Safety

1. 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. 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. Investigating Risk • Conditions of exposure • Identify the adverse effect • Relate exposure with risk • Estimate overall risk (Lowrance, 1976)

4. 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. 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. 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. 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. 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. Accident Statistics (cont.) • Advantages • Available and assessable • Factual • Public interest

10. Examination of HTRIS • Compare date gathering methodologies using HTRIS • Guide to collecting data from HTRIS • Capabilities available in HTRIS • Alternatives to HTRIS

11. 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. 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. Guide to Collecting Data Enter Road ID Press F 10 for node locator Enter HTRIS Enter ‘y’ for node list Enter County Code at “jurisdiction” prompt Is the furthest node less than five miles away from the first node? Enter ‘x’ at first node Enter ‘y’ at last node Press F 6 when done YES NO Enter ‘x’ at first node Enter ‘y’ at furthest node within five miles of first node Press F 6 when done Press F 6 to analyze all accidents Hit enter to see summary statistics Type ‘y’ to see individual accidents 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. Hit enter to see Accident Record Inquiry if more information is desired Hit enter to see Vehicle Record Inquiry if more information is required

14. Data Available from HTRIS • Summary statistics • Individual accidents • Accident Record • Vehicle Record

15. Parameter Explanation Significance 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 accidents The 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 Summary Statistics

16. Parameter Explanation Significance 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. Date The date the accident occurred Offset from Node The distance in miles from the accident to the node Useful for evaluation to compare precise locations Direction The 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. Weather The 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. Individual Accidents

17. Parameter Explanation Significance 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 Individual Accidents (cont.)

18. Parameter Explanation Significance 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 County The county the accident occurred Useful for obtaining accidents specific to a particular county Intersect Route The Intersection Route Useful for screening by providing information on the routes Offset The 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 road Useful for evaluation – may reveal the significance of guardrail Type of Collision The type of collision Redundant – information available in summary statistics Accident Record

19. Parameter Explanation Significance # vehicles The number of vehicles Redundant # killed The number of fatalities Redundant # injured The number of injuries Redundant Type of environment Date The date the accident occurred Redundant Route The route the accident occurred on Useful for screening City The city the accident occurred in Node Surface Width Surface Type The surface of the road Traffic Control The traffic control Might be useful for evaluation and determining countermeasures Severity The severity of the accident Information on the adverse effects Accident Record (cont.)

20. Parameter Explanation Significance Weather The 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 occurred Might be useful for evaluation by revealing the relevance of guardrail Time The time the accident occurred Might be useful for evaluation and determining countermeasures by revealing trends Accident Record (cont.)

21. Parameter Explanation Significance District The 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? Light The lighting at time of accident Might be important for evaluation and determining countermeasures Federal Aid (Final, Primary, Secondary, Urban, Not built etc.) Functional Class (Freeway, Rural, Urban) Accident Record (cont.)

22. Parameter Explanation Significance Vehicle Type The type of vehicle Might be useful for evaluation and determining exposure Estimated Speed The estimated speed of the driver Useful 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 Vehicle Record

23. Parameter Explanation Significance Number Axles Vehicle Condition Defects in vehicle Might be useful for evaluation to determine trends and significance of guardrail Driver Age Age of driver Driver Sex Sex 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 driver Might 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 Vehicle Record (cont.)

24. Individual Accidents Offset from Node Collision Type Number of Vehicles Number of Fatalities Number of Injuries Accident Record Property Damage Shoulder Width Severity Vehicle Record Fixed Object Vehicle maneuver Synthesis of Relevant Data on HTRIS for Screening

25. 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