Skip to main content

Michael Kuby

Arizona State University, School of Geographical Sciences and Urban Planning, Faculty Member

Followers

57

Following

3

Co-authors

3

Public Views

University of Zagreb

Uppsala University

University of East London

University of Leicester

Gwen Robbins Schug

University of North Carolina at Greensboro

Gabriel Gutierrez-Alonso

University of Salamanca

Macquarie University

Universidade Federal do Rio Grande do Sul

Swansea University

Jesper Hoffmeyer

University of Copenhagen

Uploads

Papers by Michael Kuby

Comparing the p-median and flow-refueling models for locating alternative-fuel stations

Journal of Transport Geography, Nov 1, 2010

The p-median and flow-refueling models are two of the more popular models for optimal location of... more The p-median and flow-refueling models are two of the more popular models for optimal location of alternative-fuel stations. The p-median model, one of the most widely used location models of any kind, locates p facilities and allocates demand nodes to them to minimize total weighted distance traveled. In comparison, the flow-refueling location model (FRLM) is a path-based demand model that locates p stations to maximize the number of trips on their shortest paths that can be refueled. For a path to be considered refuelable, one or more stations must be located on the path in a way that allows the round trip to be completed without running out of fuel, given the vehicle driving range. In this paper, we analyze how well the facilities located by each model perform on the other's objective function on road networks in Florida. While each objective function degrades somewhat when facilities are located by the other model, the stations located by the flow-refueling model generally do better on the p-median objective than the stations located by the p-median model do on the flow-refueling objective. This difference between the two models is even more pronounced at the state scale than at the metropolitan scale. In addition, the optimal locations for the FRLM tend to be more much more stable as p increases than those located by the p-median model.

The deviation-flow refueling location model for optimizing a network of refueling stations

International Journal of Hydrogen Energy, Mar 1, 2012

This research develops and applies a mixed-integer linear programming model that optimizes the lo... more This research develops and applies a mixed-integer linear programming model that optimizes the locations of fueling stations considering not only the limited driving range of vehicles but also the necessary deviations that drivers are likely to make from their shortest paths in order to refuel their vehicles when the refueling station network is sparse. The Deviation-Flow Refueling Location Model (DFRLM) locates facilities to maximize the total flows refueled on deviation paths. The flow demand captured by the stations is assumed to decrease as the deviation that drivers must make increases. Test results indicate that the maximum allowable deviation and the specific deviation penalty functional form do have a measurable effect on the optimal locations of facilities and objective function values as well.

A Model for Location of Capacitated Alternative-Fuel Stations

Geographical Analysis, 2009

Increased interest in alternative fuels is attributable, in part, to rising oil prices and increa... more Increased interest in alternative fuels is attributable, in part, to rising oil prices and increasing concern about global warming. A lack of a refueling infrastructure, however, has inhibited the adoption of alternative-fuel vehicles. Little economic incentive exists to mass-produce alternative-fuel vehicles until a network of stations exists that can refuel a reasonable number of trips. The flow refueling location model (FRLM) was developed to minimize the investment necessary to create a refueling infrastructure by optimizing the location of fueling stations. The original uncapacitated FRLM assumes that the presence of a refueling station is sufficient to serve all flows passing through a node, regardless of their volume. This article introduces the capacitated flow refueling location model that limits the number of vehicles refueled at each station. It also introduces a modified objective function maximizing vehicle-miles traveled instead of trips, applies both models to an intercity network for Arizona, and formulates several other extensions.

Factors influencing light-rail station boardings in the United States

Transportation Research Part A-policy and Practice, Mar 1, 2004

Many US cities have recently built or approved light-rail systems to combat congestion, sprawl, a... more Many US cities have recently built or approved light-rail systems to combat congestion, sprawl, and pollution. Critics questions light railÕs ability to generate ridership in low-density, automobile-oriented, polycentric US cities with smaller downtowns. Proponents counter that sufficient numbers of homes and workplaces have convenient access to stations via walking, park-and-ride, or bus to develop feasible corridors connecting major residential areas with suburban concentrations of employment and the CBD. With this in mind, we used multiple regression to determine factors that contribute to higher light-rail ridership. Cross-sectional data on average weekday boardings were collected for the year 2000 for 268 stations in nine US cities representing a variety of urban settings. The results showed the importance of land use and accessibility. Employment, population, and percent renters within walking distance, as well as bus lines, park-and-ride spaces, and centrality, were significant. Dummy variables for terminal and transfer stations and international borders were all positive and significant. Total degree-days were negative and significant, lowering expectations for cities with extreme climates. Notably, the stations in the CBD generate much higher boardings, but these are explainable by the same variables present in lesser combinations at non-CBD stations and account for their generally lesser boardings. Importantly, a dummy variable for CBD location was not significant. The resulting model may be useful as a first-cut, one-step approach for predicting demand for possible light-rail alignments.

Reducing Energy Shortages and Pollution in China: The World Bank’s Coal Transport Studies

Springer eBooks, 2004

China, like many developing countries, faces a difficult tradeoff between economic development an... more China, like many developing countries, faces a difficult tradeoff between economic development and environmental protection. Being the world’s largest producer and consumer of coal places a massive burden on China’s transportation and environmental systems. In 1989, energy shortages and runaway pollution prompted the World Bank and the Chinese State Planning Commission (SPC) to jointly undertake the China Coal Transport Study (CTS). At the time, China relied on coal for 73 percent of commercial energy, while coal accounted for 42 percent of rail freight. Rail transport, coal, and electricity were all suffering from debilitating shortages, which threatened China’s 10 percent annual economic growth. Meanwhile, SO2 and particulate levels were among the highest in the world, and CO2 emissions reached 11 percent of the world total — second after the United States.

