《数学建模》美赛优秀论文：2001b with Floyd A Traffic Flow Analysis of South Carolina Hurricane Evacuation.pdf_大学文库

302 The UMAP Journal 22.3 (2001) Level of Service E represents operating conditions at or near capacity level. All speeds are reduced to a low but relatively uniform value, normally between 30 and 46 mpl Level of Service F is used to define forced or breakdown flow, with speeds of less than 30 mph. This condition exists wherever the amount of traffic approaching a point exceeds the amount that can traverse that point. Queues form behind such locations If we enter LOS F, the roadway has exceeded its capacity and the usefulness of the evacuation has broken down. An evacuation strategy that results in a highway reaching LOS F is unacceptable For a given highway, we can determine the maximum number of vehicles that can flow through a particular section while maintaining a desired level of service. To make this more concrete, we define the characteristic quantity iaxIImlIn service flow Definition. Maximum Service Flow(MSFi) for agivenlevel of service i, assuming ideal roadway conditions, is the maximum possible rate of flow for a peak 15- min period, expanded to an hourly volume and expressed in passenger cars per hour per lane(pcphpl). To calculate the msF of a highway for a given LOS,we multiply the roads capacity under ideal conditions by the volume-to-capacity ratio for the desired LOS. More formally, MSFi=ci=, where c, is the capacity under ideal conditions for a freeway with Design Speed j, and (o/c)i is the maximum volume-to-capacity ratio associated with LOS i. For highways with 60-and 70-mph design speeds, c; is 2,000 pcphpl [Transportation Research Board 1985]. Since LOS E is considered to be"at capacity, "(U/cE=1.0. The design speed of a road is based mostly on the importance and grade of the road; roads that are major and have shallower grades have higher design speeds. The elevation profile along I-26 shows that South Carolina is flat enough to warrant the highest design speed An immediate consequence of (1)is that to maintain MSFe or better(which we consider necessary for a successful evacuation), the number of passenger cars per hour per lane must not exceed 2,000 for any highway. For it to be useful in model calculations, we need to convert the maximum service flow to a quantity that conveys information about a particular roadway This quantity is known as the service flow rate of a roadway. Definition. The service flow rate for level of service i, denoted SFi, is the actual maximal flow that can be achieved given a roadway and its unique set of prevailing conditions. The service flow rate is calculated SFi= MSFi Nfo fHv fp in terms of the adjustment factors

302 The UMAP Journal 22.3 (2001) • Level of Service E represents operating conditions at or near capacity level. All speeds are reduced to a low but relatively uniform value, normally between 30 and 46 mph. • Level of Service F is used to define forced or breakdown flow, with speeds of less than 30 mph. This condition exists wherever the amount of traffic approaching a point exceeds the amount that can traverse that point. Queues form behind such locations. If we enter LOS F, the roadway has exceeded its capacity and the usefulness of the evacuation has broken down. An evacuation strategy that results in a highway reaching LOS F is unacceptable. For a given highway, we can determine the maximum number of vehicles that can flow through a particular section while maintaining a desired level of service. To make this more concrete, we define the characteristic quantity maximum service flow. Definition. Maximum Service Flow(MSFi) for a given level of service i, assuming ideal roadway conditions, is the maximum possible rate of flow for a peak 15- min period, expanded to an hourly volume and expressed in passenger cars per hour per lane (pcphpl). To calculate the MSF of a highway for a given LOS, we multiply the roadís capacity under ideal conditions by the volume-to-capacity ratio for the desired LOS. More formally, MSFi = cj v c i , (1) where cj is the capacity under ideal conditions for a freeway with Design Speed j, and (v/c)i is the maximum volume-to-capacity ratio associated with LOS i. For highways with 60- and 70-mph design speeds, cj is 2,000 pcphpl [Transportation Research Board 1985]. Since LOS E is considered to be ìat capacity,î (v/c)E = 1.0. The design speed of a road is based mostly on the importance and grade of the road; roads that are major and have shallower grades have higher design speeds. The elevation profile along I-26 shows that South Carolina is flat enough to warrant the highest design speed. An immediate consequence of (1) is that to maintain MSFE or better (which we consider necessary for a successful evacuation), the number of passenger cars per hour per lane must not exceed 2,000 for any highway. For it to be useful in model calculations, we need to convert the maximum service flow to a quantity that conveys information about a particular roadway. This quantity is known as the service flow rate of a roadway. Definition. The service flow rate for level of service i, denoted SFi, is the actual maximal flow that can be achieved given a roadway and its unique set of prevailing conditions. The service flow rate is calculated as SFi = MSFiNfwfHVfp, (2) in terms of the adjustment factors:

