ABSTRACT An empirical analysis was conducted to test the accuracy of imputing missing data item v... more ABSTRACT An empirical analysis was conducted to test the accuracy of imputing missing data item values in a typical travel survey using hot deck and neural network imputation procedures. The analysis was conducted on a sample of households from the 1995 Nationwide Personal Transportation Survey involving cases with no missing information. Selected data items, for which full information was available, were artificially considered as missing and hot deck and artificial neural network imputation procedures applied to impute their values. The analysis produced mixed results. Some data items were imputed with similar accuracy with the two methods while others were imputed with higher accuracy using the neural network procedure. While both procedures produced results that were unbiased and accurate at the aggregate level, accuracy at individual data item level was relatively poor with average percentage errors between the imputed and true values varying between 20 and 30 percent for the data items studied.
Different techniques are being applied for automated vehicle counting from video footage, which i... more Different techniques are being applied for automated vehicle counting from video footage, which is a significant subject of interest to many researchers. In this context, the You Only Look Once (YOLO) object detection model, which has been developed recently, has emerged as a promising tool. In terms of accuracy and flexible interval counting, the adequacy of existing research on employing the model for vehicle counting from video footage is unlikely sufficient. The present study endeavors to develop computer algorithms for automated traffic counting from pre-recorded videos using the YOLO model with flexible interval counting. The study involves the development of algorithms aimed at detecting, tracking, and counting vehicles from pre-recorded videos. The YOLO model was applied in TensorFlow API with the assistance of OpenCV. The developed algorithms implement the YOLO model for counting vehicles in two-way directions in an efficient way. The accuracy of the automated counting was ...
Abstract: Model transfer provides an alternative to undertaking complete data collection and mode... more Abstract: Model transfer provides an alternative to undertaking complete data collection and model development in every planning context. The effectiveness of the transferred model in the application context can be improved by updating selected model parameters by using ...
The use of consultants in providing pre-construction engineering design services for the state's ... more The use of consultants in providing pre-construction engineering design services for the state's Departments of Transportation has increased over the last twenty years. This has resulted in several investigations into the costeffectiveness of this trend. This paper reviews past studies, examines their methodology, suggests improvements to certain parts of the commonly-used investigative process, and demonstrates their use in an application to the Louisiana Department of Transportation and Development. The suggested improvements to methodology are described and used in this study. They include using the same project to compare in-house and consultant design costs (rather than the use of similar projects, as in most studies), performing a detailed analysis of overhead rates that are comparable between the State agency and consultants, and measuring comparative design costs as the ratio of in-house to consultant design costs (rather than the ratio of design to construction costs commonly used in past studies). Most studies in the past have concluded that consultant design costs are higher than in-house design costs or that there is no significant difference in cost. The Louisiana study found that consultants are approximately twenty percent more expensive than in-house staff in preparing road and bridge designs but that the difference was almost entirely due to the extra cost of contract preparation and in-house supervision required for consultant designs.
Transportation Research Record: Journal of the Transportation Research Board, 2016
Research into the operation of traffic flow at high volumes reveals that the capacity of freeways... more Research into the operation of traffic flow at high volumes reveals that the capacity of freeways is not a fixed number but is rather a random variable. Since traditional operational performance measures for the analysis of traffic flow on freeways typically disregard the randomness of capacity, new approaches to make use of the concept of randomness for freeway operation analysis are required. To address that need, this paper introduces a new indicator of freeway performance based solely on a stochastic approach to capacity computation. With this new indicator, the maximum reliable volume that can be carried by a freeway over prolonged time periods was derived from parameters of capacity distribution functions. The breakdown probability corresponding to the optimum volume can be used to select a single value from the capacity distribution function. To explore the empirical relationship between expected values of capacity and the optimum volumes calculated from this new computationa...