A new approach to paleoclimatic research using linear programming

Palaeogeography, Palaeoclimatology, Palaeoecology, Apr 1, 1997

One of the most frequently attempted correlations in Quaternary research is between insolation an... more One of the most frequently attempted correlations in Quaternary research is between insolation and paleoclimatic data. Yet there are a large number of insolation time series that could potentially explain a Quaternary dataset, individually or in combination. We computed 342 insolation time series (varying by latitude, time of year and time of day) for fitting to four different paleoclimatic records: foraminiferal 8~so from SPECMAP; temperatures inferred from Vostok, Antarctica ice cores; marine accumulation rates of a freshwater diatom, Melosira, originating from tropical Africa lakebeds; and 5180 variations in calcite at Devil's Hole, Nevada. We developed two "inductive" linear programming models that solve for the weighted combination of insolation curves that minimize either the average or maximum residual from the proxy curve. Each of the four proxy records, lagged and unlagged, was solved by both model types. On average, our composite insolation curves fit the proxy records 48-76% better than does June daily insolation at 60°N, the key insolation curve of the Milankovitch paradigm. Globally, high latitude insolation (60°-70 ° N and S) and insolation at specific times of day (noon or non-noon, as opposed to daily) dominated the results. Regionally, the model tended to select insolation curves from absolute latitudes similar to those of the proxy records. The fact that these results are plausible given known biophysical processes, combined with the fact that a small number of curves repeatedly accounted for a disproportionate share of the explanation, suggest strongly that the correlations found are not happenstance, despite the inductive method used.

The Location Types of US Retailers

International Journal of Applied Geospatial Research, Oct 1, 2016

This manuscript presents the results of an inductive analysis of the types of locations chosen by... more This manuscript presents the results of an inductive analysis of the types of locations chosen by US retailers. Using a large cross-sectional database, including fifty US retail chains and over 70,000 store locations, a classification of retail location types is presented using cluster analysis on situational and trade area data. These data are then applied to create a location profile for each retailer. Based on the results of the first cluster analysis, a second cluster analysis then groups together the chains with the most similar location profiles. A total of twelve distinct location types were identified in the first cluster analysis. Eight groupings of retailers with similar location profiles were identified in the second cluster analysis. Retailers within the same retail business chose similar types of locations and thus were placed in the same clusters. Retailers generally restrict their deployment to one of three overall strategies including metropolitan, large retail areas, or market size variety with specialty retailers favoring large retail areas of urban markets.

Evaluating light rail sketch planning: actual versus predicted station boardings in Phoenix

Transportation, Oct 15, 2013

ABSTRACT In recent years, transit planners are increasingly turning to simpler, faster, and more ... more ABSTRACT In recent years, transit planners are increasingly turning to simpler, faster, and more spatially detailed “sketch planning” or “direct demand” models for forecasting rail transit boardings. Planners use these models for preliminary review of corridors and analysis of station-area effects, instead of or prior to four-step regional travel demand models. This paper uses a sketch-planning model based on a multiple regression originally fitted to light-rail ridership data for 268 stations in nine U.S. cities, and applies it predictively to the Phoenix, Arizona light-rail starter line that opened in December, 2008. The independent variables in the regression model include station-specific trip generation and intermodal–access variables as well as system-wide variables measuring network structure, climate, and metropolitan-area factors. Here we compare the predictions we made before and after construction began to pre-construction Valley Metro Rail predictions and to the actual boardings data for the system’s first 6 months of operations. Depending on the assumed number of bus lines at each station, the predicted total weekday ridership ranged from 24,767 to 37,907 compared with the average of 33,698 for the first 6 months, while the correlation of predicted and observed station boardings ranged from r = 0.33 to 0.47. Sports venues, universities, end-of-line stations, and the number of bus lines serving each station appear to account for the major over- and under-predictions at the station level.

A rental car strategy for commercialization of hydrogen in Florida

International Journal of Hydrogen Energy, Oct 1, 2008

This article proposes a hydrogen rental-car strategy for transitioning from fleets to consumers i... more This article proposes a hydrogen rental-car strategy for transitioning from fleets to consumers in Orlando, Florida. Orlando is the No. 1 tourist destination in the United States, but most car renters visit only a few destinations. A hydrogen rental-car fleet serving this cluster of destinations could provide visitors with a positive first exposure to hydrogen vehicles with minimal commitment, creating hydrogen advocates and potential early adopters in their home regions. The rental-car business combines the logistical advantages of a fleet operation with outreach to many consumers. A hydrogen-powered rental-car fleet at the Orlando International Airport could provide guaranteed demand, supporting an initial rollout of refueling stations. We surveyed 435 rental-car customers in Orlando to understand the idea from the consumer point of view. We analyzed the bundles of destinations visited by the respondents and found that only three stationsdan existing station at the Orlando International Airport plus new stations near the theme parks and in downtown Orlandodcould serve 64% of renters. Half of all respondents indicated a willingness to pay more to rent a hydrogen car, and this subset of customers ranked the ability to use a pollution-free car as the most important factor in their decision. We then identify the major barriers to a hydrogen rental-car business model from the corporate point of view and propose a number of potential solutions. The most significant barrier appears to be the fleet purchase costs, which we think can be offset by the benefits of free media coverage and contained by beginning with converted internal-combustion vehicles and converting eventually to fuel-cell vehicles. We also outline possible synergies with NASA, Disney, refueling stations, manufacturers and state government.

Dispersion of Nodes Added to a Network

Geographical Analysis, Oct 1, 2005

For location problems in which optimal locations can be at nodes or along arcs but no finite domi... more For location problems in which optimal locations can be at nodes or along arcs but no finite dominating set has been identified, researchers may desire a method for dispersing p additional discrete candidate sites along the m arcs of a network. This article develops and tests minimax and maximin models for solving this continuous network location problem, which we call the added‐node dispersion problem (ANDP). Adding nodes to an arc subdivides it into subarcs. The minimax model minimizes the maximum subarc length, while the maximin model maximizes the minimum subarc length. Like most worst‐case objectives, the minimax and maximin objectives are plagued by poorly behaved alternate optima. Therefore, a secondary MinSumMax objective is used to select the best‐dispersed alternate optima. We prove that equal spacing of added nodes along arcs is optimal to the MinSumMax objective. Using this fact we develop greedy heuristic algorithms that are simple, optimal, and efficient (O(mp)). Empirical results show how the maximum subarc, minimum subarc, and sum of longest subarcs change as the number of added nodes increases. Further empirical results show how using the ANDP to locate additional nodes can improve the solutions of another location problem. Using the p‐dispersion problem as a case study, we show how much adding ANDP sites to the network vertices improves the p‐dispersion objective function compared with (a) network vertices only and (b) vertices plus randomly added nodes. The ANDP can also be used by itself to disperse facilities such as stores, refueling stations, cell phone towers, or relay facilities along the arcs of a network, assuming that such facilities already exist at all nodes of the network.

