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We introduce a novel optimization problem to support the planning and routing of on‐demand buses in an urban context. We call this problem the on‐demand bus routing problem (ODBRP). Given are a fleet of buses with fixed capacity, a set of bus stations and travel times between them, and a set of transportation requests. Each transportation request consists of a set of potential departure and a set of potential arrival bus stations, as well as a time window, that is, an earliest departure time and a latest arrival time. The aim of the ODBRP is to (1) assign each passenger to a departure and arrival bus station and (2) develop a set of bus routes to fulfill each request in time while minimizing the total travel time of all users. We present the static version of the ODBRP, as well as a straightforward large neighborhood search heuristic to solve it. The performance of the heuristic is established by comparing it to an off‐the‐shelve heuristic solver (LocalSolver). We also use our heuristic to solve (slightly modified instances of) the well‐known dial‐a‐ride problem. The results found by the heuristic for the on‐demand bus system are compared to those of a simulated traditional public bus system with fixed lines and timetables. A thorough analysis of the comparison demonstrates that total user ride times can be significantly lower in an on‐demand public bus system and shows that an on‐demand bus system works best with a large number of small buses. [ABSTRACT FROM AUTHOR]

This paper proposes a new mixed integer programming formulation and branch and cut (BC) algorithm to solve the dial-a-ride problem (DARP). The DARP is a route-planning problem where several vehicles must serve a set of customers, each of which has a pickup and delivery location, and includes time window and ride time constraints. We develop "restricted fragments," which are select segments of routes that can represent any DARP route. We show how to enumerate these restricted fragments and prove results on domination between them. The formulation we propose is solved with a BC algorithm, which includes new valid inequalities specific to our restricted fragment formulation. The algorithm is benchmarked on existing and new instances, solving nine existing instances to optimality for the first time. In comparison with current state-of-the-art methods, run times are reduced between one and two orders of magnitude on large instances. [ABSTRACT FROM AUTHOR]

Paratransit services for people with travel difficulties have received increasing government and community attention due to the aging population. In this paper, we examine an integrated service design approach to customize paratransit services with a ridesharing option for a dial-a-ride (DAR) service. The fundamental challenge of DAR services is a lack of commonality across other services in the process, which results in low vehicle utilization. To mass customize paratransit services systematically, we identify the common service components of different paratransit services under the design framework of product family architecture. We then formulate the community organization's pricing and vehicle scheduling decisions with a ridesharing option for a DAR operation as a two-stage decision model. In stage one of the tactical plan, we determine user tolerance of earlier pick-up and later drop-off times, and a price discount for a shared ride. Based on the user tolerance of a longer traveling time, we optimize the vehicle scheduling of shared service orders. Our experimental results indicate that a ridesharing policy option for a DAR service providing a 20% discount for passengers who accept a 15-min earlier pick-up time or a later drop-off time leads to 15% more people being served. [ABSTRACT FROM AUTHOR]

• Overarching framework that covers non-shared taxi, paratransit, and ridesharing. • Systematic quantification of cost and performance in approximate closed-form formulas. • Insights that could be used to explore operating, pricing, and regulatory strategies. • Analytical results are corroborated by agent-based simulations. The paper presents a general analytic framework to model transit systems that provide door-to-door service. The model includes as special cases non-shared taxi and demand responsive transportation (DRT). In the latter we include both, paratransit services such as dial-a-ride (DAR), and the form of ridesharing (shared taxi) currently being used by crowd-sourced taxi companies like Lyft and Uber. The framework yields somewhat optimistic results because, among other things, it is deterministic and does not track vehicles across space. By virtue of its simplicity, however, the framework yields approximate closed form formulas for many cases of interest. [ABSTRACT FROM AUTHOR]

This paper presents a continuum approximation model for the operating cost of demand responsive transit (DRT) systems in large urban networks. Applications of the proposed model shed light on ways demand and characteristics of the DRT system affect major components of cost: fleet, vehicle hours, and vehicle miles traveled. Verifying the relationship with empirical data, results show an accurate approximation of the operating cost for the paratransit system in New Jersey. Furthermore, we develop a systematic approach for evaluating the efficiency of policy implementations for DRTs. Finally, the circumstances where coordinated taxis could be a cost reduction strategy are identified. [ABSTRACT FROM AUTHOR]