PDFTech Report06-2SSHurricanesEvacuationRoutes and routingTraffic congestionTraffic flowTransport... more PDFTech Report06-2SSHurricanesEvacuationRoutes and routingTraffic congestionTraffic flowTransportation planningData collectionSurveysRevealed preferencesTime dependenceBehaviorNew Orleans (Louisiana)Louisiana Transportation Research CenterWilmot, ChesterLouisiana Transportation Research CenterLouisiana. Dept. of Transportation and DevelopmentLouisiana State University (Baton Rouge, La.)NTL-PLANNING AND POLICY-SurveysUS Transportation CollectionCurrent hurricane evacuation transportation modeling uses an approach fashioned after thetraditional four-step procedure applied in urban transportation planning. One of the limitingfeatures of this approach is that it models traffic in a static manner. That is, link flows aremodeled as the total flow occurring on a link during an analysis period, such as a morningpeak, with no indication of the variation in traffic flow during the period. In addition, static tripassignment assumes that trips complete the journey from origin to destination during theanalysis period. During a hurricane evacuation, trips can take up to 20 hours, necessitatinglong analysis periods if static assignment is used. These two features, long analysis periodsand no indication of the variation in traffic flow during these periods, are serious limitations onthe integrity of the modeling process. Congestion is critical in estimating evacuationclearance time, evacuation efficiency, and the proportion of evacuees evacuated. Otherdifferences between ordinary day-to-day urban travel and evacuation travel include uncertaintyof road conditions, the possibility that destinations may change due to road closures or lack ofaccommodation, and the fact that an evacuation trip is mandatory rather than discretionary
016097422017PDFTech Report17-01-TA-SSConsumer preferencesEvaluationField studiesHighway safetyPas... more 016097422017PDFTech Report17-01-TA-SSConsumer preferencesEvaluationField studiesHighway safetyPassenger vehiclesPassingRural highwaysSurveysTraffic platooningTraffic speedTrucksTwo lane highwaysVariable speed limitsHighwaysMotor CarriersOperations and Traffic ManagementSafety and Human FactorsLouisianaUnited StatesLouisiana. Department of Transportation and DevelopmentDavis, HaggaiGudishala, RavindraZeringue, Kirk M.Wilmot, ChesterCodjoe, JuliusRoberts, MatthewLouisiana Transportation Research CenterLouisiana. Department of Transportation and DevelopmentNTL-OPERATIONS AND TRAFFIC CONTROLS-OPERATIONS AND TRAFFIC CONTROLSUS Transportation CollectionThis report addresses the matter of differential and uniform speed limits and their application at the state level. It was prepared in response to a request in the 2017 session of the Louisiana House of Representatives where the Louisiana Department of Transportation and Development (DOTD) was asked to \u201cstudy the safety and operational impacts of differential speed limits on interstate highways\u201d (House Concurrent Resolution 112). Thus, the purpose of this study is to inform the Louisiana Legislature about the documented various benefits and costs of a differential speed limit for passenger cars versus larger vehicles specifically with regards to the topics of Safety, Mobility and Operations, Fuel Consumption and Emissions, and Truck Determination as outlined in HCR 112. The majority of research into this topic has not been able to conclusively determine which speed limit system is safer, a uniform speed limit (USL) or a differential speed limit (DSL). There is uncertainty amongst the literature as to which is better, USL or DSL. The uncertainty is due to several factors that work against each other. Changes in observed speed are usually less than the changes in the posted speed, which dulls the impact of a DSL. If the posted speed limit is too low, many drivers will ignore it leading to low compliance rates. A slower speed reduces the severity of crashes; however, a greater speed variance increases the opportunity for crashes. Almost 75% of the nation\u2019s truck fleet cannot travel above a preset speed because they have speed limiters built in. In other countries, the limiter is mandatory, but no study has attempted to quantify the safety. In America, the current trend has states moving toward a USL. Passenger car drivers tend to prefer a DSL, but less strongly than truck drivers prefer a USL. The time and cost to fully implement a speed limit regime change can be substantial. With the lack of strong evidence in the existing published research in either direction, this paper cannot conclude which method is better than the other. Further research (on a much larger scale than this literature review) would be necessary to conclude which speed limit arrangement is better
This paper describes a number of individual-choice models of work-trip mode-choice, calibrated in... more This paper describes a number of individual-choice models of work-trip mode-choice, calibrated in the course of a bus study in two communities of Metropolitan Johannesburg. First, it is found to be useful to reduce the alternative set from eight modes to four modes, without loss of estimation power. Second, a number of alternative specifications of costs and times are examined, from which the chosen model is selected as one containing five such variables. In addition, a variable of car competition is found to add significantly to the explanatory power of the model. Finally, recently-documented procedures are applied to the selected model specification to pool the results of two random subsamples and to correct the choice-based biases in the alternative-specific constants. It is found that the coefficients of the South African model fall well within the range of coefficients determined in the U.S.