A Minimax Method for Finding the k Best “Differentiated” Paths

Geographical Analysis, Sep 3, 2010

A Minimax Method for Finding the k Best "Differentiated '' Paths In real-world applications, the ... more A Minimax Method for Finding the k Best "Differentiated '' Paths In real-world applications, the k-shortest-paths between a pair of nodes on a network will often be slight variations of one another. This could be a problem f o r many path-based models, particularly those on capacitated networks where different routing alternatives are needed that are less likely to encounter the same capacity constraints. This paper develops a method to solve f o r k diferentiated paths that are relatively short and yet relatively different f r o m one another, but not necessarily disjoint. Our method utilizes the sum of a path's distance plus some fraction of its shared distance with each other path. A minimax algorithm is used to select the path whose largest sum of length, plus shared length vis-6-vis each previously selected path, is as small as possible. W e present computational results f o r the Chinese railway system, comparing the paths generated b y a standard k-shortest-path algorithm with those f r o m our new model. This work was supported by the World Bank, East Asia Department-and particularly Mr. Philip Anderson-and by the Chinese Ministry of Railways. Arizona State University provided sabbatical support to Michael Kuby and hosted the Chinese team. Barbara Trapido-Lurie of ASU made the maps based on the Railway GIS by Ma Jun of Tsinghua University. The algorithm incorporated a k shortest path generator developed earlier by Wang Xuesheng of MOR. Frank Southworth provided useful feedback on our idea and previous research in the area.

Technological Change and the Concentration of the U.S. General Cargo Port System: 1970-88

Economic Geography, Jul 1, 1992

Abstract: The diffusion of containerization has changed not only how general cargo is handled, bu... more

Programming Models for Facility Dispersion: The p-Dispersion and Maxisum Dispersion Problems

Geographical Analysis, Sep 3, 2010

The p-dispersion problem is to locate p facilities on a network so that the minimum separation di... more The p-dispersion problem is to locate p facilities on a network so that the minimum separation distance between any pair of open facilities is maximized. This problem is applicable to facilities that pose a threat to each other and to systems of retail or service franchises. In both of these applications, facilities should be as far away from the closest other facility as possible. A mixed-integer program is formulated that relies on reversing the value of the &I location variables in the distance constraints so that only the distance between pairs of open facilities constrain the maximization. A related problem, the maxisum dispersion problem, which aims to maximize the average separation distance between open facilities, is also formulated and solved. Computational results for both models for locating 5 and 10 facilities on a network of 25 nodes are presented, along with a multicriteria approach combining the dispersion and maxisum problems. The p-dispersion problem has a weak duality relationship with the (p-I)-center problem in that one-half the maximin distance in the p-dispersion problem is a lower bound for the minimax distance in the center problem for (p-1) facilities. Since the p-center problem is often solved via a series of set-covering problems, the p-dispersion problem may prove useful for finding a starting distance for the series of covering problems.

Heuristic algorithms for siting alternative-fuel stations using the Flow-Refueling Location Model

European Journal of Operational Research, Jul 1, 2010

This paper presents three heuristic algorithms that solve for the optimal locations for refueling... more This paper presents three heuristic algorithms that solve for the optimal locations for refueling stations for alternative-fuels, such as hydrogen, ethanol, biodiesel, natural gas, or electricity. The Flow-Refueling Location Model (FRLM) locates refueling stations to maximize the flow that can be refueled with a given number of facilities. The FRLM uses path-based demands, and because of the limitations imposed by the driving range of vehicles, longer paths require combinations of more than one station to refuel round-trip travel. A mixed-integer linear programming (MILP) version of the model has been formulated and published and could be used to obtain an optimal solution. However, because of the need for combinations of stations to satisfy demands, a realistic problem with a moderate size network and a reasonable number of candidate sites would be impractical to generate and solve with MILP methods. In this research, heuristic algorithms—specifically the greedy-adding, greedy-adding with substitution and genetic algorithm—are developed and applied to solve the FRLM problem. These algorithms are shown to be effective and efficient in solving complex FRLM problems. For case study purposes, the heuristic algorithms are applied to locate hydrogen-refueling stations in the state of Florida.

Location of Alternative-Fuel Stations Using the Flow-Refueling Location Model and Dispersion of Candidate Sites on Arcs

Networks and Spatial Economics, Dec 19, 2006

The Flow Refueling Location Model (FRLM) is a flow-intercepting model that locates p stations on ... more The Flow Refueling Location Model (FRLM) is a flow-intercepting model that locates p stations on a network to maximize the refueling of origin-destination flows. Because of the limited driving range of vehicles, network vertices do not constitute a finite dominating set. This paper extends the FRLM by adding candidate sites along arcs using three methods. The first identifies arc segments where a single facility could refuel a path that would otherwise require two facilities at vertices to refuel it. The other methods use the Added-Node Dispersion Problem (ANDP) to disperse candidate sites along arcs by minimax and maximin methods. While none of the methods generate a finite dominating set, results show that adding ANDP sites produces better solutions than mid-path segments or vertices only.

Compressed Natural Gas (CNG) Fleets in Southern California: Variations in Vehicles and Route Types

Transportation Research Board 94th Annual MeetingTransportation Research Board, 2015

A number of vehicle fleets around the world have transitioned to compressed natural gas (CNG), bu... more A number of vehicle fleets around the world have transitioned to compressed natural gas (CNG), but public refueling stations remains sparse away from fleet depots. Given the varied vehicle and route types of fleets, empirical data on their use of public refueling stations is important to understand, because like consumers, fleet drivers face range anxiety and their driving and refueling habits inform key assumptions important to station location. The authors surveyed 127 drivers of CNG fleet vehicles in Los Angeles at six stations across the metropolitan area. The key survey questions concerned the stops immediately before and after refueling, habituality of refueling away from base and fuel tank levels before refueling. The authors demonstrate that regardless of fleet or vehicle type, drivers deviate up to six minutes in order to refuel, and they also do not exhibit significant differences in fuel tank levels at the time of refueling. The authors also observe that 35% of fleet drivers surveyed indicated they were solely reliant upon away-from-base refueling for their operations, but there is variation between vehicle types. These findings demonstrate that fleet drivers do consider station locations away from their base when refueling, and they also indicate that assumptions made within facility location models with respect to fuel tank level and deviation thresholds do not necessarily have to consider the differences in vehicle or route type when employed at a metropolitan or regional scale.

