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Evacuation Demand

Evacuation Demand. CE 4780 – Hurricane Engineering Spring 2003. Introduction. Evacuation – what it is and why we do it. What it is – its ‘getting out of Dodge’ Why we do it – avoid injury or death, sometimes to protect property Pre-event and post-event evacuation.

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Evacuation Demand

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  1. Evacuation Demand CE 4780 – Hurricane Engineering Spring 2003

  2. Introduction • Evacuation – what it is and why we do it. • What it is – its ‘getting out of Dodge’ • Why we do it – avoid injury or death, sometimes to protect property • Pre-event and post-event evacuation.

  3. Types of Evacuation • Pre-event evacuation: • When there is warning of an event • When negative effects are avoided by moving • When movement is possible and feasible • When information regarding the hazard and the opportunity for evacuation are adequately conveyed.

  4. Types of Evacuation • Post-event evacuation: • When conditions caused by the event are lasting and harmful • When harmful conditions can be avoided by moving away

  5. Travel Demand • Term used in transportation to describe the amount of travel generated by people. • Travel demand is expressed in terms of TRIPS and, in regular transportation planning, is expressed as the number of vehicles per day that will travel on individual links in the network. • The demand on each link determines the needed size of the link.

  6. Evacuation Demand • Is different from normal travel demand because trips are: • Less discretionary • Involves larger volumes of traffic • Timing is more important • More opportunity for intervention in travel decisions (e.g. evacuation orders, routing directives.

  7. Evacuation Demand • In normal travel demand, link volumes are important. • In evacuation demand, link volume, the time when evacuation occurs, and the location from which it takes place, is important.

  8. Example road d1 d2 d3 t1 t3 d t2 Zone 1 Zone 2 Zone 3 The load on the road network is dependent on the dynamic loading rates at each zone, the relative timing (sequencing) of the loading among zones, and the relative location of the zones. dd4

  9. Evacuation Demand • Is different from normal travel demand because the factors driving the decision to make a trip (evacuate) are different: • Normal trips are made in order to participate in an activity (work, shop, school, recreation, etc.) • Evacuation trips are made to avoid danger and are influenced by factors such as level of threat, vulnerability of the individual, imminence of threat, and opportunity to avoid danger.

  10. Evacuation Demand • Evacuation demand = f(threat level, imminence of threat, vulnerability to threat, opportunity to evade threat) • Some causal factors are static (e.g. vulnerability to threat) and others are dynamic (e.g. threat level).

  11. Why Do We Want to Estimate Evacuation Demand? • To be able to “model” evacuation travel under alternative scenarios. • With the ability to model we can: • Estimate impact of alternative policies and strategies with different storm scenarios • Identify optimum contingency plans • Estimate impact of alternative investment strategies

  12. Before we proceed into modeling, lets look at the behavioral analysis that has been conducted in the past and what has been learned.

  13. Behavioral Analysis How people have behaved during past evacuations (revealed behavior) Or How they say they would behave under alternative hypothetical situations (stated behavior)

  14. Revealed and Stated Behavior • Revealed behavior: • Requires that an event first occur • The characteristics of the event are fixed • Not all information can be gathered (e.g. speed, delay, route) • Stated behavior, on the other hand: • Can be gathered at any time • Characteristics of event are not fixed • Even less information can be gathered than in the revealed behavior case because variables describing scenarios must be limited.

  15. Revealed Behavior in the Past

  16. Past Incidence of Hurricanes on Central Gulf Coast

  17. Conclusion From Previous Slide • No location more prone to hurricanes than another, other than in a regional sense. • While general alignment of hurricane tracks are discernible, individual tracks are unpredictable.

  18. Evacuation Rates

  19. Factors Motivating Evacuation • 1. Risk of flooding: • High risk – elevation < 10 foot above sea level • Moderate risk – elevation 10-15 feet above sea level • Low risk – elevation > 15 feet above sea level • Evacuation rates in high risk areas are often 3 times those in low risk areas. • People in low risk areas may not need to evacuate at all – those that do are shadow evacuees.

  20. Factors Motivating Evacuation • 2. Evacuation Orders: • Precautionary or voluntary evacuation order • Recommended evacuation • Mandatory evacuation • Dependent on means of dissemination • Of those who hear a mandatory evacuation order, over 80% have evacuated in the past. • Of those who do not hear, less than 20% have evacuated in the past

  21. Factors Motivating Evacuation • 3. Housing: • Mobile home dwellers are more likely to evacuate than persons in other home types. • People in high-rise buildings are less likely to evacuate than those in regular houses, all else being equal.