Transportation Research Part D: Transport and Environment, 2019
Extreme weather days were usually removed as outliers in past studies of taxi ridership. However,... more Extreme weather days were usually removed as outliers in past studies of taxi ridership. However, taxis play an important role during extreme weather events when other public transportation service is suspended. Thus, estimating spatio-temporal variations of taxi ridership during extreme weather conditions can provide valuable information on heretofore relatively unknown behavior of taxi riders and help identify areas with unusual taxi demands. In this study, New York City (NYC) taxi ridership shortly before the landfall of Hurricanes Irene and Sandy was analyzed. It was found that taxi ridership began to drop about 24 h before each hurricane made landfall. Six multisource regression models were estimated to explain the variation of taxi ridership in the last 24 h. Characteristics of the approaching hurricane, local weather conditions, and zonal socio-demographic variables were entered as explanatory variables. It was found that taxi ridership during hurricane-affected periods has a strong linear association with the ridership in unaffected periods but the proportion decreases as the storm approaches; a storm has the greatest impact on taxi ridership during weekend and at night, and the least impact on a weekday during the day; and taxi users make fewer trips during conditions of heavy rain or strong wind. 1. Introduction Taxi is an indispensable component of public transportation system in dense metropolitan areas such as New York City (NYC). According to data in the Census Transportation Planning Package (CTPP), commuting trips by taxi account for 2% of all commuting trips by public transportation within NYC. According to a report published by the Taxi and Limousine Commission (TLC) in 2006, NYC taxi cabs carry 11% of passengers who travel in modes of public transportation (Schaller Consulting, 2006). The most recent TLC report of 2016 states that yellow and green taxis together carry about 474,000 trips per day (NYCTLC, 2016). This statistic can be roughly validated based on data from other sources: the population of NYC is about 8.5 million, the daily person trip rate is about 2.5 trips/person for NYC residents, and about 3% of all-purpose trips use taxi or other similar shared-ride service, which gives 0.64 million taxi trips per day (PSB, 2017; U.S. Census Bureau, 2018). The significance of taxi for NYC is also revealed by the number of active taxi drivers (over 50,000) and the millions of taxi passengers they serve per year (NYCTLC, 2016). According to rules of the TLC, all licensed taxis must install the Taxicab Technology System and taxi owners must ensure this system is constantly maintained (NYCTLC, 2017). The Taxicab Technology System automatically records, collects, and transmits trip
Transportation Research Part C: Emerging Technologies, 2019
Since Hurricane Katrina, transit evacuation service has been seen to serve critical needs in affe... more Since Hurricane Katrina, transit evacuation service has been seen to serve critical needs in affected cities and an increasing number of hurricanes have struck the east coast where more people rely on public transportation to evacuate. Thus, it is important to model mode choice in evacuation for a better estimation of evacuation transit demand. In this study, a joint mode and destination type choice model was estimated based on multiple post-storm behavioral surveys from the northeastern seaboard to the Gulf coast. A Nested Logit model specification was used to estimate this joint choice model. The estimated model showed a significant linkage between mode and destination type choice, which validated the choice of a nested structure for the model. Selected variables include both household and zonal characteristics, reflecting the attributes of alternatives (e.g., hotel price and occupancy), the characteristics of households (e.g., residential stability and community density), and the interactions between them (e.g., average accessibility to a destination type). The use of multiple-storm data allowed the use of some variables that have not been considered in the past because of few variations in their values in a single dataset. Overall, the findings of this study provide insight into the factors affecting mode and destination type choice of residents during hurricane evacuation.
International Journal of Disaster Risk Reduction, 2017
In emergency evacuation there is always a need for transit for those who do not have access to pr... more In emergency evacuation there is always a need for transit for those who do not have access to private transportation or cannot walk to safety. Particularly affected among this section of society are the poor, the disabled, and the elderly. Several cities have established prepositioned pickup points to serve this section of the population but the number and location of the pickup points have usually been decided using professional judgment or based on experience from past storms. As the vulnerable section of the population typically have low mobility, getting transit pickup points close to areas of greatest need is important in order to provide better service, improve the efficiency of evacuation, and even decrease the loss of life. In this study, the spatial distribution of the population is estimated using a modified dasymetric mapping method, which estimates population distribution in terms of 30 m × 30 m land parcels. In each parcel, the vulnerable population is estimated from the proportion of disabled, aged, and zero car-owning persons in the area as determined from census data. Using Orleans parish in New Orleans as a case study and assuming a catchment area of ½ mile around each of the 17 existing pickup points, the number of vulnerable persons served by the existing system was estimated. To determine whether the 17 pickup points could be better located to serve the vulnerable optimally, the set of all eligible pickup sites were first identified and then the pickup points serving the greatest need were identified using integer linear programming. The results show that the 17 optimally located pickup points triple the vulnerable population that could be served. On the question of whether 17 is the right number of pickup points to employ, analysis shows there is a steadily decreasing average value served per pickup point as the number of pickup point increases. At some stage it would probably no longer be efficient to create additional pickup points but provide a feeder service from small demand to larger demand pickup points or link smaller demand pickup points on a route to serve several pickup points with a single service.
