WIT Press

Optimization Of Risk Criteria For Road Tunnels


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M. Holický


Available documents concerning risk management and assessment of road tunnels provide almost no guidance on risk criteria. Three different types of risk are discussed in the submitted paper: individual risk Rind of a person related to specific operational conditions, expected risk Rexp expressed in terms of number of fatalities per tunnel and year and societal risk expressed in terms of cumulative frequency F = P(Rm ≥ N), presented commonly as F - N curve, per tunnel (or 1 km of a tunnel) and year. Recommendations for quantitative risk criteria are derived from commonly accepted safety requirements. The ALARP concept is generally accepted for the specification of the lower and upper bounds of relevant risk indicators. The lower and upper bounds of an individual risk are within the interval from 10−3 to 10−6 per year and tunnel. The expected risk is to be anticipated around one fatality per tunnel and year. The societal risk is commonly compared with the F - N curve given by a power function A N−k, where the cumulative frequency A is within the interval from 0,0001 to 0,1 and the parameter k within the interval from 1 to 2. Further it is shown that expected risk Rexp can be used to minimize the total consequences including consequences of unfavourable events and costs of safety measures (for example escape routes). It appears that the assumed life time and discount rate may significantly affect the total consequences and the optimum arrangements of the road tunnels. Keywords: risk, criteria, road, tunnels, optimization. 1 Introduction Road tunnels represent complex technical systems that may be exposed to hazard situations leading to serious consequences. Risk criteria for road tunnels are therefore becoming a more and more important issue all over the word. The increasing interest in tunnel safety caused by recent tragic events in several European road tunnels resulted in an effort to take consequences of unfavorable


risk, criteria, road, tunnels, optimization.