The purpose of this study was to characterize wheelchair tiedown and occupant restraint system (WTORS) usage in paratransit vehicles based on observations of wheelchair and scooter (wheeled mobility devices, collectively, “WhMD”) passenger trips. A retrospective review of on-board video monitoring recordings of WhMD trips was conducted. Four hundred seventy-five video recordings were collected for review and analysis. The use of all four tiedowns to secure the WhMD was observed more frequently for power WhMDs (82%) and manual WhMDs (80%) compared to scooters (39%), and this difference was significant (p< 0.01). Nonuse or misuse of the occupant restraint system occurred during 88% of WhMD trips, and was most frequently due to vehicle operator neglect in applying the shoulder belt. Despite the absence of incidents or injuries in this study, misuse and nonuse of WTORS potentially place WhMD seated passengers at higher risk of injury during transit. These findings support the need for improved vehicle operator training and passenger education on the proper use of WTORS and development of WTORS with improved usability and/or alternative technologies that can be automated or used independently. [ABSTRACT FROM AUTHOR]

In the dial-a-ride services, customers specify pickup and drop-off locations and their times for transport. The operator aims at constructing cheap itineraries while minimizing customer inconvenience. This problem has been studied as the Dial-a-Ride Problem (DARP), which consists of both spatial and temporal factors. This article studies the impact of spatial and temporal variation on multivehicle DARP using route construction heuristics. Our work highlights the impact of these variations on the customer disutility and transportation cost. The study will help the service operators in selecting an appropriate construction heuristic while expanding the DARP service in terms of service area, service duration, or planning for a sudden growth in the number of customers. The results show that if the operator is planning to expand the area of service, the Saving Heuristic is more appropriate for larger operators while Insertion Heuristic with spatial sorting scheme is better for smaller operators with limited number of vehicles. If the operator is expanding the service in terms of service duration, from 8 to 24 hours daily, for instance, or preparing for a growth in the number of customers, the Saving Heuristic is better for both smaller and larger service operators. [ABSTRACT FROM AUTHOR]

Dial-a-ride services provide disabled and elderly people with a personalized mode of transportation to preserve their mobility. Typically, several users with different pickup and dropoff locations are transported on a vehicle simultaneously. The focus in dial-a-ride problems (DARPs) is mainly on minimizing routing cost. Service quality has been taken into account in the models by imposing time windows and limiting the maximum ride time of each user. We extend the classical DARP by an additional feature of service quality referred to as driver consistency. Customers of dial-a-ride services are often sensitive to changes in their daily routine. This aspect includes the person who is providing the transportation service, i.e., the driver of the vehicle. Our problem, called the driver consistent dial-a-ride problem (DC-DARP), considers driver consistency by bounding the maximum number of different drivers that transport a user over a multi-period planning horizon. We propose different formulations of the problem and examine their efficiency when applied in a Branch-and-Cut fashion. Additionally, we develop a large neighborhood search algorithm that generates near-optimal solutions in a short amount of time. Over 1000 instances are generated with close reference to real world scenarios. Extensive computational experiments are conducted in order to assess the quality of the solution approaches and to provide insights into the new problem. Results reveal that the cost of offering driver consistency varies greatly in magnitude. Depending on the instance, the cost of assigning one driver to each user can be up to 27.98% higher compared to a low-cost solution. However, routing cost increases by not more than 5.80% if users are transported by at least two drivers. [ABSTRACT FROM AUTHOR]