Jammin with Floyd 303 N: the number of lanes fu: the adjustment for nonideal lane widths and lateral clearances, fHv: effect of nonpassenger vehicles, and fp: the adjustment for nonideal driver populations We assume that the lanes on I-26 and other high wavs are l deal (i.e. fu=1):at least 12 ft wide with obstructions at least 6 ft from traveled pavement [Manner- ing and Kilareski 1990]. To account for driver unfamiliarity with reversed lanes and stress of evacuation, we set fp=0.7 for reversed lanes and fp =0.8 for normal lanes, in accordance with Mannering and Kilareski [ 1990]. The model also employs an adjustment factor, denoted fHv, for reduction of flow due to heavy vehicles such as trucks, buses, RVs, and trailers. Later we discuss the effects of heavy vehicles on traffic flow. Strengths and Weaknesses This model is easy to implement, the mathematics behind it is quite sim ple, and it is backed by the National Transportation Board. We establish its reliability by using it to predict traffic flow patterns in the 1999 evacuation We assume that the number of lanes does not change, which requires that here are no lane restrictions throughout the length of the freeway and no lanes are added or taken away by construction. The major weakness of our model is that it fails to take into account the erratic behavior of people under the strain of a natural disaster. The simplicity of our model also limits its usefulness. It can be applied only to normal highway situations, not to a network of roads Improving Evacuation Flow Gathering data from a various sources, we estimate the number of vehi cles used in the 1999 evacuation. According to Dow and Cutter [2000, 65% of households that were surveyed chose to evacuate. About 70% of households used one vehicle or fewer, leaving 30% of households taking two vehicles. Of the evacuees, 25% used 1-26 during the evacuation. Based on population esti- mates[County Population Estimates.. 1999] and average number of people per household [Estimates of Housing Units . 19981, and assuming a rela- tively uniform distribution of people per household, we calculate the number of vehicles used during the evacuation (Table 1)

Jamminí with Floyd 303 N: the number of lanes, fw: the adjustment for nonideal lane widths and lateral clearances, fHV: effect of nonpassenger vehicles, and fp: the adjustment for nonideal driver populations. We assume that the lanes on I-26 and other highways are ideal (i.e., fw = 1): at least 12 ft wide with obstructions at least 6 ft from traveled pavement [Mannering and Kilareski 1990]. To account for driver unfamiliarity with reversed lanes and stress of evacuation, we set fp = 0.7 for reversed lanes and fp = 0.8 for normal lanes, in accordance with Mannering and Kilareski [1990]. The model also employs an adjustment factor, denoted fHV, for reduction of flow due to heavy vehicles such as trucks, buses, RVs, and trailers. Later we discuss the effects of heavy vehicles on traffic flow. Strengths and Weaknesses This model is easy to implement, the mathematics behind it is quite simple, and it is backed by the National Transportation Board. We establish its reliability by using it to predict traffic flow patterns in the 1999 evacuation. We assume that the number of lanes does not change, which requires that there are no lane restrictions throughout the length of the freeway and no lanes are added or taken away by construction. The major weakness of our model is that it fails to take into account the erratic behavior of people under the strain of a natural disaster. The simplicity of our model also limits its usefulness. It can be applied only to normal highway situations, not to a network of roads. Improving Evacuation Flow Gathering data from a various sources, we estimate the number of vehicles used in the 1999 evacuation. According to Dow and Cutter [2000], 65% of households that were surveyed chose to evacuate. About 70% of households used one vehicle or fewer, leaving 30% of households taking two vehicles. Of the evacuees, 25% used I-26 during the evacuation. Based on population estimates [County Population Estimates ... 1999] and average number of people per household [Estimates of Housing Units ... 1998], and assuming a relatively uniform distribution of people per household, we calculate the number of vehicles used during the evacuation (Table 1)