Editorial for the virtual special issue on “Advances in alternative fuel vehicle transportation systems”

Transportation Research Part C-emerging Technologies, 2017

Editorial for the virtual special issue on ''Advances in alternative fuel vehicle transportation ... more Editorial for the virtual special issue on ''Advances in alternative fuel vehicle transportation systems'' q The increasing pace of worldwide modernization and urbanization now requires the creation of more sustainable approaches to mitigate the effects of climate change and to manage large urban population centers. The transportation sector is facing a grand challenge to reduce our dependence on oil, develop new renewable energy sources, and steward our natural environment. Recent technological advances in alternative-fuel vehicles (AFVs) (e.g., electric, natural gas, biofuel, and hydrogen) lend evidence to that continuing evolution. However, before AFVs can be widely adopted in the marketplace, several deficiencies in these systems must first be resolved. For example, more alternative-fuel stations (AFSs) must be built to alleviate range anxiety. New routing and scheduling strategies must be designed for service fleets and public transit systems that employ AFV technologies. Complex (often dynamic and nonlinear) interactions between users, technologies, and the underlying economy need to be better understood. Technologies and systems solutions are thereby needed in order to better understand the interactions between infrastructure, vehicles, and the users. This special issue serves to fill some of these gaps in the literature. We opened the call for papers in January 5, 2015 and were thrilled to receive 35 submissions from the research community. In the end, we accepted 15 articles for publication. These articles cover a range of topics. A number of them deal with electric vehicle (EV) charging infrastructure planning. Fuller provides an overview of different classes of charging infrastructure that include dynamic charging options. Wang et al. consider charging station locations with recharging scheduling for a fleet of EVs. Ghamami et al. propose a general corridor model for designing plug-in EV charging infrastructure as a mixed integer program with nonlinear constraints, solved via a metaheuristic. Guo et al. consider the locations of charging stations within a competitive setting in which multiple providers compete for service from EVs. He et al. conduct a case study of Beijing to explore the institutional and spatial factors associated with different models for locating charging infrastructure. Li et al. consider staging of charging station investments using a multi-period optimization model that is applied to a case study in South Carolina. Brey et al. look at infrastructure design with consideration of refueling behavior for the city of Seville, Spain. Tu et al. consider charging station design for electric taxis. User behavior is a second major topic area covered by the articles. Nourinejad et al. propose a vehicle-to-grid pricesetting scheme that accounts for travelers' time-of-day preferences in conducting activities. Zhang et al. study EV sales in Norway and find significant positive effects from improved battery technology, toll waivers, and charging station density. Yang et al. design a nested logit model to study EV drivers' route choice decisions, and find that drivers are inclined to choose charging stations closer to their origin. The third major topic area is associated with fueling constraints on transport operations. Liu and Schlake study the additional safety risks of liquefied natural gas tank breaching in train derailments. Liu et al. propose customized driving cycles for individual users to evaluate fuel consumption patterns. Keskin and Ҫatay propose an EV routing model with time windows and partial recharge strategies. Ansaripoor et al. study the fleet portfolio management problem considering cost and risk to support dynamic decision-making under uncertainty. The three-way classification above (into infrastructure planning, user behavior, and fueling constraints) is just one of the ways to highlight the diversity of this emerging field in general and our special issue in particular. Classified by energy source, EVs attracted the most interest (10 papers), but the special issue also includes one paper each on hydrogen and LNG, and two papers comparing multiple types of AFVs. By mode, road transport was the overwhelming focus of all except a single paper on rail; however, within the road transport group we have one paper on taxis, one on vans, and two on unspecified types of commercial vehicles doing delivery or service tours. Topically and methodologically, facility location

The Flow Termini Coverage Model for Locating Bike-Sharing Stations

Annals of the American Association of Geographers, Mar 20, 2024

Introduction to the Special Issue on Location Modeling

Networks and Spatial Economics, May 29, 2010

The year 2009 marked the centennial of Alfred Weber's (1909) Theory of the Location of Industries... more The year 2009 marked the centennial of Alfred Weber's (1909) Theory of the Location of Industries, which more than any other single publication launched the field of Location Science. In the ensuing 100 years, the field has changed dramatically. The hand-drawn concentric circles and mechanical devices of the early 20th century were rendered obsolete by the invention of linear programming, digital computers, branch-and-bound, and GIS. On the computational side, simple but efficient greedy, substitution, and Lagrangean-relaxation heuristics have been augmented by newer developments in simulated annealing, genetic algorithms, ant colony optimization, Tabu search, heuristic concentration, as well as other approaches. Models for industrial factories and warehouses now occupy a small space in the field, having been joined by public sector facility location, emergency vehicle posting, special concerns for undesirable and obnoxious facilities, and countless other point, line, and areal facility problems. Researchers have explored different solution spaces (planar, network, discrete, spherical, and hybrid), numerous objectives (single vs. multiple), temporal aspects (static vs. dynamic), the nature of demand (point, planar, path flows), and other problem dimensions. Location researchers approach these issues from a variety of backgrounds: economics, engineering, geography, mathematics and operations research from both academic and business points of view. To bring these varied specialists together, Jonathan Halpern and Michael Goodchild, launched the International Symposium on Locational Decisions (ISOLDE) in 1978, which was held in Banff, Alberta. This symposium has been held every three years since 1978 for an intensive week focused solely on location decision-making. The papers in this special issue of Networks and Spatial Economics are expanded and refined treatments of topics identified at ISOLDE XI, held in Santa Barbara CA in 2008, as central to current scholarly inquiry into locational decisions. However, in no sense are

The geography of advance transit-oriented development in metropolitan Phoenix, Arizona, 2000–2007

Journal of Transport Geography, Mar 1, 2011

Phoenix adopted overlay zoning (an additional, targeted layer of regulations) in some light-rail ... more Phoenix adopted overlay zoning (an additional, targeted layer of regulations) in some light-rail transit (LRT) station areas at the site-selection stage to reduce planning-related uncertainty. This prompts consideration of advance transit-oriented development (TOD)-development that takes place before LRT system operation. In this paper we break down almost $1 billion worth of advance TOD in the Phoenix area by type of TOD, type of station area, and use of overlay zoning. Factor analysis and cluster analysis are applied to GIS-based parcel-level data to identify five distinct station-area types. We then use ANOVA to verify statistically significant relationships between station-area type and: the value of advance TOD, the percentage of parcels with overlay zoning, and the percentage of advance TOD with overlay zoning. The five station-area types, ordered from highest to lowest advance TOD per station, are employment centers; Middle-Income Mixed-Use areas; transportation (park-and-ride) nodes; high population/rental areas; and urban poverty areas. Overlay zoning was used most in areas of urban poverty and least in station-area types with the most single-family housing. Advance TOD coincided strongly with overlay zoning in areas of urban poverty and least in employment and amenity centers.