Developing demand responsive transit systems are important with regard to meeting the travel needs for elderly people. Although Dial-a-ride Problems (DARP) have been discussed for several decades, most researchers have worked to develop algorithms with low computational cost under the minimal total travel costs, and fewer studies have considered how changes in travel time might affect the vehicle routes and service sequences. Ignoring such variations in travel time when design vehicle routes and schedules might lead to the production of inefficient vehicle routes, as well as incorrect actual vehicle arrival times at the related nodes. The purpose of this paper is to construct a DARP formulation with consideration of time-dependent travel times and utilizes the traffic simulation software, DynaTAIWAN, to simulate the real traffic conditions in order to obtain the time-dependent travel time matrices. The branch-and-price approach is introduced for the time-dependent DARP and tested by examining the sub-network of Kaohsiung City, Taiwan. The numerical results reveal that the length of the time window can significantly affect the vehicle routes and quantitative measurements. As the length of the time window increases, the objective value and the number of vehicles will reduce significantly. However, the CPU time, the average pickup delay time, the average delivery delay time and the average actual ride time (ART)/direct ride time (DRT) will increase significantly as the length of the time window increases. Designing the vehicle routes to reduce operating costs and satisfy the requirements of customers is a difficult task, and a trade-off must be made between these goals. Copyright © 2014 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

This is the preliminary finding of a study elaborating the total energy consumption when paratransits in Bandung are altered into electric and the scenario to fulfill it. Therefore, there are lots to be done further concerning result of this initial research, of which will be discussed in another publication. In this paper calculation was done to find out the volume of power needed to fuel electric paratransits in Bandung. Steps carried out include computing total energy consumption for all paratransits, clustering stations from classified routes established by local Department of Transport, and estimating the electricity demand in every clustered station. Data used for this study was acquired from Badan Pusat Statistik Kota Bandung and PT PLN DJA APD Jawa Barat and Banten. A total demand of 61.12 MWh per month will surface to charge the total of 5,521 paratransits from 38 available routes in 15 clustered stations under the assumptions that all paratransits only make 6 return travels per day, operate 30 days per month, and use batteries with 50% State of Charge. [ABSTRACT FROM AUTHOR]

These days, transportation and logistic problems in large cities are demanding smarter transportation services that provide flexibility and adaptability. A possible solution to this arising problem is to compute the best routes for each new scenario. In this problem, known in the literature as the dial-a-ride problem, a number of passengers are transported between pickup and delivery locations trying to minimize the routing costs while respecting a set of prespecified constraints. This problem has been solved in the literature with several approaches from small to medium sized problems. However, few efforts have dealt with large scale problems very common in massive scenarios (big cities or highly-populated regions). In this study, a new distributed algorithm based on the partition of the requests space and the combination of the routes is presented and tested on a set of 24 different scenarios of a large-scale problem (up to 16,000 requests or 32,000 locations) in the city of San Francisco. The results show that, not only the distributed algorithm is able to solve large problem instances that the corresponding sequential algorithm is unable to solve in a reasonable time, but also to have an average improvement of 9% in the smaller problems. The results have been validated by means of statistical procedures proving that the distributed algorithm can be an effective way to solve high dimensional dial-a-ride problems. [ABSTRACT FROM AUTHOR]

A dynamic time window relates to two operations that must be executed within a given time meaning that the difference between the points in time when the two operations are performed is bounded from above. The most prevalent context of dynamic time windows is when precedence is given for the two operations so that it is a priori specified that one operation must take place before the other. A prominent vehicle routing problem with dynamic time windows and precedence is the dial-a-ride problem (DARP), where user-specified transportation requests from origin to destination points must be serviced. The paper presents a new branch-and-cut-and-price solution approach for the DARP, the prototypical vehicle-routing problem with ordinary and dynamic time windows. For the first time (to our knowledge), both ordinary and dynamic time windows are handled in the column-generation subproblem. For the solution, an effective column-generation pricing procedure is derived that allows fast shortest-path computations due to new dominance rules. The new approach is compared with alternative column-generation algorithms that handle dynamic time windows either as constraints of the master program or with less effective labeling procedures. Computational experiments indicate the superiority of the new approach. [ABSTRACT FROM AUTHOR]

Almost all Dial-a-Ride problems (DARP) described in the literature pertain to the design of optimal routes and schedules for n customers who specify pick-up and drop-off times. In this article we assume that the customer is mainly concerned with the drop-off time because it is the most important to the customer. Based on the drop-off time specified by the customer and the customer's location, a pick-up time is calculated and given to the customer by the dispatching office. We base our formulation on a dynamic fuzzy logic approach in which a new request is assigned to a vehicle. The fuzzy logic algorithm chooses the vehicle to transport the customer by seeking to satisfy two objectives. The first reflects the customer's preference and minimizes the time a customer spends in the vehicle, and the second reflects the company's preference and minimizes the distance a vehicle needs to travel to transport the customer. The proposed heuristic algorithm is relatively simple and computationally efficient in comparison with most deterministic algorithms for solving both small and large sized problems. [ABSTRACT FROM AUTHOR]