304 The UMAP Journal 22.3 (2001) Table 1. Evacuation participation estimates for Hurricane Floyd, in thousands. Population Evacuees Evacuating Vehicles Vehicles Households on I-26 Southern 187 122 47 61 ó Central 553 359 139 181 ó Northern 233 152 59 76 ó Total 973 632 245 319 61 Reversing Lanes According to our model, the capacity of a highway is directly proportional to the number of lanes. This implies that lane reversal would nearly double the capacity of I-26. Approximately 319,000 vehicles were used to evacuate the coastal counties of South Carolina. Of evacuees surveyed by Dow and Cutter [2000], 16.3% evacuated between noon and 3 p.m. on Sept. 14. Assuming independence between the above factors, in the hours between 9 a.m. and noon, I-26 must have been clogged by an attempted influx of about 3,300 vehicles/h. Even if evenly distributed, this was more than the 3,200 vehicles/h that the two Columbia-bound lanes of I-26 could take under evacuation conditions. The result was LOS Fóa large traffic jam. Our model predicts that this jam would have lingered for hours, even after the influx of vehicles had died down. What if the coastal-bound lanes of I-26 were reversed? With corrections for nonideal conditions, our model predicts an SFE of 6,000 pcphpl. Therefore, reversing the lanes of I-26 has the potential to increase service flow rate by a factor of 1.6. Simultaneous Evacuation Strategies By Hurricane Path Hurricanes sweep from south to north. Because a hurricane commonly travels at a speed of less than 30 mph, the southernmost counties of South Carolina would be affected at least two hours before the northernmost ones. However, analysis indicates that a staggered evacuation strategy would not improve the speed of the evacuation. The evacuation routes are largely parallel to one another and rarely intersect. Thus, the evacuation of each county should affect only the traffic on evacuation routes of nearby counties. Therefore, postponing evacuation of counties farther from the hurricane would be counterproductive

306 The UMAP Journal 22.3 (2001) Lane reversal on Smaller highways As only 29% of evacuees took 1-26 or I-95, the majority took smaller road inland. Because our model results in linear growth of flow with number of available lanes, lane reversals should improve evacuation rates on all roads Because the evacuation routes are nearly perpendicular to the coastline, there is little risk of opposing traffic being disrupted by these reversals. The logistics of such an action, however, might be prohibitive The number of personnel needed to facilitate the 1-26 lane reversal is 206 [South Carolina Emergency Preparedness Division 2000]. Smaller highways have less distance between exits, which suggests that more personnel per mile would be needed to blockade highway entrances. The total length of highway on all evacuation routes is approximately ten times as great as the length of I-26. Therefore, a truly prodigious amount of human effort would be necessary to implement lane reversals on all evacuation routes It would be imprudent to spend resources for what we estimate to be only a marginal gain in actual highway use. According to Dow and Cutter [20001, these alternative routes did not even approach capacity during the last evacua- tion. Since our license-plate evacuation strategy increases the overall through put of major evacuation routes through lane reversal and smoother time distri bution, there is no reason to expect a heavier load on state and country roads o, there is little evidence to support the utility of lane reversal on all smaller roads. Still, reversing lanes on a small numberof evacuation routes might prove useful. The three major population centers of the coast(Beaufort, Charleston, and Horry counties) have different evacuee distributions. Therefore, those highways which most meritreversal are I-26, I-501 from Myrtle Beach to Marion and 301 from marion to florence and the southern corridor from beaufort County to the augusta area Effect of Additional Temporary Shelters In 1999, South Carolina housed about 325,000 people in shelters [Dow an Cutter 2000]. In a hurricane, one-third of evacuees go to each of shelters, family and friends, and commercial establishments [Zelinski and Kosinski 1991, 39- 44]. According to South Carolina Hurricane Information [2001, the number of predesignated shelters in Columbia is insignificant. However, there must be an efficient way to funnel the evacuees to the evacuation sites, such as a central coordination center with an up-to-date list of where the next group of cars should go Vehicle Type restrictions Although our model generally calculates flow using only normal passenger cars, it is not difficult to take other types of vehicles into account. The equation

