### Browsing by Author "Zhang, Lei"

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Item An Agent-Based Approach to Travel Demand Modeling: An Exploratory Analysis(Transportation Research Board, 2004) Zhang, Lei; Levinson, David MShow more The paper develops an agent-based travel demand model. In this model, travel demands emerge from the interactions of three types of agents in the transportation system: node, arc and traveler. Simple local rules of agent behaviors are shown to be capable of efficiently solving complicated transportation problems such as trip distribution and traffic assignment. A unique feature of the agent-based model is that it explicitly models the goal, knowledge, searching behavior, and learning ability of related agents. The proposed model distributes trips from origins to destinations in a disaggregate manner and does not require path enumeration or any standard shortest-path algorithm to assign traffic to the links. A sample 10-by-10 grid network is used to facilitate the presentation. The model is also applied to the Chicago sketch transportation network with nearly 1000 trip generators and sinks, followed by a discussion of possible calibration procedures. The agent-based modeling techniques provide a flexible travel forecasting framework that facilitates the prediction of important macroscopic travel patterns from microscopic agent behaviors, and hence encourages the studies on individual travel behaviors. Future research directions are identified, as are the relationship between the agent-based and activity-based approaches for travel forecasting.Show more Item Agent-Based Model of Price Competition and Product Differentiation on Congested Networks.(University of Bath, 2008) Zhang, Lei; Levinson, David M; Zhu, ShanjiangShow more Using consistent agent-based techniques, this research models the decision-making processes of users and infrastructure owner/operators to explore the welfare consequence of price competition, capacity choice, and product differentiation on congested transportation networks. Component models include: (1) An agent-based travel demand model wherein each traveler has learning capabilities and unique characteristics (e.g. value of time); (2) Econometric facility provision cost models; and (3) Representations of road authorities making pricing and capacity decisions. Different from small-network equilibrium models in prior literature, this agent-based model is applicable to pricing and investment analyses on large complex networks. The subsequent economic analysis focuses on the source, evolution, measurement, and impact of product differentiation with heterogeneous users on a mixed ownership network (with tolled and untolled roads). Two types of product differentiation in the presence of toll roads, path differentiation and space differentiation, are defined and measured for a base case and several variants with different types of price and capacity competition and with various degrees of user heterogeneity. The findings favor a fixed-rate road pricing policy compared to complete pricing freedom on toll roads. It is also shown that the relationship between net social benefit and user heterogeneity is not monotonic on a complex network with toll roads.Show more Item An Agent-based Route Choice Model(2007) Zhu, Shanjiang; Levinson, David M; Zhang, LeiShow more Travel demand emerges from individual decisions. These decisions, depending on individual objectives, preferences, experiences and spatial knowledge about travel, are both heterogeneous and evolutionary. Research emerging from fields such as road pricing and ATIS requires travel demand models that are able to consider travelers with distinct attributes (value of time (VOT), willingness to pay, travel budgets, etc.) and behavioral preferences (e.g. willingness to switch routes with potential savings) in a differentiated market (by tolls and the level of service). Traditional trip-based models have difficulty in dealing with the aforementioned heterogeneity and issues such as equity. Moreover, the role of spatial information, which has significant influence on decision-making and travel behavior, has not been fully addressed in existing models. To bridge the gap, this paper proposes to explicitly model the formation and spread- ing of spatial knowledge among travelers. An Agent-based Route Choice (ARC) model was developed to track choices of each decision-maker on a road network over time and map individual choices into macroscopic flow pattern. ARC has been applied on both SiouxFalls network and Chicago sketch network. Comparison between ARC and existing models (UE and SUE) on both networks shows ARC is valid and computationally tractable. To be brief, this paper specifically focuses on the route choice behavior, while the proposed model can be extended to other modules of travel demand under an integrated framework.Show more Item Analysis of the effect of multi-level urban form on bikeshare demand: Evidence from seven large metropolitan areas in the United States(Journal of Transport and Land Use, 2020) Nasri, Arefeh; Younes, Hannah; Zhang, LeiShow more Bikeshare programs in their current form have been in place for several years in many cities across the United States. Encouraging people to use bikeshare for their daily routine travel has numerous social, economic, environmental, and health benefits. Therefore, it is important to understand factors influencing bikeshare use in different urban areas to improve the system and encourage more use. This paper investigates how