  22. Factors Motivating Evacuation • 4. Storm Threat Information: • The National Hurricane Center issues storm advisories (storm watches and storm warnings). • Storm watches are issued when a storm is expected to make landfall within 36 hours. • Storm warnings are issued when a storm is expected to make landfall within 24 hours.

  23. Factors Motivating Evacuation • 5. Storm severity: • High correlation with evacuation orders and flooding. • Few studies have been conducted following weak storms, so information on low storm severity is sparse.

  24. Factors Influencing Decision to not Evacuate • Protect property from storm • Protect property from looters • Fulfill obligation to employer • Sometimes, peer pressure from neighbors • < 5% said they did not have transportation

  25. Louisiana-Mississippi 2002 Hurricane Behavioral Response Survey Telephone survey Jan-Feb 2002 Earl J. Baker presentation to S.E. Louisiana officials, 2002

  26. Sample DesignLouisiana • Orleans Parish N=400 • Jefferson Parish N=400 • SE Louisiana N=400 • St. Tammany So. of I-10/I-12 N=134 • St. Bernard N=133 • Plaquemines N=133 Earl J. Baker presentation to S.E. Louisiana officials, 2002

  27. Sample DesignMississippi Earl J. Baker presentation to S.E. Louisiana officials, 2002

  28. Evacuation RatesGeorges and Hypotheticals Earl J. Baker presentation to S.E. Louisiana officials, 2002

  29. Destinations in Georgesfrom Louisiana Earl J. Baker presentation to S.E. Louisiana officials, 2002

  30. Cat 3, So., Intended Destinations Earl J. Baker presentation to S.E. Louisiana officials, 2002

  31. Cat 3, SW, Intended Destinations Earl J. Baker presentation to S.E. Louisiana officials, 2002

  32. Cat 4, So., Intended Destinations Earl J. Baker presentation to S.E. Louisiana officials, 2002

  33. Cat 4, SW, Intended Destinations Earl J. Baker presentation to S.E. Louisiana officials, 2002

  34. Routes in Georges Earl J. Baker presentation to S.E. Louisiana officials, 2002

  35. Cat 3, So., Intended Routes Earl J. Baker presentation to S.E. Louisiana officials, 2002

  36. Cat 3, SW, Intended Routes Earl J. Baker presentation to S.E. Louisiana officials, 2002

  37. Would Use Alternate Route if Asked by Officials Earl J. Baker presentation to S.E. Louisiana officials, 2002

  38. Would Avoid Interstates if Asked by Officials Earl J. Baker presentation to S.E. Louisiana officials, 2002

  39. Intended Use if I-10, I-55 One-Way Earl J. Baker presentation to S.E. Louisiana officials, 2002

  40. Intended Use if I-10, I-59 One-Way Earl J. Baker presentation to S.E. Louisiana officials, 2002

  41. Intended Use if I-10, I-49 One-Way Earl J. Baker presentation to S.E. Louisiana officials, 2002

  42. Intended Use if I-55 One Way Earl J. Baker presentation to S.E. Louisiana officials, 2002

  43. Intended Use if I-59 One Way Earl J. Baker presentation to S.E. Louisiana officials, 2002

  44. Effect on One-Way Flow on Decision to Evacuate Earl J. Baker presentation to S.E. Louisiana officials, 2002

  45. Concerned About Being Trapped in Traffic in Georges Earl J. Baker presentation to S.E. Louisiana officials, 2002

  46. Heard Evacuation Information While on the Road in Georges Earl J. Baker presentation to S.E. Louisiana officials, 2002

  47. Type of Refuge Used in Georges Earl J. Baker presentation to S.E. Louisiana officials, 2002

  48. Type of Refuge Intended in Cat 3, So. Earl J. Baker presentation to S.E. Louisiana officials, 2002

  49. Effect of Hearing That Shelters, Lodging Are Full Before Evacuating Earl J. Baker presentation to S.E. Louisiana officials, 2002

  50. Effect of Hearing That Roads Are Heavily Congested Before Evacuating Earl J. Baker presentation to S.E. Louisiana officials, 2002

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