International Choice Modelling Conference 2017, Mar 28, 2017
In this study a joint mode and destination type choice model was developed based on evacuation be... more In this study a joint mode and destination type choice model was developed based on evacuation behavior captured in a post hurricane Irene behavior survey. A Nested Logit model specification was used with destination type being modeled in the upper nest and mode choice in the lower nest. As anticipated, the estimated model showed significant dependence between mode and destination type choice. Variables in the model included household socio-demographic characteristics, measures of social connectivity within communities, and a proxy variable of the level of transit service provided in each zone. The study provides insight into some of the factors affecting mode and destination type choice of residents during hurricane evacuation.
The objective of this study was to investigate the feasibility of using a Bluetooth Probe Detecti... more The objective of this study was to investigate the feasibility of using a Bluetooth Probe Detection System (BPDS) to estimate travel time in an urban area. Specifically, the study investigated the possibility of measuring overall congestion, the trend in congestion, the location of congestion “hotspots,” and finally measurement of the level of congestion at the hotspots using a BPDS. A secondary objective was to assess the possibility of obtaining travel time from other quicker and cheaper methods such as simply purchasing it from a commercial vendor. The findings of the study indicate that a BPDS can reliably be used to measure travel time and estimate congestion in terms of indices such as travel delay, planning time index, and travel time index. However, the acquisition of a BPDS includes certain overheads such as installation costs, maintenance costs and monitoring costs. Purchase of travel time from a commercial vendor might be a viable option if the travel time data is not nee...
This paper examines the impact of time-dependent travel cost on hurricane evacuation destination ... more This paper examines the impact of time-dependent travel cost on hurricane evacuation destination choice models based on post hurricane Floyd survey data collected in South Carolina in 1999. The network condition for destination choice model is represented by time dependent origin-destination travel cost. Multinomial logit models were applied for models with travelers evacuating to friends and relatives. The models were applied for all period, peak period and off-peak period. The results show that the dynamic model has less impact overall than the static model with static shortest path travel cost. The travelers have better knowledge of travel cost in off-peak period than in peak period and as a result, the time-dependent travel cost to the destination becomes less important in the peak period model.
The Louisiana Department of Transportation and Development (DOTD) Outsourcing Decision Assistance... more The Louisiana Department of Transportation and Development (DOTD) Outsourcing Decision Assistance Model was developed to assist officials of the DOTD to assess the outsourcing potential of individual activities or functions in the department. The model consists of both a qualitative and a quantitative assessment process which is conducted interactively by a user on a personal computer. The qualitative portion of the model uses the subjective judgment of one or more persons on a set number of perspectives, where each perspective is aimed at a different aspect of the potential for outsourcing. The quantitative portion of the model consists of the comparison of the cost of insourcing or outsourcing the activity. This manual describes how to install and use the computer program that executes both the qualitative and quantitative portions of the model.
AbstractIn this research, the factors affecting route choice in hurricane evacuation are investig... more AbstractIn this research, the factors affecting route choice in hurricane evacuation are investigated. Two hypotheses are tested. First, it is hypothesized that contrary to common practice where travel time is considered the sole or main determinant of route choice, other variables such as familiarity with the route, availability of fuel and shelter, road type, and accessibility of the route have an effect on an evacuees’ route choice as well. The second hypothesis is that as time passes and storm conditions change, the impact each variable has on route choice changes. That is, it is hypothesized that the importance evacuees assign to the factors determining route choice is not static but varies with time. The logit structure was used for modeling the choice process and stated choice data previously collected from the New Orleans area on hypothetical storms was used to calibrate the model. The study found that accessibility to a route, familiarity with the route, road type, length of a route, and availabi...
Page 1. Two dynamic travel demand models for hurricane evacuation based on survival analysis are ... more Page 1. Two dynamic travel demand models for hurricane evacuation based on survival analysis are presented: a Cox proportional hazards model and a piecewise exponential model. ... DemandModels for Hurricane Evacuation Haoqiang Fu and Chester G. Wilmot ...