Comparing the p-median and flow-refueling models for locating alternative-fuel stations

Journal of Transport Geography, Nov 1, 2010

The p-median and flow-refueling models are two of the more popular models for optimal location of... more The p-median and flow-refueling models are two of the more popular models for optimal location of alternative-fuel stations. The p-median model, one of the most widely used location models of any kind, locates p facilities and allocates demand nodes to them to minimize total weighted distance traveled. In comparison, the flow-refueling location model (FRLM) is a path-based demand model that locates p stations to maximize the number of trips on their shortest paths that can be refueled. For a path to be considered refuelable, one or more stations must be located on the path in a way that allows the round trip to be completed without running out of fuel, given the vehicle driving range. In this paper, we analyze how well the facilities located by each model perform on the other's objective function on road networks in Florida. While each objective function degrades somewhat when facilities are located by the other model, the stations located by the flow-refueling model generally do better on the p-median objective than the stations located by the p-median model do on the flow-refueling objective. This difference between the two models is even more pronounced at the state scale than at the metropolitan scale. In addition, the optimal locations for the FRLM tend to be more much more stable as p increases than those located by the p-median model.

The deviation-flow refueling location model for optimizing a network of refueling stations

International Journal of Hydrogen Energy, Mar 1, 2012

This research develops and applies a mixed-integer linear programming model that optimizes the lo... more This research develops and applies a mixed-integer linear programming model that optimizes the locations of fueling stations considering not only the limited driving range of vehicles but also the necessary deviations that drivers are likely to make from their shortest paths in order to refuel their vehicles when the refueling station network is sparse. The Deviation-Flow Refueling Location Model (DFRLM) locates facilities to maximize the total flows refueled on deviation paths. The flow demand captured by the stations is assumed to decrease as the deviation that drivers must make increases. Test results indicate that the maximum allowable deviation and the specific deviation penalty functional form do have a measurable effect on the optimal locations of facilities and objective function values as well.

A Model for Location of Capacitated Alternative-Fuel Stations

Geographical Analysis, 2009

Increased interest in alternative fuels is attributable, in part, to rising oil prices and increa... more Increased interest in alternative fuels is attributable, in part, to rising oil prices and increasing concern about global warming. A lack of a refueling infrastructure, however, has inhibited the adoption of alternative-fuel vehicles. Little economic incentive exists to mass-produce alternative-fuel vehicles until a network of stations exists that can refuel a reasonable number of trips. The flow refueling location model (FRLM) was developed to minimize the investment necessary to create a refueling infrastructure by optimizing the location of fueling stations. The original uncapacitated FRLM assumes that the presence of a refueling station is sufficient to serve all flows passing through a node, regardless of their volume. This article introduces the capacitated flow refueling location model that limits the number of vehicles refueled at each station. It also introduces a modified objective function maximizing vehicle-miles traveled instead of trips, applies both models to an intercity network for Arizona, and formulates several other extensions.

Factors influencing light-rail station boardings in the United States

Transportation Research Part A-policy and Practice, Mar 1, 2004

Many US cities have recently built or approved light-rail systems to combat congestion, sprawl, a... more Many US cities have recently built or approved light-rail systems to combat congestion, sprawl, and pollution. Critics questions light railÕs ability to generate ridership in low-density, automobile-oriented, polycentric US cities with smaller downtowns. Proponents counter that sufficient numbers of homes and workplaces have convenient access to stations via walking, park-and-ride, or bus to develop feasible corridors connecting major residential areas with suburban concentrations of employment and the CBD. With this in mind, we used multiple regression to determine factors that contribute to higher light-rail ridership. Cross-sectional data on average weekday boardings were collected for the year 2000 for 268 stations in nine US cities representing a variety of urban settings. The results showed the importance of land use and accessibility. Employment, population, and percent renters within walking distance, as well as bus lines, park-and-ride spaces, and centrality, were significant. Dummy variables for terminal and transfer stations and international borders were all positive and significant. Total degree-days were negative and significant, lowering expectations for cities with extreme climates. Notably, the stations in the CBD generate much higher boardings, but these are explainable by the same variables present in lesser combinations at non-CBD stations and account for their generally lesser boardings. Importantly, a dummy variable for CBD location was not significant. The resulting model may be useful as a first-cut, one-step approach for predicting demand for possible light-rail alignments.

Reducing Energy Shortages and Pollution in China: The World Bank’s Coal Transport Studies

Springer eBooks, 2004

China, like many developing countries, faces a difficult tradeoff between economic development an... more China, like many developing countries, faces a difficult tradeoff between economic development and environmental protection. Being the world’s largest producer and consumer of coal places a massive burden on China’s transportation and environmental systems. In 1989, energy shortages and runaway pollution prompted the World Bank and the Chinese State Planning Commission (SPC) to jointly undertake the China Coal Transport Study (CTS). At the time, China relied on coal for 73 percent of commercial energy, while coal accounted for 42 percent of rail freight. Rail transport, coal, and electricity were all suffering from debilitating shortages, which threatened China’s 10 percent annual economic growth. Meanwhile, SO2 and particulate levels were among the highest in the world, and CO2 emissions reached 11 percent of the world total — second after the United States.

A new approach to paleoclimatic research using linear programming

Palaeogeography, Palaeoclimatology, Palaeoecology, Apr 1, 1997

One of the most frequently attempted correlations in Quaternary research is between insolation an... more One of the most frequently attempted correlations in Quaternary research is between insolation and paleoclimatic data. Yet there are a large number of insolation time series that could potentially explain a Quaternary dataset, individually or in combination. We computed 342 insolation time series (varying by latitude, time of year and time of day) for fitting to four different paleoclimatic records: foraminiferal 8~so from SPECMAP; temperatures inferred from Vostok, Antarctica ice cores; marine accumulation rates of a freshwater diatom, Melosira, originating from tropical Africa lakebeds; and 5180 variations in calcite at Devil's Hole, Nevada. We developed two "inductive" linear programming models that solve for the weighted combination of insolation curves that minimize either the average or maximum residual from the proxy curve. Each of the four proxy records, lagged and unlagged, was solved by both model types. On average, our composite insolation curves fit the proxy records 48-76% better than does June daily insolation at 60°N, the key insolation curve of the Milankovitch paradigm. Globally, high latitude insolation (60°-70 ° N and S) and insolation at specific times of day (noon or non-noon, as opposed to daily) dominated the results. Regionally, the model tended to select insolation curves from absolute latitudes similar to those of the proxy records. The fact that these results are plausible given known biophysical processes, combined with the fact that a small number of curves repeatedly accounted for a disproportionate share of the explanation, suggest strongly that the correlations found are not happenstance, despite the inductive method used.

