INTERNATIONAL SEMINAR Desafío para el Diseño, Construcción y Operación LONG TUNNELS Challenges for Design, Construction and Operation PROGRESS IN RISK ASSESSMENT FOR PERFORMANCE-BASED ASSESSMENT OF ROAD TUNNEL SAFETY Bernhard Kohl, MSc ILF Consulting Engineers (Austria) 17, 18 y 19 de Octubre 2012 PIARC CHILE Santiago, Chile 1
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INTRODUCTION Bernhard Kohl, MSc ILF Consulting Engineers Head of branch office Linz (Austria) Member of PIARC TC3.3 • Leader of new WG “Feedback from experience on tunnel safety” • and former WG “Manage and improve tunnel safety” 3
OUTLINE (1) Basic principles of performance based approach (1) Basic principles of performance based approach (2) Risk analysis methods (3) Approach for risk evaluation (4) Practical application of risk analysis (5) Research activites and new developments (6) Conclusions 4
BASIC PRINCIPLES OF PERFORMANCE BASED APPROACH Basic principle of road tunnel safety: Holistic approach Safety / Maintenance Emergency Services Project Operational Management Procedures Traffic Management / Structural Vehicles / Drivers Engineering Ventilation Electric Infrastructure 5
BASIC PRINCIPLES OF PERFORMANCE BASED APPROACH Different approaches to road tunnel safety Prescriptive approach Risk based approach Frequency Consequences Risk 1.0E+01 1.0E+01 1.0E+00 1.0E+00 Gesamt Gesamt 1.0E-01 1.0E-01 Kollision Kollision Frequency Frequency Brand Brand 1.0E-02 1.0E-02 1.0E-03 1.0E-03 Häufigkeit pro Jahr und 1 km Häufigkeit pro Jahr und 1 km 1.0E-04 1.0E-04 x 1.0E-05 1.0E-05 = 1.0E-06 1.0E-06 1.0E-07 1.0E-07 1.0E-08 1.0E-08 1.0E-09 1.0E-09 1.0E-10 1.0E-10 1.0E-11 1.0E-11 1 1 10 10 100 100 1'000 1'000 Consequences Consequences Ausmass [Todesopfer] Ausmass [Todesopfer] R H A ( A ) G m ik ik k ik k i , k A tunnel is safe if it is designed A tunnel is safe if it meets in line with valid regulations predefined risk criteria • Technical specification of safety features of a • Structured, harmonised and holistic safety tunnel analysis – basis for decision making • Easy to implement, but scarcely taking • Consideration of specific characteristics of a specific characteristics into account tunnel • Residual risk (even if all requirements are met) • Quantitative evaluation of residual risk / of – is not addressed effects of safety measures 6
BASIC PRINCIPLES OF PERFORMANCE BASED APPROACH Different approaches to road tunnel safety Prescriptive based approach and risk based approach have to be used as complementary elements of the safety assessment process. 7
BASIC PRINCIPLES OF PERFORMANCE BASED APPROACH Risk assessment process RISK ASSESSMENT Start Start Risk analysis Definition of the system Definition of the system Report: Risk Analysis For Road Tunnels Hazard identification Hazard identification Probability analysis Probability analysis Consequence analysis Consequence analysis Risk estimation Risk estimation Risk evaluation Risk criteria Risk criteria Risk evaluation Risk evaluation Report: Risk Evaluation Risk reduction No (additional) (additional) Acceptable risk? Acceptable risk? safety measures safety measures Yes Stop Stop 8
BASIC PRINCIPLES OF PERFORMANCE BASED APPROACH Risk assessment process • Risk analysis: systematic approach to analyse sequences and interrelations in potential incidents or accidents, identifying weak points in the system and recognising possible improvement measures • Risk evaluation: directed towards the question of acceptability of the identified risks – judged against particular risk criteria that have been defined • Risk reduction: required if the estimated risk is considered as acceptable, additional safety measures have to be proposed to reduce risk. 9
BASIC PRINCIPLES OF PERFORMANCE BASED APPROACH Different types of risk Different types of risk can be addressed in a risk analyses: • Societal risk: harm to a specific group of people • Individual risk: harm to an individual person • Economical loss • Damage to environment • Damage to immaterial values Focus on societal risk of tunnel users 10
BASIC PRINCIPLES OF PERFORMANCE BASED APPROACH Different types of risk representation • Expected risk value (EV) long-term average number of statistically expected fatalities per year • FN diagram 1,00E+00 1,00E-01 shows magnitude of 1,00E-02 1,00E-03 consequences in relationship 1,00E-04 Frequency / per year 1,00E-05 to the (cumulated) 1,00E-06 frequency of a hazard 1,00E-07 1,00E-08 1,00E-09 1,00E-10 1,00E-11 1 10 100 1.000 10.000 Damage [fatalities] 11