306 The UMAP Journal 22.3 (2001) Lane Reversal on Smaller Highways As only 29% of evacuees took I-26 or I-95, the majority took smaller roads inland. Because our model results in linear growth of flow with number of available lanes, lane reversals should improve evacuation rates on all roads. Because the evacuation routes are nearly perpendicular to the coastline, there is little risk of opposing traffic being disrupted by these reversals. The logistics of such an action, however, might be prohibitive. The number of personnel needed to facilitate the I-26 lane reversal is 206 [South Carolina Emergency Preparedness Division 2000]. Smaller highways have less distance between exits, which suggests that more personnel per mile would be needed to blockade highway entrances. The total length of highway on all evacuation routes is approximately ten times as great as the length of I-26. Therefore, a truly prodigious amount of human effort would be necessary to implement lane reversals on all evacuation routes. It would be imprudent to spend resources for what we estimate to be only a marginal gain in actual highway use. According to Dow and Cutter [2000], these alternative routes did not even approach capacity during the last evacuation. Since our license-plate evacuation strategy increases the overall throughput of major evacuation routes through lane reversal and smoother time distribution, there is no reason to expect a heavier load on state and country roads. So, there is little evidence to support the utility of lane reversal on all smaller roads. Still, reversing lanes on a small number of evacuation routes might prove useful. The three major population centers of the coast (Beaufort, Charleston, and Horry counties) have different evacuee distributions. Therefore, those highways which most merit reversal are I-26, I-501 from Myrtle Beach to Marion and 301 from Marion to Florence, and the southern corridor from Beaufort County to the Augusta area. Effect of Additional Temporary Shelters In 1999, South Carolina housed about 325,000 people in shelters [Dow and Cutter 2000]. In a hurricane, one-third of evacuees go to each of shelters, family and friends, and commercial establishments [Zelinski and Kosinski 1991, 39ñ 44]. According to South Carolina Hurricane Information [2001], the number of predesignated shelters in Columbia is insignificant. However, there must be an efficient way to funnel the evacuees to the evacuation sites, such as a central coordination center with an up-to-date list of where the next group of cars should go. Vehicle Type Restrictions Although our model generally calculates flow using only normal passenger cars, it is not difficult to take other types of vehicles into account. The equation

Jammin with Floyd 307 used to calculate the heavy-vehicle adjustment factor is V (3) 1+0.6P where P is the proportion of nonpassenger vehicles(Rvs, trailers, and boats) Using this equation, our model predicts an upper bound on the proportion of nonpassenger vehicles that occur without causing LOS F We demonstrate this with a sample calculation using 1-26. Earlier, we estimated the SFe of I-26 including reversed lanes, as 6,000 pcphpl. We also estimated that a maximum of 3, 300 vehicles /h would enter I-26, ignoring the possibility of spikes in activity Therefore, the minimum safe value of fHv is approximately 0.55, which means that 1-26 has enough leeway to support any mix of passenger cars and heavy vehicles. There is no need to restrict large vehicles on I-26 Georgians, Floridians, and the 1-95 Corridor According to Georgias hurricane evacuation plan Hurricane Evacuation Routes 2001, I-95 is not a valid evacuation route. However, thousands of Floridians and Georgians flocked north on 1-95 during Hurricane Floyd. In Savannah, the most popular evacuation route was 1-16, which goes directly away from South Carolina [Officials deserve high marks.. 1999]. In South Carolina, as shown in Figures 1 and 2, the farther away the destination, the smaller the percentage of the evacuee population that plans to go there. Takin all this into account, a realistic upper bound for the percentage of Georgians or Floridians using I-95 is 20%0 Any population entering South Carolina on I-95 from Georgia or Florida mostly bound for major cities; an upper bound on the traffic headed through Columbia would be 75%. Since Floyd's landfall was extraordinarily unpre- dictable, we propose that it was one of the largest evacuations that will affect South carolina Our reasoning is as follows: Hurricanes of lesser strength have fewer evac. uees. If the landfall of the hurricane is more southerly there is less need to evacuate South Carolina and North Carolina and so there will be less traffic on the I-26. Lastly, if the hurricane tends more towards the north, the number of evacuee drivers from Georgia and Florida taing I-95 will be decreased greatl So, we can take floyd as a relative upper bound on evacuees From CNN's coverage of the lead up to Hurricane Floyd's landfall, in Geor gia, we know that"the evacuation orders affected 500,000 people. "We bound this rough estimate by 600,000. So the upper bound of people using I-95 can be estimated as(0.20)(0.75)(600,000)a 90,000, or about 45,000 vehicles, spread over a two-day period From Dow and Cutter [2000 we know that about 10% of South Carolina evacuees used I-95, so the georgians and Floridians effec- tively doubled the traffic on I-95, which is a huge impact on the model that we have proposed