the built environment at both local and regional scales influences bikeshare use in seven large metropolitan areas in the U.S. The study areas include Boston, Chicago, Philadelphia, Minneapolis, San Francisco, San Jose, and Washington, D.C., and the data consists of about 12 million bike trips from approximately 2,000 stations over a one-year period. In addition to linear regression models built for each individual city for comparison purposes, a multi-level mixed effect regression model is built to predict the number of trips originated from each station with respect to the local and regional built environment pattern. The results are consistent with previous research on the effect of land use at the local level on bikeshare demand and show that residential density, regional diversity, pedestrian-oriented road network density, and job accessibility via transit all have a significant positive effect on bikeshare demand. At the regional level, results suggest that the overall level of mixed-use development and overall bike-friendliness in the region (i.e., exclusive bike routes, right-of-way, and bike facilities) and higher congestion level in the region are significant factors influencing bikeshare activities and demand. Models developed in this study could be applied to other communities that are seeking to improve and/or expand their bikeshare systems, as well as cities planning to launch new bikeshare programs.Show more Item Automorphic forms on certain affine symmetric spaces.(2011-05) Zhang, LeiShow more In this thesis, we consider automorphic periods associated to certain affine symmetric spaces such as the symmetric pairs. In this thesis, we consider automorphic periods associated to certain affine symmetric spaces such as the symmetric pairs (Sp4n; ResK=kSp2n) and (GSp4n; ResK=kGSp2n); where k is a number field and K is an Etale algebra over k of dimension 2. We consider the period integral of a cusp forms of Sp4n(Ak) against with an Eisenstein series of the symmetric subgroup ResK=kSp2n. We expect to establish an identity between this period integrals and the special value of the spin L-function of the symplectic group. In the local theory, using Aizenbud and Gourevitch's generalized Harish-Chandra method and traditional methods, i.e. the Gelfand-Kahzdan theorem, we can prove that these symmetric pairs are Gelfand pairs when Kv is a quadratic extension field over kv for any n, or Kv is isomorphic to kv x kv for n <_ 2. Since (U(J2n; kv(p #28; )); Sp2n(kv)) is a descendant of (Sp4n(kv); Sp2n(kv) #2; Sp2n(kv)), we prove that it is a Gelfand pair for both archimedean and non-archimedean fields. According to the Yu' construction in [76] of irreducible tame supercuspidal representations, we give a parametrization of the distinguished tame supercuspidal representation of symplectic groups in this thesis. Applying the dimension formula of the space HomH(#25;; 1) given by Hakim and Murnaghan [28], we prove that if (G;H) is the symmetric pair (U(J2n;Kv); Sp2n(kv)) there is no H-distinguished tame supercuspidal representation, where Kv is a quadratic extension over kv. In addition, for the symmetric pair (Sp4n(kv); Sp2n(Kv)), we give the sufficient and necessary conditions of generic cuspidal data such that the corresponding tame supercuspidal representations are H-distinguished. Note that our case is the first case worked out with none of G and H being the general linear groups. Furthermore, motivated by a sub-question, we also give an example for the distinguished representations of finite groups of Lie Type in a low rank case. In particular, we show that #18;10 is the unique SL2(Fq2) distinguished cuspidal representation of Sp4(Fq). Note: See PDF abstract for the correct interpretation of the mathematical symbols.Show more Item Balancing Efficiency and Equity of Ramp Meters(American Society of Civil Engineers, 2005) Zhang, Lei; Levinson, David MShow more A new freeway ramp control objective - minimizing total weighted travel time is presented in this study. This new objective function is capable of balancing efficiency and equity of ramp meters, while the previous metering objective - minimizing total absolute travel time is purely efficiency-oriented and hence produces a most efficient but least equitable solution. When certain assumptions hold, this metering objective is shown to be equal to minimizing non-linearly weighted ramp delay. A simulation method to achieve the new metering objective is developed and demonstrated using the example of BEEX, a new ramp control strategy also developed in this study, in a microscopic traffic simulator.Show more Item Business Performance Of Chinese Enterprises In A Relational Perspective(2016-06) Zhang, LeiShow more This study provides a causal explanation and a statistical analysis of how corporate social capital promotes business performance of small- and medium-sized enterprises (SMEs) in China. The central argument of this study is that the formation and mobilization of corporate social capital are culturally and institutionally contextualized. China is an exemplary case. Through interviews and an analysis of 830 SMEs sampled in the Pearl River Delta Region of China, I will show how Chinese SME entrepreneurs formed and mobilized corporate social capital from multiplex and reciprocal strong ties to other entrepreneurs and non-economic organizations, and how such ties increased their business performance. This study makes both theoretical and methodological contributions to social capital research. Theoretically, I conceptualize guanxi, the