The Location Types of US Retailers

International Journal of Applied Geospatial Research, Oct 1, 2016

This manuscript presents the results of an inductive analysis of the types of locations chosen by... more This manuscript presents the results of an inductive analysis of the types of locations chosen by US retailers. Using a large cross-sectional database, including fifty US retail chains and over 70,000 store locations, a classification of retail location types is presented using cluster analysis on situational and trade area data. These data are then applied to create a location profile for each retailer. Based on the results of the first cluster analysis, a second cluster analysis then groups together the chains with the most similar location profiles. A total of twelve distinct location types were identified in the first cluster analysis. Eight groupings of retailers with similar location profiles were identified in the second cluster analysis. Retailers within the same retail business chose similar types of locations and thus were placed in the same clusters. Retailers generally restrict their deployment to one of three overall strategies including metropolitan, large retail areas, or market size variety with specialty retailers favoring large retail areas of urban markets.

Evaluating light rail sketch planning: actual versus predicted station boardings in Phoenix

Transportation, Oct 15, 2013

ABSTRACT In recent years, transit planners are increasingly turning to simpler, faster, and more ... more ABSTRACT In recent years, transit planners are increasingly turning to simpler, faster, and more spatially detailed “sketch planning” or “direct demand” models for forecasting rail transit boardings. Planners use these models for preliminary review of corridors and analysis of station-area effects, instead of or prior to four-step regional travel demand models. This paper uses a sketch-planning model based on a multiple regression originally fitted to light-rail ridership data for 268 stations in nine U.S. cities, and applies it predictively to the Phoenix, Arizona light-rail starter line that opened in December, 2008. The independent variables in the regression model include station-specific trip generation and intermodal–access variables as well as system-wide variables measuring network structure, climate, and metropolitan-area factors. Here we compare the predictions we made before and after construction began to pre-construction Valley Metro Rail predictions and to the actual boardings data for the system’s first 6 months of operations. Depending on the assumed number of bus lines at each station, the predicted total weekday ridership ranged from 24,767 to 37,907 compared with the average of 33,698 for the first 6 months, while the correlation of predicted and observed station boardings ranged from r = 0.33 to 0.47. Sports venues, universities, end-of-line stations, and the number of bus lines serving each station appear to account for the major over- and under-predictions at the station level.

A rental car strategy for commercialization of hydrogen in Florida

International Journal of Hydrogen Energy, Oct 1, 2008

This article proposes a hydrogen rental-car strategy for transitioning from fleets to consumers i... more This article proposes a hydrogen rental-car strategy for transitioning from fleets to consumers in Orlando, Florida. Orlando is the No. 1 tourist destination in the United States, but most car renters visit only a few destinations. A hydrogen rental-car fleet serving this cluster of destinations could provide visitors with a positive first exposure to hydrogen vehicles with minimal commitment, creating hydrogen advocates and potential early adopters in their home regions. The rental-car business combines the logistical advantages of a fleet operation with outreach to many consumers. A hydrogen-powered rental-car fleet at the Orlando International Airport could provide guaranteed demand, supporting an initial rollout of refueling stations. We surveyed 435 rental-car customers in Orlando to understand the idea from the consumer point of view. We analyzed the bundles of destinations visited by the respondents and found that only three stationsdan existing station at the Orlando International Airport plus new stations near the theme parks and in downtown Orlandodcould serve 64% of renters. Half of all respondents indicated a willingness to pay more to rent a hydrogen car, and this subset of customers ranked the ability to use a pollution-free car as the most important factor in their decision. We then identify the major barriers to a hydrogen rental-car business model from the corporate point of view and propose a number of potential solutions. The most significant barrier appears to be the fleet purchase costs, which we think can be offset by the benefits of free media coverage and contained by beginning with converted internal-combustion vehicles and converting eventually to fuel-cell vehicles. We also outline possible synergies with NASA, Disney, refueling stations, manufacturers and state government.

Dispersion of Nodes Added to a Network

Geographical Analysis, Oct 1, 2005

For location problems in which optimal locations can be at nodes or along arcs but no finite domi... more For location problems in which optimal locations can be at nodes or along arcs but no finite dominating set has been identified, researchers may desire a method for dispersing p additional discrete candidate sites along the m arcs of a network. This article develops and tests minimax and maximin models for solving this continuous network location problem, which we call the added‐node dispersion problem (ANDP). Adding nodes to an arc subdivides it into subarcs. The minimax model minimizes the maximum subarc length, while the maximin model maximizes the minimum subarc length. Like most worst‐case objectives, the minimax and maximin objectives are plagued by poorly behaved alternate optima. Therefore, a secondary MinSumMax objective is used to select the best‐dispersed alternate optima. We prove that equal spacing of added nodes along arcs is optimal to the MinSumMax objective. Using this fact we develop greedy heuristic algorithms that are simple, optimal, and efficient (O(mp)). Empirical results show how the maximum subarc, minimum subarc, and sum of longest subarcs change as the number of added nodes increases. Further empirical results show how using the ANDP to locate additional nodes can improve the solutions of another location problem. Using the p‐dispersion problem as a case study, we show how much adding ANDP sites to the network vertices improves the p‐dispersion objective function compared with (a) network vertices only and (b) vertices plus randomly added nodes. The ANDP can also be used by itself to disperse facilities such as stores, refueling stations, cell phone towers, or relay facilities along the arcs of a network, assuming that such facilities already exist at all nodes of the network.