Jamminí with Floyd 307 used to calculate the heavy-vehicle adjustment factor is fHV = 1 1+0.6P , (3) where P is the proportion of nonpassenger vehicles (RVs, trailers, and boats). Using this equation, our model predicts an upper bound on the proportion of nonpassenger vehicles that occur without causing LOS F. We demonstrate this with a sample calculation using I-26. Earlier, we estimated the SFE of I-26, including reversed lanes, as 6,000 pcphpl. We also estimated that a maximum of 3,300 vehicles/h would enter I-26, ignoring the possibility of spikes in activity. Therefore, the minimum safe value of fHV is approximately 0.55, which means that I-26 has enough leeway to support any mix of passenger cars and heavy vehicles. There is no need to restrict large vehicles on I-26. Georgians, Floridians, and the I-95 Corridor According to Georgiaís hurricane evacuation plan [Hurricane Evacuation Routes 2001], I-95 is not a valid evacuation route. However, thousands of Floridians and Georgians flocked north on I-95 during Hurricane Floyd. In Savannah, the most popular evacuation route was I-16, which goes directly away from South Carolina [Officials deserve high marks ... 1999]. In South Carolina, as shown in Figures 1 and 2, the farther away the destination, the smaller the percentage of the evacuee population that plans to go there. Taking all this into account, a realistic upper bound for the percentage of Georgians or Floridians using I-95 is 20%. Any population entering South Carolina on I-95 from Georgia or Florida is mostly bound for major cities; an upper bound on the traffic headed through Columbia would be 75%. Since Floydís landfall was extraordinarily unpredictable, we propose that it was one of the largest evacuations that will affect South Carolina. Our reasoning is as follows: Hurricanes of lesser strength have fewer evacuees. If the landfall of the hurricane is more southerly, there is less need to evacuate South Carolina and North Carolina and so there will be less traffic on the I-26. Lastly, if the hurricane tends more towards the north, the number of evacuee drivers from Georgia and Florida taing I-95 will be decreased greatly. So, we can take Floyd as a relative upper bound on evacuees. From CNNís coverage of the lead up to Hurricane Floydís landfall, in Georgia, we know that ìthe evacuation orders affected 500,000 people.î We bound this rough estimate by 600,000. So the upper bound of people using I-95 can be estimated as (0.20)(0.75)(600,000) ≈ 90,000, or about 45,000 vehicles, spread over a two-day period. From Dow and Cutter [2000], we know that about 10% of South Carolina evacuees used I-95, so the Georgians and Floridians effectively doubled the traffic on I-95, which is a huge impact on the model that we have proposed

