Public subsidy of transit services has increased dramatically in recent years, with little effect on overall ridership. Quite obviously, a clear understanding of the factors influencing transit ridership is central to decisions on investments in and the pricing and deployment of transit services. Yet the literature about the causes of transit use is quite spotty; most previous aggregate analyses of transit ridership have examined just one or a few systems, have not included many of the external, control variables thought to influence transit use, and have not addressed the simultaneous relationship between transit service supply and consumption. This study addresses each of these shortcomings by (1) conducting a cross-sectional analysis of transit use in 265 US urbanized areas, (2) testing dozens of variables measuring regional geography, metropolitan economy, population characteristics, auto/highway system characteristics, and transit system characteristics, and (3) constructing two-stage simultaneous equation regression models to account for simultaneity between transit service supply and consumption. We find that most of the variation in transit ridership among urbanized areas – in both absolute and relative terms – can be explained by factors outside of the control of public transit systems: (1) regional geography (specifically, area of urbanization, population, population density, and regional location in the US), (2) metropolitan economy (specifically, personal/household income), (3) population characteristics (specifically, the percent college students, recent immigrants, and Democratic voters in the population), and (4) auto/highway system characteristics (specifically, the percent carless households and nontransit/non-SOV trips, including commuting via carpools, walking, biking, etc.). While these external factors clearly go a long way toward determining the overall level of transit use in an urbanized area, we find that transit policies do make a significant difference. The observed range in both fares and service frequency in our sample could account for at least a doubling (or halving) of transit use in a given urbanized area. Controlling for the fact that public transit use is strongly correlated with urbanized area size, about 26% of the observed variance in per capita transit patronage across US urbanized areas is explained in the models presented here by service frequency and fare levels. The observed influence of these two factors is consistent with both the literature and intuition: frequent service draws passengers, and high fares drive them away.

Nature and/or nurture? Analyzing the determinants of transit ridership across US urbanized areas

This document consists of the appendixes to NCHRP Report 541 of the same name, which examines procedures and methods for integrating environmental factors in transportation systems planning and decision making at the statewide, regional, and metropolitan levels. The appendixes are as follows: (A) Strategic Environmental Assessment (SEA) and OECD Guidelines; (B) State Environmental Laws, Regulations and Policies; (C) Results from Statewide, Metropolitan, and Environmental Resource Agencies; and (D) Example Interagency Agreements from Minnesota.

Consideration of Environmental Factors in Transportation Systems Planning: Appendixes

Disruption management for vehicle routing problem with time-window changes

Roadway crashes are an increasing concern worldwide, and pedestrians are among the most vulnerable road users because of several special characteristics, including their fragility. While focusing on pedestrian-involved crashes that occurred far away from intersections, a more systematic investigation is needed to determine whether there is a relationship between the severity of these crashes and the land use types surrounding the crash locations. To investigate this issue, a network-based logistic regression model was employed to assess the impact of the distance between pedestrian-involved crash locations and the centroid of an associated land use of various types. In addition, a set of logistic models was developed to assess the effect of traffic- and environment-related factors, such as daylight and the average annual daily traffic (AADT), on the severity of crashes occurring around each land use. Several types of land use appeared to be influential in predicting pedestrian-involved crash severity. The probability of a severe pedestrian-involved crash increased around commercial land use types including retail stores or night clubs whereas it decreased around university campuses. Moreover, among the crash attributes, daylight contributed to the severity of pedestrian-involved crashes regardless of the surrounding land use type while average traffic was found to be a statistically significant factor for the crashes that occurred particularly around parking lots and office buildings. Pedestrian-involved crashes mostly occurred in the vicinity of office buildings during daylight hours, and the pedestrians were less likely to be severely injured. The findings provided valuable insight into the measurements concerning pedestrian safety with respect to various types of land use.

Investigating Spatial Correlations Between Land Use and Pedestrian Injury Severity in Crashes Occurring Away From Intersections in Northwest Florida

Understanding human mobility patterns is of great importance for a wide range of applications from social networks to transportation planning. Toward this end, the spatial-temporal information of a large-scale dataset of taxi trips was collected via GPS, from March 10 to 23, 2014, in Beijing. The data contain trips generated by a great portion of taxi vehicles citywide. We revealed that the geographic displacement of those trips follows the power law distribution and the corresponding travel time follows a mixture of the exponential and power law distribution. To identify human mobility patterns, a topic model with the latent Dirichlet allocation (LDA) algorithm was proposed to infer the sixty-five key topics. By measuring the variation of trip displacement over time, we find that the travel distance in the morning rush hour is much shorter than that in the other time. As for daily patterns, it shows that taxi mobility presents weekly regularity both on weekdays and on weekends. Among different days in the same week, mobility patterns on Tuesday and Wednesday are quite similar. By quantifying the trip distance along time, we find that Topic 44 exhibits dominant patterns, which means distance less than 10 km is predominant no matter what time in a day. The findings could be references for travelers to arrange trips and policymakers to formulate sound traffic management policies.

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Exploring the Citywide Human Mobility Patterns of Taxi Trips through a Topic-Modeling Analysis

In this survey paper, we critique the optimization studies on the distribution of finished vehicles from automobile manufacturers to dealers in the past three decades and propose promising prospective research to minimize the gap between industrial practice and academic research. First, we identify major decision makers involved in automobile distribution, summarize service models, and briefly describe the automobile shipping practice by transportation mode. After defining the automobile shipping optimization problem at the operational level, we present the automobile distribution problem taxonomy by classifying existing studies by the level of decision making, mode of transportation, and type of optimization decisions. Each subcategory of studies is reviewed in detail through comparisons by objective function, constraints, formulation, solution algorithm, and test instances. We conclude this survey paper by summarizing major review outcomes and proposing potential research directions. This survey will stimulate interested transportation researchers to conduct further research to keep pace with the rapid evolution of the automobile shipping practice.

A survey of finished vehicle distribution and related problems from an optimization perspective

The objective of this study is to quantify the correlation between nearly 100 external factors and over 70 performance measures of the Florida multimodal transportation system, based on the empiric...

Evaluating Correlations of External Factors and Performance Measures of the Multimodal Transportation System in Florida

Evaluating rail transit's comparative advantages in travel cost and time over taxi with open data in two U.S. cities

Since the planning and operations of transportation systems depend on factors ranging from economic to political, which tend to vary significantly over geographic regions (geoRegions), the following research question arises: do transportation topics in various geographic regions differ significantly? A review of existing transportation bibliographic studies shows that the information on the geographic location of study areas is seldom available and thus rarely analyzed. This study thus presents a geoRegion-topic model that extends a widely used topic model, latent Dirichlet allocation, to explore the region-specific characteristics of transportation research based on large-scale bibliographic data collected from Transport Research International Documentation. Top geographic regions that are frequently used as study areas in transportation research are identified at both the country/region and U.S. state levels. The results confirm that transportation research exhibits clear region-specific characteristics, namely each geographic region is associated with a unique transportation topic distribution. After exploring the relation between topic similarity and geographic proximity, we find in general countries/regions that are geographically proximate have quite similar transportation topic distributions, while this correlation cannot be observed at the U.S. state level. Other relevant findings are also reported, along with potential bias in the analysis.

Sajeeb Kirtonia

Papers

A survey of finished vehicle distribution and related problems from an optimization perspective

Evaluating Correlations of External Factors and Performance Measures of the Multimodal Transportation System in Florida

Evaluating rail transit's comparative advantages in travel cost and time over taxi with open data in two U.S. cities

Identifying regional characteristics of transportation research with Transport Research International Documentation (TRID) data