ABSTRACT An empirical analysis was conducted to test the accuracy of imputing missing data item v... more ABSTRACT An empirical analysis was conducted to test the accuracy of imputing missing data item values in a typical travel survey using hot deck and neural network imputation procedures. The analysis was conducted on a sample of households from the 1995 Nationwide Personal Transportation Survey involving cases with no missing information. Selected data items, for which full information was available, were artificially considered as missing and hot deck and artificial neural network imputation procedures applied to impute their values. The analysis produced mixed results. Some data items were imputed with similar accuracy with the two methods while others were imputed with higher accuracy using the neural network procedure. While both procedures produced results that were unbiased and accurate at the aggregate level, accuracy at individual data item level was relatively poor with average percentage errors between the imputed and true values varying between 20 and 30 percent for the data items studied.
Different techniques are being applied for automated vehicle counting from video footage, which i... more Different techniques are being applied for automated vehicle counting from video footage, which is a significant subject of interest to many researchers. In this context, the You Only Look Once (YOLO) object detection model, which has been developed recently, has emerged as a promising tool. In terms of accuracy and flexible interval counting, the adequacy of existing research on employing the model for vehicle counting from video footage is unlikely sufficient. The present study endeavors to develop computer algorithms for automated traffic counting from pre-recorded videos using the YOLO model with flexible interval counting. The study involves the development of algorithms aimed at detecting, tracking, and counting vehicles from pre-recorded videos. The YOLO model was applied in TensorFlow API with the assistance of OpenCV. The developed algorithms implement the YOLO model for counting vehicles in two-way directions in an efficient way. The accuracy of the automated counting was ...
Abstract: Model transfer provides an alternative to undertaking complete data collection and mode... more Abstract: Model transfer provides an alternative to undertaking complete data collection and model development in every planning context. The effectiveness of the transferred model in the application context can be improved by updating selected model parameters by using ...
The use of consultants in providing pre-construction engineering design services for the state's ... more The use of consultants in providing pre-construction engineering design services for the state's Departments of Transportation has increased over the last twenty years. This has resulted in several investigations into the costeffectiveness of this trend. This paper reviews past studies, examines their methodology, suggests improvements to certain parts of the commonly-used investigative process, and demonstrates their use in an application to the Louisiana Department of Transportation and Development. The suggested improvements to methodology are described and used in this study. They include using the same project to compare in-house and consultant design costs (rather than the use of similar projects, as in most studies), performing a detailed analysis of overhead rates that are comparable between the State agency and consultants, and measuring comparative design costs as the ratio of in-house to consultant design costs (rather than the ratio of design to construction costs commonly used in past studies). Most studies in the past have concluded that consultant design costs are higher than in-house design costs or that there is no significant difference in cost. The Louisiana study found that consultants are approximately twenty percent more expensive than in-house staff in preparing road and bridge designs but that the difference was almost entirely due to the extra cost of contract preparation and in-house supervision required for consultant designs.
Transportation Research Record: Journal of the Transportation Research Board, 2016
Research into the operation of traffic flow at high volumes reveals that the capacity of freeways... more Research into the operation of traffic flow at high volumes reveals that the capacity of freeways is not a fixed number but is rather a random variable. Since traditional operational performance measures for the analysis of traffic flow on freeways typically disregard the randomness of capacity, new approaches to make use of the concept of randomness for freeway operation analysis are required. To address that need, this paper introduces a new indicator of freeway performance based solely on a stochastic approach to capacity computation. With this new indicator, the maximum reliable volume that can be carried by a freeway over prolonged time periods was derived from parameters of capacity distribution functions. The breakdown probability corresponding to the optimum volume can be used to select a single value from the capacity distribution function. To explore the empirical relationship between expected values of capacity and the optimum volumes calculated from this new computationa...