Chinese expression of social connections, as an isotopic social capital, decompose guanxi to its analytical dimensions, and relate guanxi dimensions to business performance. Methodologically, I construct measures of guanxi ties among Chinese SME entrepreneurs, and for the first time in the long tradition of guanxi research I establish and assess counterfactual models in which to investigate the causal effect of guanxi-based social capital on business performance.Show more Item Determinants of Route Choice and the Value of Traveler Information: A Field Experiment(Transportation Research Board, 2008) Zhang, Lei; Levinson, David MShow more A major strategy of federal ITS initiatives and state departments of transportation is to provide traveler information to motorists through various means, including variable message signs, the internet, telephone services like 511, in-vehicle guidance systems, and TV and radio reports. This is relatively uncontroversial, but its effectiveness is unknown. Drivers receive value from traveler information in several ways, including the ability to save time, but perhaps more importantly, other personal, social, safety, or psychological impacts from certainty. This information can be economically valued. The benefits of reduction in driver uncertainty when information is provided at the beginning of the trip by various means is the main variable we aim to measure in this research, in which we assess user preferences for routes as a function of the presence and accuracy of information, while controlling for other trip and route attributes, such as trip purpose, travel time, distance, number of stops, delay, esthetics, level of commercial development, and individual characteristics. Data is collected in a field experiment in which more than 100 drivers, given real-time travel time information with varying degrees of accuracy, drove four of five alternative routes between a pre-selected OD pair in the Twin Cities metro area. Ordinary regression, multinomial, and rank-ordered logit models produce estimates of the value of information with some variation. In general, results show that travelers are willing to pay up to $1 per trip for pre-trip travel time information. The value of information is higher for commute and event trips and when congestion on the usual route is heavier. The accuracy of the traveler information is also a crucial factor. In fact, there do not seem be incentives for travelers to use traveler information at all unless they perceive it to be accurate. Finally, most travelers (70%) prefer that such information should be provided for free by the public sector, while some (19%) believe that it is better for the private sector to provide such service at a charge. Over 35% of subjects are willing to pay for OD-customized pre-trip travel time information.Show more Item Economics of Road Network Ownership: An Agent-Based Approach(Taylor and Francis, 2009) Zhang, Lei; Levinson, David MShow more This paper seeks to understand the economic impact of centralized and decentralized ownership structures and their corresponding pricing and investment strategies on transportation network performance and social welfare for travelers. In a decentralized network economic system, roads are owned by many agencies or companies that are responsible for pricing and investment strategies. The motivation of this study is two-fold. First, the question of which ownership structure, or industrial organization, is optimal for transportation networks has yet to be resolved. Despite several books devoted to this research issue, quantitative methods that translate ownership-related policy variables into short- and long-run network performance are lacking. Second, the U.S. and many other countries have recently seen a slowly but steadily increasing popularity of road pricing as an alternative to traditional fuel taxes. Not only is the private sector encouraged to finance new roads, this transition in revenue mechanism also makes it possible for lower-level government agencies and smaller jurisdictions to participate in network pricing and investment practice. The issue of optimal ownership is no longer a purely theoretical debate, but bears practical importance. This research adopts an agent-based simulator of network dynamics to explore the implications of centralized and decentralized ownership on mobility and social welfare, as well as potential financial issues and regulatory needs. Components of the simulator: the travel demand model, cost functions, and key variables of pricing and investment strategies, are empirically estimated and validated. Results suggest that road network is a market with imperfect competition. While there is a significant performance lag between the optimal strategy and the current network financing practice in the U.S. (characterized by centralized control, fuel taxes, and budget-balancing investment), a completely decentralized network suffers from issues such as higher-than-optimal tolls and over-investment. For the decentralized ownership structure, appropriate regulation on pricing and investment practices is necessary. Further analysis based on simulation comparisons suggests that with appropriate price regulation, a decentralized road economy consisting of profit-seeking road owners could outperform the existing centralized control, achieve net social benefits close to the theoretical optimum, and distribute a high percentage of welfare gains to travelers. Decentralized control is especially valuable in rapidly changing environments because