A Minimax Method for Finding the k Best “Differentiated” Paths

Geographical Analysis, Sep 3, 2010

A Minimax Method for Finding the k Best "Differentiated '' Paths In real-world applications, the ... more A Minimax Method for Finding the k Best "Differentiated '' Paths In real-world applications, the k-shortest-paths between a pair of nodes on a network will often be slight variations of one another. This could be a problem f o r many path-based models, particularly those on capacitated networks where different routing alternatives are needed that are less likely to encounter the same capacity constraints. This paper develops a method to solve f o r k diferentiated paths that are relatively short and yet relatively different f r o m one another, but not necessarily disjoint. Our method utilizes the sum of a path's distance plus some fraction of its shared distance with each other path. A minimax algorithm is used to select the path whose largest sum of length, plus shared length vis-6-vis each previously selected path, is as small as possible. W e present computational results f o r the Chinese railway system, comparing the paths generated b y a standard k-shortest-path algorithm with those f r o m our new model. This work was supported by the World Bank, East Asia Department-and particularly Mr. Philip Anderson-and by the Chinese Ministry of Railways. Arizona State University provided sabbatical support to Michael Kuby and hosted the Chinese team. Barbara Trapido-Lurie of ASU made the maps based on the Railway GIS by Ma Jun of Tsinghua University. The algorithm incorporated a k shortest path generator developed earlier by Wang Xuesheng of MOR. Frank Southworth provided useful feedback on our idea and previous research in the area.

Technological Change and the Concentration of the U.S. General Cargo Port System: 1970-88

Economic Geography, Jul 1, 1992

Abstract: The diffusion of containerization has changed not only how general cargo is handled, bu... more

Programming Models for Facility Dispersion: The p-Dispersion and Maxisum Dispersion Problems

Geographical Analysis, Sep 3, 2010

The p-dispersion problem is to locate p facilities on a network so that the minimum separation di... more The p-dispersion problem is to locate p facilities on a network so that the minimum separation distance between any pair of open facilities is maximized. This problem is applicable to facilities that pose a threat to each other and to systems of retail or service franchises. In both of these applications, facilities should be as far away from the closest other facility as possible. A mixed-integer program is formulated that relies on reversing the value of the &I location variables in the distance constraints so that only the distance between pairs of open facilities constrain the maximization. A related problem, the maxisum dispersion problem, which aims to maximize the average separation distance between open facilities, is also formulated and solved. Computational results for both models for locating 5 and 10 facilities on a network of 25 nodes are presented, along with a multicriteria approach combining the dispersion and maxisum problems. The p-dispersion problem has a weak duality relationship with the (p-I)-center problem in that one-half the maximin distance in the p-dispersion problem is a lower bound for the minimax distance in the center problem for (p-1) facilities. Since the p-center problem is often solved via a series of set-covering problems, the p-dispersion problem may prove useful for finding a starting distance for the series of covering problems.

Heuristic algorithms for siting alternative-fuel stations using the Flow-Refueling Location Model

European Journal of Operational Research, Jul 1, 2010

This paper presents three heuristic algorithms that solve for the optimal locations for refueling... more This paper presents three heuristic algorithms that solve for the optimal locations for refueling stations for alternative-fuels, such as hydrogen, ethanol, biodiesel, natural gas, or electricity. The Flow-Refueling Location Model (FRLM) locates refueling stations to maximize the flow that can be refueled with a given number of facilities. The FRLM uses path-based demands, and because of the limitations imposed by the driving range of vehicles, longer paths require combinations of more than one station to refuel round-trip travel. A mixed-integer linear programming (MILP) version of the model has been formulated and published and could be used to obtain an optimal solution. However, because of the need for combinations of stations to satisfy demands, a realistic problem with a moderate size network and a reasonable number of candidate sites would be impractical to generate and solve with MILP methods. In this research, heuristic algorithms—specifically the greedy-adding, greedy-adding with substitution and genetic algorithm—are developed and applied to solve the FRLM problem. These algorithms are shown to be effective and efficient in solving complex FRLM problems. For case study purposes, the heuristic algorithms are applied to locate hydrogen-refueling stations in the state of Florida.

Location of Alternative-Fuel Stations Using the Flow-Refueling Location Model and Dispersion of Candidate Sites on Arcs

Networks and Spatial Economics, Dec 19, 2006

The Flow Refueling Location Model (FRLM) is a flow-intercepting model that locates p stations on ... more The Flow Refueling Location Model (FRLM) is a flow-intercepting model that locates p stations on a network to maximize the refueling of origin-destination flows. Because of the limited driving range of vehicles, network vertices do not constitute a finite dominating set. This paper extends the FRLM by adding candidate sites along arcs using three methods. The first identifies arc segments where a single facility could refuel a path that would otherwise require two facilities at vertices to refuel it. The other methods use the Added-Node Dispersion Problem (ANDP) to disperse candidate sites along arcs by minimax and maximin methods. While none of the methods generate a finite dominating set, results show that adding ANDP sites produces better solutions than mid-path segments or vertices only.

Compressed Natural Gas (CNG) Fleets in Southern California: Variations in Vehicles and Route Types

Transportation Research Board 94th Annual MeetingTransportation Research Board, 2015

A number of vehicle fleets around the world have transitioned to compressed natural gas (CNG), bu... more A number of vehicle fleets around the world have transitioned to compressed natural gas (CNG), but public refueling stations remains sparse away from fleet depots. Given the varied vehicle and route types of fleets, empirical data on their use of public refueling stations is important to understand, because like consumers, fleet drivers face range anxiety and their driving and refueling habits inform key assumptions important to station location. The authors surveyed 127 drivers of CNG fleet vehicles in Los Angeles at six stations across the metropolitan area. The key survey questions concerned the stops immediately before and after refueling, habituality of refueling away from base and fuel tank levels before refueling. The authors demonstrate that regardless of fleet or vehicle type, drivers deviate up to six minutes in order to refuel, and they also do not exhibit significant differences in fuel tank levels at the time of refueling. The authors also observe that 35% of fleet drivers surveyed indicated they were solely reliant upon away-from-base refueling for their operations, but there is variation between vehicle types. These findings demonstrate that fleet drivers do consider station locations away from their base when refueling, and they also indicate that assumptions made within facility location models with respect to fuel tank level and deviation thresholds do not necessarily have to consider the differences in vehicle or route type when employed at a metropolitan or regional scale.