PDFTech Report06-2SSHurricanesEvacuationRoutes and routingTraffic congestionTraffic flowTransport... more PDFTech Report06-2SSHurricanesEvacuationRoutes and routingTraffic congestionTraffic flowTransportation planningData collectionSurveysRevealed preferencesTime dependenceBehaviorNew Orleans (Louisiana)Louisiana Transportation Research CenterWilmot, ChesterLouisiana Transportation Research CenterLouisiana. Dept. of Transportation and DevelopmentLouisiana State University (Baton Rouge, La.)NTL-PLANNING AND POLICY-SurveysUS Transportation CollectionCurrent hurricane evacuation transportation modeling uses an approach fashioned after thetraditional four-step procedure applied in urban transportation planning. One of the limitingfeatures of this approach is that it models traffic in a static manner. That is, link flows aremodeled as the total flow occurring on a link during an analysis period, such as a morningpeak, with no indication of the variation in traffic flow during the period. In addition, static tripassignment assumes that trips complete the journey from origin to destination during theanalysis period. During a hurricane evacuation, trips can take up to 20 hours, necessitatinglong analysis periods if static assignment is used. These two features, long analysis periodsand no indication of the variation in traffic flow during these periods, are serious limitations onthe integrity of the modeling process. Congestion is critical in estimating evacuationclearance time, evacuation efficiency, and the proportion of evacuees evacuated. Otherdifferences between ordinary day-to-day urban travel and evacuation travel include uncertaintyof road conditions, the possibility that destinations may change due to road closures or lack ofaccommodation, and the fact that an evacuation trip is mandatory rather than discretionary
016097422017PDFTech Report17-01-TA-SSConsumer preferencesEvaluationField studiesHighway safetyPas... more 016097422017PDFTech Report17-01-TA-SSConsumer preferencesEvaluationField studiesHighway safetyPassenger vehiclesPassingRural highwaysSurveysTraffic platooningTraffic speedTrucksTwo lane highwaysVariable speed limitsHighwaysMotor CarriersOperations and Traffic ManagementSafety and Human FactorsLouisianaUnited StatesLouisiana. Department of Transportation and DevelopmentDavis, HaggaiGudishala, RavindraZeringue, Kirk M.Wilmot, ChesterCodjoe, JuliusRoberts, MatthewLouisiana Transportation Research CenterLouisiana. Department of Transportation and DevelopmentNTL-OPERATIONS AND TRAFFIC CONTROLS-OPERATIONS AND TRAFFIC CONTROLSUS Transportation CollectionThis report addresses the matter of differential and uniform speed limits and their application at the state level. It was prepared in response to a request in the 2017 session of the Louisiana House of Representatives where the Louisiana Department of Transportation and Development (DOTD) was asked to \u201cstudy the safety and operational impacts of differential speed limits on interstate highways\u201d (House Concurrent Resolution 112). Thus, the purpose of this study is to inform the Louisiana Legislature about the documented various benefits and costs of a differential speed limit for passenger cars versus larger vehicles specifically with regards to the topics of Safety, Mobility and Operations, Fuel Consumption and Emissions, and Truck Determination as outlined in HCR 112. The majority of research into this topic has not been able to conclusively determine which speed limit system is safer, a uniform speed limit (USL) or a differential speed limit (DSL). There is uncertainty amongst the literature as to which is better, USL or DSL. The uncertainty is due to several factors that work against each other. Changes in observed speed are usually less than the changes in the posted speed, which dulls the impact of a DSL. If the posted speed limit is too low, many drivers will ignore it leading to low compliance rates. A slower speed reduces the severity of crashes; however, a greater speed variance increases the opportunity for crashes. Almost 75% of the nation\u2019s truck fleet cannot travel above a preset speed because they have speed limiters built in. In other countries, the limiter is mandatory, but no study has attempted to quantify the safety. In America, the current trend has states moving toward a USL. Passenger car drivers tend to prefer a DSL, but less strongly than truck drivers prefer a USL. The time and cost to fully implement a speed limit regime change can be substantial. With the lack of strong evidence in the existing published research in either direction, this paper cannot conclude which method is better than the other. Further research (on a much larger scale than this literature review) would be necessary to conclude which speed limit arrangement is better
This paper describes a number of individual-choice models of work-trip mode-choice, calibrated in... more This paper describes a number of individual-choice models of work-trip mode-choice, calibrated in the course of a bus study in two communities of Metropolitan Johannesburg. First, it is found to be useful to reduce the alternative set from eight modes to four modes, without loss of estimation power. Second, a number of alternative specifications of costs and times are examined, from which the chosen model is selected as one containing five such variables. In addition, a variable of car competition is found to add significantly to the explanatory power of the model. Finally, recently-documented procedures are applied to the selected model specification to pool the results of two random subsamples and to correct the choice-based biases in the alternative-specific constants. It is found that the coefficients of the South African model fall well within the range of coefficients determined in the U.S.