it promptly responds to travel demand. These results seem to favor the idea of privatizing or decentralizing road ownership on congested networks. Further tests on real-world transportation networks are necessary and should make an interesting future study.Show more Item The Economics of Transportation Network Growth(Springer, 2007) Zhang, Lei; Levinson, David MShow more A number of factors influence the efficiency, productivity, and welfare of a transportation network. Travel demand, user costs, and facility supply costs equilibrate on various time scales under a set of pricing (taxes and tolls), investment and ownership policies. Two types of equilibria exist in a transportation network, short-run traffic equilibrium and long-run supply-demand equilibrium. The phenomenon of traffic equilibrium is explored with a fixed transportation network where the capacity of links is given. Even though investment- and ownership-related policies are not of major concern for studies on traffic equilibrium, it is still a complex problem due to network congestion effects, variations of pricing rules, and multidimensionality of user choices. In order to understand the long-run supply-demand equilibrium in a transportation network, one has to consider all above-mentioned factors in a coherent analytical framework. We refer to this research problem as the transportation network growth problem, because the network evolves and link capacity is not fixed in the long run. Most previous studies have considered network pricing, investment, and ownership structures separately, which are reviewed. The paper considers choices of prices, capacity, and ownership simultaneously on small parallel, serial, and parallel-serial networks, and develops an analytical network model. We discuss properties of long-run network equilibria with different network layouts and ownership regimes, and the implications on network efficiency.Show more Item Estimation of Demand Response to Ramp Metering(American Society of Civil Engineers, 2002) Zhang, Lei; Levinson, David MShow more Ramp meters in the Twin Cities were turned off for 8 weeks in the Fall of 2000. Previous research has assumed demand to be fixed when analyzing ITS technologies, however analysis of this ramp metering shut down experiment, using traffic count data from freeway loop detectors, suggests otherwise: for discretionary trips (non-work trips), the presence of ramp meters encourages people to defer short non-work trips, which then take place during unmetered times. Similarly, the absence of ramp meters discourages long peak-period non-work trips, which are deferred to off-peak times. The effects of ramp metering on non-discretionary demand (work trips) are also reflected by the spreading of the peaks. The method of using freeway traffic count data to estimate demand shifts developed in this paper can also be applied to other freeway demand analyses.Show more Item Evaluating Effectiveness of Ramp Meters: Evidence for the Twin Cities Ramp Meter Shut-off(Kluwer Academic Publishers, 2004) Levinson, David M; Zhang, LeiShow more Ramp meters in the Twin Cities have been turned off for eight weeks in Fall 2000 in an experiment testing their effectiveness. This chapter analyzes the data collected during the experiment on several representative freeways during the afternoon peak period. Several performance measures for ramp metering including mobility, equity, consumers’ surplus, productivity, accessibility and travel time variation are developed and applied to the studied freeways. It is found that ramp meters are particularly helpful for long trips relative to short trips. On TH169, trips more than 3 exits in length benefit, while those 3 exits or less are hurt by ramp meters. Ramp metering, while generally beneficial to freeway mainline, may not improve trip travel times (including ramp delays). Reduction in travel time variation with the presence of ramp metering is observed as another important benefit from ramp meters. The results are mixed, suggesting a more refined ramp control algorithm which explicitly considers ramp delay is in order.Show more Item Exponential Modeling with Unknown Model Order Using Structured Nonlinear Total Least Norm(2000-04-07) Zhang, Lei; Park, Haesun; Rosen, J. BenShow more A method based on Structured Nonlinear Total Least Norm is presented for estimating the parameters of exponentially damped sinusoidal signals in noise when the model order is unknown. It is compared to two other existing methods to show its robustness in recovering correct values of parameters when the model order is unknown, in spite of some large errors in measured data.Show more Item How built environment affects travel behavior: A comparative analysis of the connections between land use and vehicle miles traveled in US cities(Journal of Transport and Land Use, 2012) Zhang, Lei; Hong, Jinhyun; Nasri, Arefeh; Shen, QingShow more Mixed findings have been reported in previous research regarding the impact of built environment on travel behavior—i.e., statistically and practically significant effects found in a number of empirical studies and insignificant correlations shown in many other studies. It is not clear why the estimated impact is stronger or weaker in certain urban areas and how effective a proposed land use change/policy will be in changing certain travel behavior. This knowledge gap has made it difficult for decision makers to evaluate land use plans and policies according to their impact on vehicle miles traveled (VMT), and consequently, their impact on