Editorial for the virtual special issue on “Advances in alternative fuel vehicle transportation systems”

Transportation Research Part C-emerging Technologies, 2017

Editorial for the virtual special issue on ''Advances in alternative fuel vehicle transportation ... more Editorial for the virtual special issue on ''Advances in alternative fuel vehicle transportation systems'' q The increasing pace of worldwide modernization and urbanization now requires the creation of more sustainable approaches to mitigate the effects of climate change and to manage large urban population centers. The transportation sector is facing a grand challenge to reduce our dependence on oil, develop new renewable energy sources, and steward our natural environment. Recent technological advances in alternative-fuel vehicles (AFVs) (e.g., electric, natural gas, biofuel, and hydrogen) lend evidence to that continuing evolution. However, before AFVs can be widely adopted in the marketplace, several deficiencies in these systems must first be resolved. For example, more alternative-fuel stations (AFSs) must be built to alleviate range anxiety. New routing and scheduling strategies must be designed for service fleets and public transit systems that employ AFV technologies. Complex (often dynamic and nonlinear) interactions between users, technologies, and the underlying economy need to be better understood. Technologies and systems solutions are thereby needed in order to better understand the interactions between infrastructure, vehicles, and the users. This special issue serves to fill some of these gaps in the literature. We opened the call for papers in January 5, 2015 and were thrilled to receive 35 submissions from the research community. In the end, we accepted 15 articles for publication. These articles cover a range of topics. A number of them deal with electric vehicle (EV) charging infrastructure planning. Fuller provides an overview of different classes of charging infrastructure that include dynamic charging options. Wang et al. consider charging station locations with recharging scheduling for a fleet of EVs. Ghamami et al. propose a general corridor model for designing plug-in EV charging infrastructure as a mixed integer program with nonlinear constraints, solved via a metaheuristic. Guo et al. consider the locations of charging stations within a competitive setting in which multiple providers compete for service from EVs. He et al. conduct a case study of Beijing to explore the institutional and spatial factors associated with different models for locating charging infrastructure. Li et al. consider staging of charging station investments using a multi-period optimization model that is applied to a case study in South Carolina. Brey et al. look at infrastructure design with consideration of refueling behavior for the city of Seville, Spain. Tu et al. consider charging station design for electric taxis. User behavior is a second major topic area covered by the articles. Nourinejad et al. propose a vehicle-to-grid pricesetting scheme that accounts for travelers' time-of-day preferences in conducting activities. Zhang et al. study EV sales in Norway and find significant positive effects from improved battery technology, toll waivers, and charging station density. Yang et al. design a nested logit model to study EV drivers' route choice decisions, and find that drivers are inclined to choose charging stations closer to their origin. The third major topic area is associated with fueling constraints on transport operations. Liu and Schlake study the additional safety risks of liquefied natural gas tank breaching in train derailments. Liu et al. propose customized driving cycles for individual users to evaluate fuel consumption patterns. Keskin and Ҫatay propose an EV routing model with time windows and partial recharge strategies. Ansaripoor et al. study the fleet portfolio management problem considering cost and risk to support dynamic decision-making under uncertainty. The three-way classification above (into infrastructure planning, user behavior, and fueling constraints) is just one of the ways to highlight the diversity of this emerging field in general and our special issue in particular. Classified by energy source, EVs attracted the most interest (10 papers), but the special issue also includes one paper each on hydrogen and LNG, and two papers comparing multiple types of AFVs. By mode, road transport was the overwhelming focus of all except a single paper on rail; however, within the road transport group we have one paper on taxis, one on vans, and two on unspecified types of commercial vehicles doing delivery or service tours. Topically and methodologically, facility location

The Flow Termini Coverage Model for Locating Bike-Sharing Stations

Annals of the American Association of Geographers, Mar 20, 2024

Introduction to the Special Issue on Location Modeling

Networks and Spatial Economics, May 29, 2010

The year 2009 marked the centennial of Alfred Weber's (1909) Theory of the Location of Industries... more The year 2009 marked the centennial of Alfred Weber's (1909) Theory of the Location of Industries, which more than any other single publication launched the field of Location Science. In the ensuing 100 years, the field has changed dramatically. The hand-drawn concentric circles and mechanical devices of the early 20th century were rendered obsolete by the invention of linear programming, digital computers, branch-and-bound, and GIS. On the computational side, simple but efficient greedy, substitution, and Lagrangean-relaxation heuristics have been augmented by newer developments in simulated annealing, genetic algorithms, ant colony optimization, Tabu search, heuristic concentration, as well as other approaches. Models for industrial factories and warehouses now occupy a small space in the field, having been joined by public sector facility location, emergency vehicle posting, special concerns for undesirable and obnoxious facilities, and countless other point, line, and areal facility problems. Researchers have explored different solution spaces (planar, network, discrete, spherical, and hybrid), numerous objectives (single vs. multiple), temporal aspects (static vs. dynamic), the nature of demand (point, planar, path flows), and other problem dimensions. Location researchers approach these issues from a variety of backgrounds: economics, engineering, geography, mathematics and operations research from both academic and business points of view. To bring these varied specialists together, Jonathan Halpern and Michael Goodchild, launched the International Symposium on Locational Decisions (ISOLDE) in 1978, which was held in Banff, Alberta. This symposium has been held every three years since 1978 for an intensive week focused solely on location decision-making. The papers in this special issue of Networks and Spatial Economics are expanded and refined treatments of topics identified at ISOLDE XI, held in Santa Barbara CA in 2008, as central to current scholarly inquiry into locational decisions. However, in no sense are

The geography of advance transit-oriented development in metropolitan Phoenix, Arizona, 2000–2007

Journal of Transport Geography, Mar 1, 2011

Phoenix adopted overlay zoning (an additional, targeted layer of regulations) in some light-rail ... more Phoenix adopted overlay zoning (an additional, targeted layer of regulations) in some light-rail transit (LRT) station areas at the site-selection stage to reduce planning-related uncertainty. This prompts consideration of advance transit-oriented development (TOD)-development that takes place before LRT system operation. In this paper we break down almost $1 billion worth of advance TOD in the Phoenix area by type of TOD, type of station area, and use of overlay zoning. Factor analysis and cluster analysis are applied to GIS-based parcel-level data to identify five distinct station-area types. We then use ANOVA to verify statistically significant relationships between station-area type and: the value of advance TOD, the percentage of parcels with overlay zoning, and the percentage of advance TOD with overlay zoning. The five station-area types, ordered from highest to lowest advance TOD per station, are employment centers; Middle-Income Mixed-Use areas; transportation (park-and-ride) nodes; high population/rental areas; and urban poverty areas. Overlay zoning was used most in areas of urban poverty and least in station-area types with the most single-family housing. Advance TOD coincided strongly with overlay zoning in areas of urban poverty and least in employment and amenity centers.