1. Center for Risk Management of Engineering Systems University of Virginia, Charlottesville 151 Safety Judgment of acceptability of risk Subjective component –Evaluates whether a given risk is acceptable –Policies based on that judgment –Policies determine trade off between a level of risk and resources needed to reduce the risk Objective component –Risk assessment (Lanzilotta, 1995)

2. Center for Risk Management of Engineering Systems University of Virginia, Charlottesville 152 Evidence for Risk Traditional knowledge Common-sense assessment Analogy to well known cases Experiments with human subjects Review of inadvertent occupational hazard Statistical analysis Experiments on non-human organisms Tests of product performance (Lowrance, 1976)

3. Center for Risk Management of Engineering Systems University of Virginia, Charlottesville 153 Investigating Risk Conditions of exposure Identify the adverse effect Relate exposure with risk Estimate overall risk (Lowrance, 1976)

4. Center for Risk Management of Engineering Systems University of Virginia, Charlottesville 154 Transportation Risk Assessment Probability –Likelihood of an accident –All events that lead to the accident Severity –Outcome of an accident –All events after the accident occurs

5. Center for Risk Management of Engineering Systems University of Virginia, Charlottesville 155 Transportation Risk Assessment (cont.) Risk probability varies as a function of the state of the system State of the vehicle State of the environment A system state is the result of several conditions Driver error Machinery failures Roadside hazards (Lanzilotta, 1995)

6. Center for Risk Management of Engineering Systems University of Virginia, Charlottesville 156 Difficulties of Estimating Transportation Risk Probability Accidents are rare events and difficult to predict Little attention to the time period preceding the accident Compound set of hazards and events leads to the accident (Lanzilotta, 1995)

7. Center for Risk Management of Engineering Systems University of Virginia, Charlottesville 157 Safety State Model Near collisions are more common than accidents Identify near collisions and events that lead to them Formulate response to reduce occurrence of near collisions Reduce number of accidents (Lanzilotta, 1995)

8. Center for Risk Management of Engineering Systems University of Virginia, Charlottesville 158 Accident Statistics Disadvantages –Unreported accidents –Severity iceberg –First and most harmful event –Fatalities do not occur frequently enough to be statistically predictive –Random nature of road accidents (Adams, 1996), (Michie and Bronsted, 1994)

9. Center for Risk Management of Engineering Systems University of Virginia, Charlottesville 159 Accident Statistics (cont.) Advantages –Available and assessable –Factual –Public interest

10. Center for Risk Management of Engineering Systems University of Virginia, Charlottesville 160 Examination of HTRIS Compare date gathering methodologies using HTRIS Guide to collecting data from HTRIS Capabilities available in HTRIS Alternatives to HTRIS

11. Center for Risk Management of Engineering Systems University of Virginia, Charlottesville 161 Methods to Gather Accident Data All accidents between two nodes –Reveals all accidents –Manually eliminate irrelevant accident data All fixed object accidents between two nodes –Reveals fewer accidents by targeting relevant accidents –Other accidents involving guardrail might be overlooked

12. Center for Risk Management of Engineering Systems University of Virginia, Charlottesville 162 Methods to Gather Accident Data (cont.) All run-off the road accidents between two nodes –Reveals fewer accidents by targeting relevant accidents –Other accidents involving guardrail might be overlooked Comprehensive method –Provides comprehensive data –Inefficient and time consuming

13. Center for Risk Management of Engineering Systems University of Virginia, Charlottesville 163 Guide to Collecting Data Enter HTRIS Enter ‘x’ at first node Enter ‘y’ at furthest node within five miles of first node Press F 6 when done Enter ‘x’ at first node Enter ‘y’ at last node Press F 6 when done Is the furthest node less than five miles away from the first node? Enter ‘y’ for node list Enter County Code at “jurisdiction” prompt Enter Road ID Press F 10 for node locator Type ‘y’ to see individual accidents Press F 6 to analyze all accidents Hit enter to see summary statistics Hit enter to see Accident Record Inquiry if more information is desired Hit enter to see Vehicle Record Inquiry if more information is required Repeat process for the remaining node on road (if nodes were more than five mikes away), placing an ‘x’ at the node that previously had a ‘y’ and a y at the furthest node within five miles. YESNO

14. Center for Risk Management of Engineering Systems University of Virginia, Charlottesville 164 Data Available from HTRIS Summary statistics Individual accidents Accident Record Vehicle Record

15. Center for Risk Management of Engineering Systems University of Virginia, Charlottesville 165 Summary Statistics ParameterExplanationSignificance Fatal Accidents The number of accidents involving fatalities that have occurred in the specified corridor information on exposure Injury Accidents The number of accidents involving injuries that have occurred in the specified corridor information on exposure PD accidentsThe number of accidents involving property damage that have occurred in the specified corridor information on exposure Persons killed The number of fatalities that have occurred in the specified corridor information on severity Persons injured The number of injuries that have occurred in the specified corridor information on severity Amount of PD The amount of property damage that has occurred in the specified corridor information on severity Total Accidents The number of accidents that have occurred in the specified corridor information on exposure

16. Center for Risk Management of Engineering Systems University of Virginia, Charlottesville 166 Individual Accidents ParameterExplanationSignificance Document Number The number used by the police department to identify the accident Will be useful if more detail information on the accident is needed. DateThe date the accident occurred Offset from Node The distance in miles from the accident to the node Useful for evaluation to compare precise locations DirectionThe direction the vehicle was traveling at time of accident Useful for evaluation to compare precise locations. Collision Type The numerical code for type of collision Useful for screening and evaluation phase to show the type of collisions that relate to presence or absence of guardrail. WeatherThe numerical code relating to the weather at the time of accident Might be useful for evaluation and determination of safety countermeasures by giving information on accident trends.