308 The UMAP Journal 22.3 (2001) Improvements in the model Our model needs additional evacuation data. With precise statistics regard ing number of evacuees, routes taken, time distributions, and traffic conditions, we could apply it to a greater variety of situations Additional refinements might be made to the parameters of the model with information on the highways themselves. The lane widths and distances to roadside obstacles affect the service flow rate, and knowing the exact layout of the highways would enable us to take them into account We could also use information regarding the resources available to the state how many personnel and vehicles would be available to run lane reversals With sufficient information we could use this model to create a simulation of a hurricane evacuation. We would treat the highways of South Carolina as edges in a network flow problem and run a discrete computer simulation to test our premises and conclusions regarding evacuation policies References CountyPopulationEstimatesforjUly1,1999.1999.http://www.census.gov/ population/estimates/county/co-99-1/99C1_45.txt ow,K, and S.L. Cutter. 2000. South Carolina's Response to Hurricane Floyd Quick Response Report 128. Columbia, SC: University of South Carolina http://www.coloradoedu/hazards/qr/qr128/qr128.html Estimates of Housing Units, Households, Households by Age of Householder, andPersonsperhoUsehold:July1,1998.1999.http://www.census.gov/ population/estimates/housing/sthuhh1txt FloydbashesBahamastakesaimatFlorida.1999.http://www.cnn.com, WEATHER/9909/14/floyd O7/ Gartner, Nathan, Carroll J. Messer, and Ajay K Rathi. 1992. Traffic Flow Theory A State of the Art Report. Revised monograph. Special Report 165. Oak RidgeTn:OakRidgeNationalLaboratoryhttp://www.tfhrc.gov/its/ tft/tft. htm HurricaneEvacuationRoutes-textForm.2001.http://www.georgia-navigator com/hurricane/textroutes html Mannering, F, and w. Kilareski. 1990. Principles of highway Engineering and Traffic Analysis. New York: Wiley Number of Households in South Carolina by County: 1950-1990 and Projected 1995.1996.http://www.sciway.net/statistics/scsa96/hou/hou13 html Officials deserve high marks for handling of Hurricane Floyd threat. 1999 http://www.onlineathens.com/stories/091999/ope_0919990026.shtm1

308 The UMAP Journal 22.3 (2001) Improvements in the Model Our model needs additional evacuation data. With precise statistics regarding number of evacuees, routes taken, time distributions, and traffic conditions, we could apply it to a greater variety of situations. Additional refinements might be made to the parameters of the model with information on the highways themselves. The lane widths and distances to roadside obstacles affect the service flow rate, and knowing the exact layout of the highways would enable us to take them into account. We could also use information regarding the resources available to the state: how many personnel and vehicles would be available to run lane reversals. With sufficient information, we could use this model to create a simulation of a hurricane evacuation. We would treat the highways of South Carolina as edges in a network flow problem and run a discrete computer simulation to test our premises and conclusions regarding evacuation policies. References County Population Estimates for July 1, 1999. 1999. http://www.census.gov/ population/estimates/county/co-99-1/99C1_45.txt . Dow, K., and S.L. Cutter. 2000. South Carolinaís Response to Hurricane Floyd. Quick Response Report 128. Columbia, SC: University of South Carolina. http://www.colorado.edu/hazards/qr/qr128/qr128.html . Estimates of Housing Units, Households, Households by Age of Householder, and Persons per Household: July 1, 1998. 1999. http://www.census.gov/ population/estimates/housing/sthuhh1.txt . Floyd bashes Bahamas, takes aim at Florida. 1999. http://www.cnn.com/ WEATHER/9909/14/floyd.07/ . Gartner, Nathan, Carroll J. Messer, and Ajay K. Rathi. 1992. Traffic Flow Theory: A State of the Art Report. Revised monograph. Special Report 165. Oak Ridge, TN: Oak Ridge National Laboratory. http://www.tfhrc.gov/its/ tft/tft.htm . Hurricane Evacuation RoutesóText Form. 2001. http://www.georgia-navigator. com/hurricane/textroutes.html . Mannering, F., and W. Kilareski. 1990. Principles of Highway Engineering and Traffic Analysis. New York: Wiley. Number of Households in South Carolina by County: 1950ñ1990 and Projected 1995. 1996. http://www.sciway.net/statistics/scsa96/hou/hou13. html . Officials deserve high marks for handling of Hurricane Floyd threat. 1999. http://www.onlineathens.com/stories/091999/ope_0919990026.shtml