Highlights: [•] A new VNS algorithm is proposed for solving a DARP. [•] Several neighborhood classes and different schemes for combining them are proposed. [•] The algorithm is tested on demanding scenarios in the city of San Francisco. [•] The results have been compared against state of the art algorithms. [•] According to statistical tests, the proposal has obtained the best results. [ABSTRACT FROM AUTHOR]

Older adults, low-income individuals, and individuals with disabilities are generally considered 'low-mobility' individuals, having less access to transportation options and often marginalized in the social environment of the community. This study assessed the transportation needs of low-mobility individuals using three dimensions: (1) travel characteristics, (2) social strength in terms of transportation assistance received from their social networks, and (3) accessibility to public transportation. A mixed survey method combining an in-person interview at the collaborating organizations and a mail-back survey were used. Results showed that older adults remain mobile and make more frequent short trips. The results also showed a much higher reliance on private vehicles among older adults and individuals with low income, whereas a much higher reliance on public transportation and much lower reliance on private transportation was found among individuals with disabilities. Individuals with disabilities were still active, as almost half of them travel to work frequently. However, the number of nonwork trips made by individuals with disabilities was significantly low. These findings indicated a positive relationship between transportation mode choices and social dependence with family and friends. Individuals with stronger family social ties were more likely to receive adequate help meeting their transportation needs. The accessibility analysis revealed that low-mobility individuals in Cache County, Utah, have difficulties accessing transit due to the long walking distances from their residences. These findings may be used to guide policy for improving public transportation and paratransit services to meet low-mobility individuals' needs. [ABSTRACT FROM AUTHOR]

Abstract: In the Dial-a-Ride Problem (DARP) the aim is to design vehicle routes for a set of users who must be transported between given origin and destination pairs, subject to a variety of side constraints. The standard DARP objective is cost minimization. In addition to cost, the objectives considered in this paper include three terms related to quality of service. This gives rise to a multicriteria problem. The problem is solved by means of a flexible and simple metaheuristic which efficiently integrates the reference point method for multicriteria optimization within a tabu search mechanism. Extensive tests were performed on randomly generated data and on real-life data provided by a major transporter in the Montreal area. Results indicate that the algorithm can yield a rich set of non-dominated solutions. It can also be employed to determine good trade-offs between cost and quality of service. [Copyright &y& Elsevier]

This paper introduces the probabilistic dial-a-ride problem, and describes an efficient request-relocation neighborhood evaluation procedure for the problem. The running time of the procedure is $${\mathcal{O}(n^5)}$$ , compared to $${\mathcal{O}(n^6)}$$ for a straightforward approach. For solving the problem we embed the suggested evaluation procedure in a pure local search heuristic and in a tabu search heuristic. The quality of the solutions obtained by the two heuristics have been compared experimentally. Computational results confirm that our neighborhood evaluation technique is much faster than the straightforward one, and for cases with 144 users and 4 vehicles it is demonstrated that the computation time can be reduced by a factor larger than 27. [ABSTRACT FROM AUTHOR]

Abstract: Dial-a-ride problems deal with the transportation of people between pickup and delivery locations. Given the fact that people are subject to transportation, constraints related to quality of service are usually present, such as time windows and maximum user ride time limits. In many real world applications, different types of users exist. In the field of patient and disabled people transportation, up to four different transportation modes can be distinguished. In this article we consider staff seats, patient seats, stretchers and wheelchair places. Furthermore, most companies involved in the transportation of the disabled or ill dispose of different types of vehicles. We introduce both aspects into state-of-the-art formulations and branch-and-cut algorithms for the standard dial-a-ride problem. Also a recent metaheuristic method is adapted to this new problem. In addition, a further service quality related issue is analyzed: vehicle waiting time with passengers aboard. Instances with up to 40 requests are solved to optimality. High quality solutions are obtained with the heuristic method. [Copyright &y& Elsevier]