OUTLINE (1) Basic principles of performance based approach (2) Risk analysis methods (2) Risk analysis methods (3) Approach for risk evaluation (4) Practical application of risk analysis (5) Research activites and new developments (6) Conclusions 12
RISK ANALYSIS METHODS • In general, there is a big variety of different approaches, methods and complex models combining various methododical components for specific tasks • For road tunnels in particular, there are two big families of methods • Qualitative or semiquantitative scenario based methods • Quantitative system-based methods 13
RISK ANALYSIS METHODS Qualitative or semiquantitative scenario based Approach: analyses a set of relevant scenarios obtaining information on frequency/consequences for each individual scenario Select Select Investigate effects Investigate effects Analyse development Analyse development optimize optimize relevant relevant and consequences and consequences of scenarios of scenarios design design scenarios scenarios of scenarios of scenarios scenario 1 scenario 1 scenario 2 scenario 2 scenario 3 scenario 3 eg. evacuation … 14
RISK ANALYSIS METHODS Quantitative system based Approach: investigates an overall system in an integrated process, obtaining risk values for the whole system Probability calculation- Probability calculation- Damage values – Damage values – Input parameters Input parameters Input parameter Input parameter Results Results Accident type Accident type Traffic composition Traffic composition scenario evolution scenario evolution Tunnel type, ventilation system, Tunnel type, ventilation system, Accident rates Accident rates Traffic volume Traffic volume vehicles involvements vehicles involvements Emergency exits Emergency exits Expected risk value Logical tree (fatalities/year) initial event accident scenarios dangerous goods fires Mechanical accidents RISK X mechanical ( statistics) accidents Risk distribution (F-N-Curve) (model results) 15
OUTLINE (1) Basic principles of performance based approach (2) Risk analysis methods (3) Approach for risk evaluation (3) Approach for risk evaluation (4) Practical application of risk analysis (5) Research activites and new developments (6) Conclusions 16
APPROACH FOR RISK EVALUATION Background of risk evaluation: • Risk analysis: “What might happen?” • Scientific process: Identification, structuring, assessment of probabilities and consequences • Risk evaluation: ”Is the risk acceptable?” • Socio-political process including ethical, political and societal aspects • Strongly influenced by risk perception • Risk perception: is influenced by many parameters such as perceived benefits , voluntariness , controllability or catastrophic potential No “right” or “wrong” risk evaluation criteria 17
APPROACH FOR RISK EVALUATION Basic principles for risk evaluation: • Absolute criteria risk is acceptable as long as assessed risk is lower than a defined absolute threshold 18
APPROACH FOR RISK EVALUATION Basic principles for risk evaluation: • Relative criteria acceptable risk level risk is acceptable, as long as assessed risk is lower than an established risk profile Concept of “Reference Tunnel”: theoretical tunnel similar to tunnel under assessment, but fully complying with all requirements, conditions etc. defined in relevant regulations. 19
APPROACH FOR RISK EVALUATION Basic Principles for risk evaluation: • Cost-effectiveness approach Comparison of efficiency Cost Cost of safety measures and their risk reduction Total Cost Total Cost potential A tunnel is safe, if all Optimum = Minimum Optimum = Minimum cost-effective measures are implemented Cost for S Cost for S afety Measures afety Measures Loss E Loss E xpenses xpenses Safety Measures Safety Measures 20
APPROACH FOR RISK EVALUATION Practical example for a relative approach: Evaluation of safety measures for existing tunnel Influence of mechanical ventilation in a unidirectional tunnel without ventilation Model tunnel: 0,6 km 1,00E+00 unidirectional; 5,09E-02 1,00E-01 70.000 veh/d; 1,00E-02 frequency of event per year and km vaulted cross 1,00E-03 section 1,00E-04 1,00E-05 1,00E-06 Tunnel 3n: 1,00E-07 natural 1,00E-08 ventilation 1,00E-09 2,60E-03 1,00E-10 Tunnel 3l: 1,00E-11 1 10 100 1.000 Tunnel 3n Tunnel 3l longitudinal consequences of event (fatalities) ventilation FN-curve (overall risk) EV (fire risk) 21
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