Jammin’ vith Floyd309 PublicRoads1999.http://www.tfhrc.gov/pubrds/janfeb99/traffic.htm South Carolina Emergency Preparedness Division. 2000. Traffic Management Central Coastal Conglomerate Annex 1-26 Lane Reversal Operation Plan Formerlyavailableathttp://www.state.Sc.us/epd/hurricaneplan, ccci26rev.pdf;nowathttp://www.cs.hmc.edu/"matt/ccc.pdf SouthCarolinahurricaneEvacuationRoutes2001.http://www.dot.state scusgetting/evacuationmap pd South Carolina Hurricane Information. 2000 http://www.scan21.com/selectcounty.html SouthCarolinaPopulationDensity.1999.http://www.callsouthcarolina com/Maps/Map-Pop_ Density. htm Total Number of Housing Units by County: 1970, 1980 and 1990. 1999 http://www.ors.state.Sc.us/abstract-99/chap12/hou3.htm Transportation Research Board. 1985. Highway Capacity Manual. Special Report irginiaHurricaneEvacuationRoutes1991.http://www.vdot.state.va us/traf/hurricane. html Zelinsky, Wilbur, and Leszek A. Kosinski. 1991. The Emergency evacuation of Cities: A Cross-National Historical and Geographical Study. Savage, MD Rowman and littlefield Maurice knocks on door no one home COLUMBIA, SC(AP)Hurri- The RAD Corporations team of cane season has come with a fury here world-class hurricane experts and top- to South Carolina, where Hurricane notch traffic engineers analyzed the Maurice, the 13th named storm of the situation and developed a new evacu- season, bears down on Charleston this ation plan. "The basic idea of the plan evening. A record 80% of the popula- stems from simple math, " explained tion has been evacuated through the dr. K. Esner, director of rad Mod new evacuation plan eling. Two sets of two lanes almost When Hurricane Floyd narrowly doubles the evacuation rate missed South Carolina in 1999, the When asked to explain further, lack of preparedness for an evacuation Dr. Esner continued, On I-26, where of such a magnitude was highly evi- there was a colossal traffic jam in 1999, dent. The state government asked the we decided to reverse the flow of the Research All Day Corporation(RAd coastal-bound lanes at the first deci- Corp )to come up with a new evacu- sion of a mandatory evacuation. In ation plan that would help the coastal this way, people leaving Charleston, residents escape the ferocity of a simi- the most populous city in South Car lar sto rm olina, could take either the normal two

Jamminí with Floyd 309 Public Roads. 1999. http://www.tfhrc.gov/pubrds/janfeb99/traffic.htm . South Carolina Emergency Preparedness Division. 2000. Traffic Management Central Coastal Conglomerate Annex I-26 Lane Reversal Operation Plan. Formerly available at http://www.state.sc.us/epd/hurricaneplan/ ccci26rev.pdf ; now at http://www.cs.hmc.edu/~matt/ccc.pdf . South Carolina Hurricane Evacuation Routes. 2001. http://www.dot.state. sc.us/getting/evacuationmap.pdf . South Carolina Hurricane Information. 2000. http://www.scan21.com/selectcounty.html . South Carolina Population Density. 1999. http://www.callsouthcarolina. com/Maps/Map-Pop_Density.htm . Total Number of Housing Units by County: 1970, 1980 and 1990. 1999. http://www.ors.state.sc.us/abstract_99/chap12/hou3.htm . Transportation Research Board. 1985. Highway Capacity Manual. Special Report 209. Virginia Hurricane Evacuation Routes. 1991. http://www.vdot.state.va. us/traf/hurricane.html . Zelinsky, Wilbur, and Leszek A. Kosinski. 1991. The Emergency Evacuation of Cities: A Cross-National Historical and Geographical Study. Savage, MD: Rowman and Littlefield. Maurice Knocks on Door, No One Home Columbia, S.C. (AP)ó Hurricane season has come with a fury here to South Carolina, where Hurricane Maurice, the 13th named storm of the season, bears down on Charleston this evening. A record 80% of the population has been evacuated through the new evacuation plan. When Hurricane Floyd narrowly missed South Carolina in 1999, the lack of preparedness for an evacuation of such a magnitude was highly evident. The state government asked the Research All Day Corporation (RAD Corp.) to come up with a new evacuation plan that would help the coastal residents escape the ferocity of a similar storm. The RAD Corporationís team of world-class hurricane experts and topnotch traffic engineers analyzed the situation and developed a new evacuation plan. ìThe basic idea of the plan stems from simple math,î explained Dr. K. Esner, Director of RAD Modeling. ìTwo sets of two lanes almost doubles the evacuation rate.î When asked to explain further, Dr. Esner continued, ìOn I-26, where there was a colossal traffic jam in 1999, we decided to reverse the flow of the coastal-bound lanes at the first decision of a mandatory evacuation.î In this way, people leaving Charleston, the most populous city in South Carolina, could take either the normal two