17. Center for Risk Management of Engineering Systems University of Virginia, Charlottesville 167 Individual Accidents (cont.) ParameterExplanationSignificance Surface Condition The condition of the road surface at the time of the accident Might be useful for evaluation and determination of safety countermeasures by giving information on accident trends. Number of Vehicles The number of vehicles involved in the accident Might be useful for screening and evaluation to determine the relevance of guardrail Number of fatalities The number of fatalities involved in the accident Useful for evaluation by providing information on severity Number of pedestrian fatalities The number of pedestrians killed due to the accident Number of injuries The number of injuries involved in the accident Useful for evaluation by providing information on severity Number of pedestrian injuries The number of pedestrians injured due to the accident

18. Center for Risk Management of Engineering Systems University of Virginia, Charlottesville 168 Accident Record ParameterExplanationSignificance Document Number The number used by the police department to identify the accident Redundant – information available in summary statistics Road System Distinguishes between primary and secondary roads Useful for distinguishing between primary and secondary CountyThe county the accident occurredUseful for obtaining accidents specific to a particular county Intersect Route The Intersection RouteUseful for screening by providing information on the routes OffsetThe distance in miles from the accident to the node Redundant – information available in summary statistics Number of lanes The number of lanes on the route Facility Type The type of road Road Defects Defects on the roadUseful for evaluation – may reveal the significance of guardrail Type of Collision The type of collisionRedundant – information available in summary statistics

19. Center for Risk Management of Engineering Systems University of Virginia, Charlottesville 169 Accident Record (cont.) ParameterExplanationSignificance # vehiclesThe number of vehiclesRedundant # killedThe number of fatalitiesRedundant # injuredThe number of injuriesRedundant Type of environment DateThe date the accident occurredRedundant RouteThe route the accident occurred onUseful for screening CityThe city the accident occurred in Node Surface Width Surface Type The surface of the road Traffic Control The traffic controlMight be useful for evaluation and determining countermeasures SeverityThe severity of the accidentInformation on the adverse effects

20. Center for Risk Management of Engineering Systems University of Virginia, Charlottesville 170 Accident Record (cont.) ParameterExplanationSignificance WeatherThe numerical code relating to the weather at the time of accident Redundant – information available in summary statistics Pedestrians killed The number of pedestrians killed due to the accident Redundant – information available in summary statistics Pedestrians Injured The number of pedestrians injured due to the accident Redundant – information available in summary statistics Property Damage The amount of property damage involved in the accident Useful for evaluation by providing information on adverse effects Accident lane Number The lane the accident occurredMight be useful for evaluation by revealing the relevance of guardrail TimeThe time the accident occurredMight be useful for evaluation and determining countermeasures by revealing trends

21. Center for Risk Management of Engineering Systems University of Virginia, Charlottesville 171 Accident Record (cont.) ParameterExplanationSignificance DistrictThe district of the accident Shoulder Width The width of the shoulder where the accident occurred Useful for evaluation by describing the location Surface Condition The condition of the road surface at the time of the accident Redundant – information available in summary statistics Alignment(Curve, dip, grade, hillcrest, not stated, other, straight) Useful for evaluation in determining exposure Major factor The most contributing factor to the accident Might be useful for evaluation and determining countermeasures Zone of Impact What is this? LightThe lighting at time of accidentMight be important for evaluation and determining countermeasures Federal Aid (Final, Primary, Secondary, Urban, Not built etc.) Functional Class (Freeway, Rural, Urban)

22. Center for Risk Management of Engineering Systems University of Virginia, Charlottesville 172 Vehicle Record ParameterExplanationSignificance Vehicle Type The type of vehicleMight be useful for evaluation and determining exposure Estimated Speed The estimated speed of the driverUseful for evaluation and determining exposure Vehicle Maneuver The control of the car at the time of the accident ( run off the road, etc.) Useful for evaluation to determine significance of guardrail Vehicle Placement Vehicle Skidding The involvement of skidding to the accident Might be useful for evaluation Fixed Object The type of fixed object involved in accident Useful for evaluation to determine significance of guardrail and exposure Tractor Length Trailer1 Length Trailer2 Length Trailer Width

23. Center for Risk Management of Engineering Systems University of Virginia, Charlottesville 173 Vehicle Record (cont.) ParameterExplanationSignificance Number Axles Vehicle Condition Defects in vehicleMight be useful for evaluation to determine trends and significance of guardrail Driver AgeAge of driver Driver SexSex of driver Driver Action The action of the driver responsible for the accident (i.e. sleeping, swerving, drinking) Might be useful for evaluation to determine significance of guardrail Driver Condition Defects of driverMight be useful for evaluation to determine significance of guardrail Driver Drinking The presence or absence of alcohol from the driver Might be useful for evaluation to determine significance of guardrail Driver Visibility The vision of the driver at the time of accident

24. Center for Risk Management of Engineering Systems University of Virginia, Charlottesville 174 Synthesis of Relevant Data on HTRIS for Screening Individual AccidentsOffset from Node Collision Type Number of Vehicles Number of Fatalities Number of Injuries Accident RecordProperty Damage Shoulder Width Severity Vehicle RecordFixed Object Vehicle maneuver

25. Center for Risk Management of Engineering Systems University of Virginia, Charlottesville 175 Limitations and Recommendations Limitations –Time consuming to search all accidents –15+ hours for New Kent County for limited amount of data –Must examine multiple screens to obtain all relevant data Recommendations –Search database without limiting search to nodes –Enter search parameters of interest and receive a report