Transportation Research Part D: Transport and Environment, 2019
Extreme weather days were usually removed as outliers in past studies of taxi ridership. However,... more Extreme weather days were usually removed as outliers in past studies of taxi ridership. However, taxis play an important role during extreme weather events when other public transportation service is suspended. Thus, estimating spatio-temporal variations of taxi ridership during extreme weather conditions can provide valuable information on heretofore relatively unknown behavior of taxi riders and help identify areas with unusual taxi demands. In this study, New York City (NYC) taxi ridership shortly before the landfall of Hurricanes Irene and Sandy was analyzed. It was found that taxi ridership began to drop about 24 h before each hurricane made landfall. Six multisource regression models were estimated to explain the variation of taxi ridership in the last 24 h. Characteristics of the approaching hurricane, local weather conditions, and zonal socio-demographic variables were entered as explanatory variables. It was found that taxi ridership during hurricane-affected periods has a strong linear association with the ridership in unaffected periods but the proportion decreases as the storm approaches; a storm has the greatest impact on taxi ridership during weekend and at night, and the least impact on a weekday during the day; and taxi users make fewer trips during conditions of heavy rain or strong wind. 1. Introduction Taxi is an indispensable component of public transportation system in dense metropolitan areas such as New York City (NYC). According to data in the Census Transportation Planning Package (CTPP), commuting trips by taxi account for 2% of all commuting trips by public transportation within NYC. According to a report published by the Taxi and Limousine Commission (TLC) in 2006, NYC taxi cabs carry 11% of passengers who travel in modes of public transportation (Schaller Consulting, 2006). The most recent TLC report of 2016 states that yellow and green taxis together carry about 474,000 trips per day (NYCTLC, 2016). This statistic can be roughly validated based on data from other sources: the population of NYC is about 8.5 million, the daily person trip rate is about 2.5 trips/person for NYC residents, and about 3% of all-purpose trips use taxi or other similar shared-ride service, which gives 0.64 million taxi trips per day (PSB, 2017; U.S. Census Bureau, 2018). The significance of taxi for NYC is also revealed by the number of active taxi drivers (over 50,000) and the millions of taxi passengers they serve per year (NYCTLC, 2016). According to rules of the TLC, all licensed taxis must install the Taxicab Technology System and taxi owners must ensure this system is constantly maintained (NYCTLC, 2017). The Taxicab Technology System automatically records, collects, and transmits trip
Transportation Research Part C: Emerging Technologies, 2019
Since Hurricane Katrina, transit evacuation service has been seen to serve critical needs in affe... more Since Hurricane Katrina, transit evacuation service has been seen to serve critical needs in affected cities and an increasing number of hurricanes have struck the east coast where more people rely on public transportation to evacuate. Thus, it is important to model mode choice in evacuation for a better estimation of evacuation transit demand. In this study, a joint mode and destination type choice model was estimated based on multiple post-storm behavioral surveys from the northeastern seaboard to the Gulf coast. A Nested Logit model specification was used to estimate this joint choice model. The estimated model showed a significant linkage between mode and destination type choice, which validated the choice of a nested structure for the model. Selected variables include both household and zonal characteristics, reflecting the attributes of alternatives (e.g., hotel price and occupancy), the characteristics of households (e.g., residential stability and community density), and the interactions between them (e.g., average accessibility to a destination type). The use of multiple-storm data allowed the use of some variables that have not been considered in the past because of few variations in their values in a single dataset. Overall, the findings of this study provide insight into the factors affecting mode and destination type choice of residents during hurricane evacuation.
International Journal of Disaster Risk Reduction, 2017
In emergency evacuation there is always a need for transit for those who do not have access to pr... more In emergency evacuation there is always a need for transit for those who do not have access to private transportation or cannot walk to safety. Particularly affected among this section of society are the poor, the disabled, and the elderly. Several cities have established prepositioned pickup points to serve this section of the population but the number and location of the pickup points have usually been decided using professional judgment or based on experience from past storms. As the vulnerable section of the population typically have low mobility, getting transit pickup points close to areas of greatest need is important in order to provide better service, improve the efficiency of evacuation, and even decrease the loss of life. In this study, the spatial distribution of the population is estimated using a modified dasymetric mapping method, which estimates population distribution in terms of 30 m × 30 m land parcels. In each parcel, the vulnerable population is estimated from the proportion of disabled, aged, and zero car-owning persons in the area as determined from census data. Using Orleans parish in New Orleans as a case study and assuming a catchment area of ½ mile around each of the 17 existing pickup points, the number of vulnerable persons served by the existing system was estimated. To determine whether the 17 pickup points could be better located to serve the vulnerable optimally, the set of all eligible pickup sites were first identified and then the pickup points serving the greatest need were identified using integer linear programming. The results show that the 17 optimally located pickup points triple the vulnerable population that could be served. On the question of whether 17 is the right number of pickup points to employ, analysis shows there is a steadily decreasing average value served per pickup point as the number of pickup point increases. At some stage it would probably no longer be efficient to create additional pickup points but provide a feeder service from small demand to larger demand pickup points or link smaller demand pickup points on a route to serve several pickup points with a single service.