310 The umaP Journal 22.3(2001) lanes of 1-26 or the two"contra-flow ically or basically divide the popu- (reversed)lanes of 1-26 all the way to lation right down the middle, using Columbia even/odd lie cense olate numbers p The evacuees in the many With the proposed RAD plan, peo- Columbia shelters seemed in good ple with even license plates left in the spirits. There was much less traffic- first group, right when the evacua- related annoyance than was felt in tion order was given, and people with 1999. John C. Lately, a British resident odd license plates or vanity plates left of Myrtle Beach, joked, "You realize starting 6 hours later. I thought the that in England, driving on the left is plan was crazy, "remarked Charles Or commonplace; I felt right at home. ange, a 24-year-old Charleston resi There was nothing but praise for dent. "They told us to evacuate by li- the RAD engineers. "A remarkable cense plate number; you'd never think difference was seen between the chaos high school math would help you one of evacuating for hurricane Floyd day, but this is one time it did! "he in 1999 and the evacuation today, " exclaimed said Joseph P. Riley, Jr, mayor of Using the 1999 data, the RAd re- Charleston. " This time the drive be- searchers calculated that breaking the tween Charleston and Columbia took evacuating population into two equal 4 hours instead of 18. And it's a good groups and delaying one group by 6 thing, too; this time the storm didn't hours led to a condition where the vol ume of cars at no time exceeded the Another feature of the new evacua- maximum volume that the road could tion plan was the breakup of the evac- handle. In this way, there was no prob- uating public into two groups. One lem with traffic jams, and Charleston of our concerns about the 1999 Floyd became a ghost town, safe for Maurice evacuation was the volume of cars all to make its appearance trying to access the emergency roads The majority of the people left on at the same time, " explained Dr Esner. the beaches are surfers and media, but He continued, "To alleviate the traffic even they are sparse in number; all volume pressure, we wanted to divide that remains is a hurricane without an the population into two groups. We audience had two different proposals; we could Hurricane Maurice could not be break up the population geograph- reached for comment Christopher Hanusa, Ari Nieh, Matthew Schnaider, in Claremont, Calif

310 The UMAP Journal 22.3 (2001) lanes of I-26 or the two ìcontra-flowî (reversed) lanes of I-26 all the way to Columbia. The evacuees in the many Columbia shelters seemed in good spirits. There was much less trafficrelated annoyance than was felt in 1999. John C. Lately, a British resident of Myrtle Beach, joked, ìYou realize that in England, driving on the left is commonplace; I felt right at home.î There was nothing but praise for the RAD engineers. ìA remarkable difference was seen between the chaos of evacuating for hurricane Floyd in 1999 and the evacuation today,î said Joseph P. Riley, Jr., mayor of Charleston. ìThis time, the drive between Charleston and Columbia took 4 hours instead of 18. And itís a good thing, too; this time the storm didnít miss.î Another feature of the new evacuation plan was the breakup of the evacuating public into two groups. ìOne of our concerns about the 1999 Floyd evacuation was the volume of cars all trying to access the emergency roads at the same time,î explained Dr. Esner. He continued, ìTo alleviate the traffic volume pressure, we wanted to divide the population into two groups. We had two different proposals; we could break up the population geographically or basically divide the population right down the middle, using even/odd license plate numbers.î With the proposed RAD plan, people with even license plates left in the first group, right when the evacuation order was given, and people with odd license plates or vanity plates left starting 6 hours later. ìI thought the plan was crazy,î remarked Charles Orange, a 24-year-old Charleston resident. ìThey told us to evacuate by license plate number; youíd never think high school math would help you one day, but this is one time it did!î he exclaimed. Using the 1999 data, the RAD researchers calculated that breaking the evacuating population into two equal groups and delaying one group by 6 hours led to a condition where the volume of cars at no time exceeded the maximum volume that the road could handle. In this way, there was no problem with traffic jams, and Charleston became a ghost town, safe for Maurice to make its appearance. The majority of the people left on the beaches are surfers and media, but even they are sparse in number; all that remains is a hurricane without an audience. Hurricane Maurice could not be reached for comment. ó Christopher Hanusa, Ari Nieh, Matthew Schnaider, in Claremont, Calif