Assessing the need and cost-effectiveness of high-containment level safety barriers in Finland

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School of Engineering | Master's thesis
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Date

2010

Department

Insinööritieteiden ja arkkitehtuurin tiedekunta

Major/Subject

Tietekniikka

Mcode

Yhd-10

Degree programme

Language

en

Pages

156

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Abstract

The cost-effective use of passive roadside safety measures, such as safety barriers, is becoming more and more important. The Finnish Road Administration (FinnRA) is considering the replacement of conventional safety barriers with high-containment level safety barriers at certain roadsides. However, the practical need and cost-effectiveness of these safety barriers have yet not been evaluated. Therefore, an assessment method able to identify these issues has been developed in this thesis. The assessment method is intended to serve FinnRA as a decision making tool, to select between several safety barrier alternatives with different containment levels. The application of this assessment method is expected to foster a reduction of the number of fatal and serious single-vehicle accidents in Finland. A detailed literature study was conducted identifying the state-of-practice on safety barrier requirements, including the containment level selection, in Finland, Germany, Sweden and United Kingdom. Existing accident data from single-heavy vehicle accidents (SHVAs), which occurred in Finland during the years 2004 to 2007, was analyzed. Of particular interest were hereby all SHVAs that involved a safety barrier collision and occurred on a main road. A cost-benefit analysis (CBA), based on the existing accident data, was performed to determine the theoretical traffic volume thresholds of heavy vehicles for cost-effective H1/H2 barrier installations. A probabilistic accident severity assessment was conducted, providing the basis for a second CBA. The assessment was done within an expert panel, which used the Delphi Method in order to predict the probability and severity of the collision scenarios considered. The latter covered not only single-vehicle accidents (SVAs) of heavy vehicles, but of passenger cars as well. The assessment was used to determine the accident cost reduction or increase to be expected due to the H1/H2 barrier installations with respect to the N2 barrier installations. The results of the assessment-based CBA revealed at which of the considered roadside conditions the use of H1/H2 barriers appears to be cost-effective. The existing accident data analysis and both CBAs will form the basis of the proposed future assessment method. The literature study revealed that the Finnish guideline meets the European standard on safety barrier requirements. The analysis of the existing accident data showed that the annual number of SHVAs on main roads, and of those involving a safety barrier collision, is fortunately small. So are the resulting casualty numbers. The assessment-based CBA revealed that H1/H2 barriers are a cost-effective safety measure when installed at roadsides being especially hazardous. The use of Hl/H2 barriers at the general roadside on the other hand appears to be not cost-effective.

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Supervisor

Pellinen, Terhi

Thesis advisor

Valtonen, Jarkko

Keywords

safety barriers, containment level, heavy vehicle accidents, single vehicle accidents, cost-effectiveness, safety barrier regulations

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https://urn.fi/URN:NBN:fi:aalto-2020122356983

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[dipl] Insinööritieteiden korkeakoulu / ENG