barriers and steel barriers.
The objective of this research project is the evaluation of the common safety barriers (road restraint systems) used in general in central reserves of Swiss motorways with regard to the criteria's traffic safety, maintenance and requirements of the norms and guidelines.
The research work gives basics for an entire assessment of road restraint systems which are used in the central reserve of Swiss highways. Decisive matrixes for the use of different systems (safety barriers according to ASTRA guideline, steel barriers and concrete barriers) will be evaluated considering safety, constructional and internal/financial criteria's. In addition to the norm SN 640 561 and guidelines these matrixes shall help the project planner to decide on a system.
The project was developed during the following Phases:
- Phase I: identifying those to be examined sections, of existing systems, route characteristics, procurement of accidents and maintenance specifications.
- Phase II: Evaluation and assessment of the data in the form of an interim report
- Phase III: Comparison with foreign studies (D and F), provide decision matrices and checklists
- Phase IV: Preparation of the final report
A survey of all accidents at safety barriers in central reserves of eight different motorway sections for the period of 2003 to 2007 as well as the determination of the systems in combination with the injuries and the types of vehicles was carried out.
The sections of the motorways were selected in the way that a representative average of common safety barriers generally used as well as connections between the types of accidents and the road’s characteristics (average daily traffic volume, numbers of lanes, course of the road, etc.) was evaluated and compared.
The focus of this research project was on the connection between the personal injuries and the different types of safety barriers.
The detailed analysis shows that the common safety barriers used in central reserves of Swiss motorways are, with regard to the passenger’s injuries sustained in an accident, analogous to the ones evaluated during performance tests according to norm SN 640 567-2. Safety barriers in central reserves of Swiss motorways which meet class A of the level of impact severity according to norm SN 640 567-2, are rated better with regard to the occurrence of personal injuries in a real accident than safety barriers of impact severity level B or C.
Based on the research results the requirements of the norm SN 640 561 regarding the choice and appropriate use of safety barriers in central reserves of motorways for containment level (H1), class of working width (W6) and impact severity level (A) are to be considered as appropriate. As a consequence, an adaption of the norm SN 640 561 is not required in these points.
This also applies to the safety barriers listed in the guideline for road restraint systems of the Swiss Federal Roads Office FEDRO and their performance classes (containment level, class of working width, level of impact severity).
Furthermore, data regarding the maintenance and repair costs of the safety barriers used on the selected motorway sections were collected, as far as they were existing and useful. Here it turned out that due to incomplete and no existing data only the average repair costs of the systems could be calculated.