Abstract: Using GIS to evaluate travel behaviour is an important technique to increase our understanding of the relationship between accessibility and transport demand. In this paper, the activity space concept was used to identify the nature of participation in activities (or lack of it) amongst a group of students using a 2day travel–activity diary. Three different indicators such as the number of unique locations visited, average daily distance travelled, and average daily activity duration were used to measure the size of activity spaces. These indicators reflect levels of accessibility, personal mobility, and the extent of participation, respectively. Multiple regression analyses were used to assess the impacts of students socio-economic status and the spatial characteristics of home location. Although no differences were found in the levels of accessibility and the extent of participation measures, home location with respect to a demand responsive transport (DRT) service was found to be the most important determinant of their mobility patterns. Despite being able to travel longer distances, students who live outside of the DRT service area were found to be temporally excluded from some opportunities. Student activity spaces were also visualised within a GIS environment and a spatial analysis was conducted to underpin the evaluation of the performance of the DRT. This approach was also used to identify the activity spaces of individuals that are geographically excluded from the service. Evaluation of these results indicated that although the service currently covers areas of high demand, 90% of the activity spaces remained un-served by the DRT service. Using this data six new routes were designed to meet the coverage goal of public transport based on a measure of network impedance based on inverse activity density. Following assessment of public transport service coverage, the study was extended using a spatial multi criteria evaluation (SMCE) technique to assess the effect of service provision on patronage. [Copyright &y& Elsevier]

Abstract: Paratransit is a flexible demand-responsive form of public transportation intended for transporting mobility impaired individuals. This is the first study that estimates both demand and cost functions for publicly provided paratransit in the United States and the first to conduct a benefit-cost analysis for this mode. We find that the benefits of paratransit far exceed its associated costs. The results suggest that paratransit riders have few transportation alternatives available to them. We also find that the level of service matters in the demand for paratransit. [ABSTRACT FROM AUTHOR]

An innovative solution to improve the current service efficiency in paratransit is introduced. The conventional pickup procedure requires reservations in advance for the paratransit operator to meet passengers at designated locations and missed pickups may occur due to the ambiguity of the address information or the inability of finding a specific location. With the availability of existing mobile global positioning system (GPS) devices, passengers can be located instantly, which ensures a successful pickup. This research explores the potential feasibility of using mobile GPS devices to reduce the number of missed pickups. Two GPS-tracking devices were tested and a prototype was also developed. Under this prototype, the agency dispatcher can see both the vehicle and the passenger and therefore instantly supervise the pickup if any errors occur. As new features can be added to the prototype system and new technologies become available, opportunities for future work are also presented. [ABSTRACT FROM AUTHOR]

On the Dial-a-Ride with time windows (DARPTW) customer transportation problem, there is a set of requests from customers to be transported from an origin place to a delivery place through a locations network, under several constraints like the time windows. The problem complexity (NP-Hard) forces the use of heuristics on its resolution. In this context, the application of Genetic Algorithms (GA) on DARPTW was not largely considered, with the exception of a few researches. In this work, under a restrictive scenario, a GA model for the problem was developed based on the adaptation of a generic GA model from literature. Our solution applies data pre-processing techniques to reduce the search space to points that are feasible regarding time windows constraints. Tests show competitive results on Cordeau & Laporte benchmark datasets while improving processing times. [ABSTRACT FROM AUTHOR]

We consider a dynamic planning problem for paratransit transportation. The focus is on a decision to take one day ahead: which requests to serve with own vehicles, and which requests to subcontract to taxis? We call this problem the day-ahead paratransit planning problem. The developed model is a non-standard two-stage integer recourse model. Both stages consist of two consecutive optimization problems: the clustering of requests into routes, and the assignment of these routes to vehicles. To solve this model, a genetic algorithm approach is used. Computational results are presented for randomly generated data sets. [ABSTRACT FROM AUTHOR]

The Dial-a-Ride Problem (DARP) consists of designing vehicle routes and schedules for n users who specify pickup and delivery requests between origins and destinations. The aim is to plan a set of m minimum cost vehicle routes capable of accommodating as many users as possible, under a set of constraints. The most common example arises in door-to-door transportation for elderly or disabled people. The purpose of this article is to review the scientific literature on the DARP. The main features of the problem are described and a summary of the most important models and algorithms is provided. [ABSTRACT FROM AUTHOR]