congestion mitigation, energy conservation, and pollution and greenhouse gas emission reduction. This research has several objectives: (1) re-examine the effects of built-environment factors on travel behavior, in particular, VMT in five US metropolitan areas grouped into four case study areas; (2) develop consistent models in all case study areas with the same model specification and data sets to enable direct comparisons; (3) identify factors such as existing land use characteristics and land use policy decision-making processes that may explain the different impacts of built environment on VMT in different urban areas; and (4) provide a prototype tool for government agencies and decision makers to estimate the impact of proposed land use changes on VMT. The four case study areas include Seattle, WA; Richmond-Petersburg and Norfolk-Virginia Beach, VA; Baltimore, MD; and Washington, DC. Our empirical analysis employs Bayesian multilevel modeling method with various person-level socioeconomic and demographic variables, and five built-environment factors including residential density, employment density, entropy (measuring level of mixed-use development), average block size (measuring transit/walking friendliness), and distance to city center (measuring decentralization and level of infill development). Our findings show that promoting compact, mixed-use, small-block, and infill developments can be effective in reducing VMT per person in all four case study areas. However, the effectiveness of land use plans and policies encouraging these types of land development is different both across case study areas and within the same case study area. We have identified several factors that potentially influence the connection between built environment shifts and VMT changes including urban area size, existing built environment characteristics, transit service cover- age and quality, and land use decision-making processes.Show more Item Illusion of Motion: Variation in Travel Time under Different Driving Conditions(Transportation Research Board, 2009) Zhang, Lei; Xie, Feng; Levinson, David MShow more This paper explores drivers' subjective value of time under moving and stopped freeway travel conditions using a stated preference survey. Unlike previous studies that assume a constant value of time, this research relates perceived satisfaction of a freeway trip to its quality indicators. Sixty-nine subjects in the Twin Cities are asked in the survey to rank sixteen driving scenarios in four condition sets with different durations of ramp wait and freeway travel. Several utility functions are specified where the weight of ramp delay is a function of the length of the delay itself and subject specific variables, and the resulting choice models estimated using rank-ordered logit and binary logit techniques. Results suggest that drivers perceive ramp wait as more onerous than freeway travel. Drivers also weight each minute of ramp wait more heavily as the length of the delay gets longer. Although the subjects show some tolerance to the first several minutes of ramp delay (less than 5 minutes), they perceive long delays as much as twelve times more onerous than time in motion. The derived weighting function for ramp wait can improve the design of freeway traffic control strategies that trade-off freeway delay with ramp wait. The findings also enable a more utility-based approach for freeway operations than the current method which has the engineering efficiency objective of minimizing total system delay or maximizing throughput. Minimizing total perceived travel time is probably more appropriate than minimizing total absolute travel time which does not take into account driver acceptance. The weighting function can also be easily transformed into a value of time function for project evaluation purposes.Show more Item Investing for Reliability and Security in Transportation Networks(Transportation Research Board, 2008) Zhang, Lei; Levinson, David MShow more Alternative transportation investment policies can lead to very different network forms in the future. The desirability of a transportation network should be assessed not only by its economic efficiency but also by its reliability and security, because the cost of an incidental capacity loss in a road network can be massive. This research concerns how investment rules shape the hierarchical structure of roads and affect network fragility to natural disasters, congestion, and accidents and vulnerability to targeted attacks. A microscopic network growth model predicts the equilibrium road networks under two alternative policy scenarios: investment based on beneﬁt–cost analysis and investment based on bottleneck removal. A set of Monte Carlo simulation runs, in which a certain percentage of links was removed according to the type of network degradation analyzed, was carried out to evaluate the equilibrium road networks. It was found that a hierarchy existed in road networks for reasons such as economic efficiency but that an overly hierarchical structure had serious reliability problems. Throughout the equilibrating or evolution process, the grid network studied under beneﬁt–cost analysis had better efficiency performance, as well as error and attack tolerance. The paper demonstrates that reliability and security considerations can be integrated into the planning of transportation systems.Show more Item Low Rank Approximation of a Hankel Matrix by Structured Total Least Norm(1997) Park, Haesun; Zhang, Lei; Rosen, J. BenShow more The structure preserving