International Choice Modelling Conference 2017, Mar 28, 2017
In this study a joint mode and destination type choice model was developed based on evacuation be... more In this study a joint mode and destination type choice model was developed based on evacuation behavior captured in a post hurricane Irene behavior survey. A Nested Logit model specification was used with destination type being modeled in the upper nest and mode choice in the lower nest. As anticipated, the estimated model showed significant dependence between mode and destination type choice. Variables in the model included household socio-demographic characteristics, measures of social connectivity within communities, and a proxy variable of the level of transit service provided in each zone. The study provides insight into some of the factors affecting mode and destination type choice of residents during hurricane evacuation.
The objective of this study was to investigate the feasibility of using a Bluetooth Probe Detecti... more The objective of this study was to investigate the feasibility of using a Bluetooth Probe Detection System (BPDS) to estimate travel time in an urban area. Specifically, the study investigated the possibility of measuring overall congestion, the trend in congestion, the location of congestion “hotspots,” and finally measurement of the level of congestion at the hotspots using a BPDS. A secondary objective was to assess the possibility of obtaining travel time from other quicker and cheaper methods such as simply purchasing it from a commercial vendor. The findings of the study indicate that a BPDS can reliably be used to measure travel time and estimate congestion in terms of indices such as travel delay, planning time index, and travel time index. However, the acquisition of a BPDS includes certain overheads such as installation costs, maintenance costs and monitoring costs. Purchase of travel time from a commercial vendor might be a viable option if the travel time data is not nee...
This paper examines the impact of time-dependent travel cost on hurricane evacuation destination ... more This paper examines the impact of time-dependent travel cost on hurricane evacuation destination choice models based on post hurricane Floyd survey data collected in South Carolina in 1999. The network condition for destination choice model is represented by time dependent origin-destination travel cost. Multinomial logit models were applied for models with travelers evacuating to friends and relatives. The models were applied for all period, peak period and off-peak period. The results show that the dynamic model has less impact overall than the static model with static shortest path travel cost. The travelers have better knowledge of travel cost in off-peak period than in peak period and as a result, the time-dependent travel cost to the destination becomes less important in the peak period model.
The Louisiana Department of Transportation and Development (DOTD) Outsourcing Decision Assistance... more The Louisiana Department of Transportation and Development (DOTD) Outsourcing Decision Assistance Model was developed to assist officials of the DOTD to assess the outsourcing potential of individual activities or functions in the department. The model consists of both a qualitative and a quantitative assessment process which is conducted interactively by a user on a personal computer. The qualitative portion of the model uses the subjective judgment of one or more persons on a set number of perspectives, where each perspective is aimed at a different aspect of the potential for outsourcing. The quantitative portion of the model consists of the comparison of the cost of insourcing or outsourcing the activity. This manual describes how to install and use the computer program that executes both the qualitative and quantitative portions of the model.
AbstractIn this research, the factors affecting route choice in hurricane evacuation are investig... more AbstractIn this research, the factors affecting route choice in hurricane evacuation are investigated. Two hypotheses are tested. First, it is hypothesized that contrary to common practice where travel time is considered the sole or main determinant of route choice, other variables such as familiarity with the route, availability of fuel and shelter, road type, and accessibility of the route have an effect on an evacuees’ route choice as well. The second hypothesis is that as time passes and storm conditions change, the impact each variable has on route choice changes. That is, it is hypothesized that the importance evacuees assign to the factors determining route choice is not static but varies with time. The logit structure was used for modeling the choice process and stated choice data previously collected from the New Orleans area on hypothetical storms was used to calibrate the model. The study found that accessibility to a route, familiarity with the route, road type, length of a route, and availabi...
Page 1. Two dynamic travel demand models for hurricane evacuation based on survival analysis are ... more Page 1. Two dynamic travel demand models for hurricane evacuation based on survival analysis are presented: a Cox proportional hazards model and a piecewise exponential model. ... DemandModels for Hurricane Evacuation Haoqiang Fu and Chester G. Wilmot ...
Uploads
Papers by Chester Wilmot