rank reduction problem arises in many important applications. The singular value decomposition (SVD), while giving the best low rank approximation to a given matrix, may not be appropriate for these applications since it does not preserve the given structure. We present a new method for structure preserving low rank approximation of a matri.x, which is based on Structured Total Least Norm (STLN). The STLN is an efficient method for obtaining an approximate solution to the overdetermined linear system AX ~ B preserving the given linear structure in .4. or (A I BJ, where errors can occur in both the right hand side matrix B and the matrix A. The approximate solution can be obtained to minimize the error in the Lp norm, where p = l, 2, or oo. An algorithm is described for Hankel structure preserving low rank approximation using STLN with Lp norm. Computational results are presented, which compare performances of the STLN based method for L1 and L2 norms and other existing methods for reduced rank approximation for Hankel matrices.Show more Item Measuring the Equity and Efficiency of Ramp Meters(2004-11-01) Levinson, David M; Zhang, Lei; Sheikh, AtifShow more Traffic congestion has become an increasingly serious problem in many cities. Ramp metering, which maintains smooth freeway mainline flow by limiting vehicle entry at entrance ramps, has been proposed and implemented in a number of metropolitan areas in and outside the U.S. to mitigate freeway congestion. This study aims to develop both efficient and equitable freeway ramp control strategies. Traffic conditions with and without ramp metering are evaluated on several representative freeways in the Twin Cities with a comprehensive set of performance measures. A unified theory for ramp metering is proposed based on a linear programming model of freeway traffic dynamics. The most efficient ramp control algorithm is found to be also the least equitable one. A novel control objective, minimizing weighted or perceived travel time, is therefore proposed to balance efficiency and equity objectives of ramp metering. This research also develops a new family of applicable ramp metering strategies, which consider both efficiency and equity, and are demonstrated in a microscopic traffic simulator. Future studies should compare various traffic control methods under the analytical framework proposed in this report. Researchers should also pursue field experiments of the proposed multi-objective ramp control strategies.Show more Item A model of the rise and fall of roads(Journal of Transport and Land Use, 2017) Zhang, Lei; Levinson, DavidShow more This paper analyzes the relationship between network supply and travel demand and describes a road development and degeneration mechanism microscopically at the link (road-segment) level. A simulation model of transportation network dynamics is developed, involving iterative evolution of travel demand patterns, network revenue policies, cost estimation, and investment rules. The model is applied to a real-world congesting network for Minneapolis-St. Paul, Minnesota (Twin Cities), which comprises nearly 8,000 nodes and more than 20,000 links, using network data collected since 1978. Four experiments are carried out with different initial conditions and constraints, the results of which allow us to explore model properties such as computational feasibility, qualitative implications, potential calibration procedures, and predictive value. The hypothesis that road hierarchy is an emergent property of transportation networks is corroborated and the underlying reasons discovered. Spatial distribution of capacity, traffic flow, and congestion in the transportation network is tracked over time. Potential improvements to the model, in particular, and future research directions in transportation network dynamics, in general, are also discussed.Show more Item A Model of the Rise and Fall of Roads(University of Minnesota, 2016) Zhang, Lei; Levinson, David MShow more Transportation network planning decisions made at one point of time can have profound impacts in the future. However, transportation networks are usually assumed to be static in models of land use. A better understanding of the natural growth pattern of roads will provide valuable guidance to planners who try to shape the future network. This paper analyzes the relationships between network supply and travel demand, and describes a road development and degeneration mechanism microscopically at the link level. A simulation model of transportation network dynamics is developed, involving iterative evolution of travel demand patterns, network revenue policies, cost estimation,and investment rules. The model is applied to a real-world congesting network – the Twin Cities transportation network which comprises nearly 8,000 nodes and more than 20,000 links, using network data collected since year 1978. Four experiments are carried out with different initial conditions and constraints, the results from which allow us to explore model properties such as computational feasibility, qualitative implications, potential calibration procedures, and predictive value. The hypothesis that road hierarchies are emergent properties of transportation networks is confirmed, and the underlying reasons discovered. Spatial distribution of capacity, traffic flow, and congestion in the transportation network is tracked over time. Potential improvements to the model in particular and future research directions in transportation network dynamics in general are also discussed.Show more