The rapid pace of motorization throughout the world has changed travel behavior, which in turn has influenced every aspect of transport operations. This impact has also increasingly challenged the future existence of such road-based urban public transport as paratransit due to its characteristics and problems, especially in developing countries. Since creating satisfied users can help retain paratransit’s existence, this research aims to explore user satisfaction with paratransit service in order to anticipate future implications for its competition with motorization in Bandung, Indonesia. It establishes important factors and attributes to explain user perceptions and priorities regarding the service. Its hypotheses explain how users measure paratransit’s quality of service, inferring that they are likely to continue to use it. Even though users are dissatisfied with several aspects of paratransit, and the impact of competition has been strong, loyal users can still be found. By considering the findings, existing problems of inappropriate-quality service can be addressed to satisfy users’ expectations. The study also suggests some anticipation of winning the competition with motorization. [ABSTRACT FROM AUTHOR]

Flexible transport services (FTS) have been of increasing interest in developing countries as a bridge between the use of personal car travel and fixed route transit services. This paper reports on findings from a recent study in Queensland Australia, which identified lessons from an international review and implications for Australia. Potential strategic directions, including a vision, mission, key result areas, strategies, and identified means of measuring performance are described. Evaluation criteria for assessing flexible transport proposals were developed, and approaches to identifying and assessing needs and demands outlined. The use of emerging technologies is also a key element of successful flexible transport services. [ABSTRACT FROM AUTHOR]

Abstract: We study the problem of determining the number of vehicles needed to provide a demand responsive transit service with a predetermined quality for the user in terms of waiting time at the stops and maximum allowed detour. We propose a probabilistic model that requires only the knowledge of the distribution of the demand over the service area and the quality of the service in terms of time windows associated of pickup and delivery nodes. This methodology can be much more effective and straightforward compared to a simulation approach whenever detailed data on demand patterns are not available. Computational results under a fairly broad range of test problems show that our model can provide an estimation of the required size of the fleet in several different scenarios. [Copyright &y& Elsevier]

Aging is commonly associated with an increase in chronic disease and disability, affecting access to transportation. This study examines factors that contribute to the decision to use Handy Dart transportation (a handicap-specialized service) among 869 elderly, chronically ill residents of a metropolitan region in British Columbia. Drawing on Chappell's complementary model of support, the authors hypothesized that informal social support will be positively associated with specialized transportation service use. The authors employ the Andersen-Newman model of health use to help organize the other expected predictors. Results of logistic regression analysis revealed that the presence of regular social support, a positive attitude about Handy Dart helpfulness, being retired, disability because of arthritis, and perceived ill health were the strongest predictors of use. Age, gender, marital status, knowledge, and number of comorbid illnesses did not predict use of the service. The results are discussed within the context of changing needs for specialized transportation services. [ABSTRACT FROM AUTHOR]

This paper estimates the demand for transportation systems that are used primarily by disabled individuals. These systems are known as paratransit systems and have experienced large increases in number and average size over the past 15 years. We first use a national database and standard time series techniques to model aggregate demand. We then use a unique data set of administrative records from a paratransit system in central Virginia to estimate standard and nonstandard count models of individual demand. We conclude that most of the demand growth is from new passengers, but that predicting the growth of new passengers is very difficult. Our results also highlight the importance of incorporating autocorrelation and possible sample attrition into standard count models. [Copyright &y& Elsevier]

Over the past 10 years, operating expenses for demand responsive transit (DRT) have more than doubled as demand for this mandated service has expanded. The DRT systems that we studied consist of dial-a-ride programs that transit agencies use for point-to-point pick-up and delivery of the elderly and handicapped. Many advanced technologies and management practices have been proposed and implemented to improve the efficiency of the service; but, evidence for the effectiveness of these actions has been based upon projections or small pilot studies. We present the results of a nationwide study involving 62 transit agencies. Our analysis indicates that the use of paratransit computer aided dispatching (CAD) system and agency service delivery provide a productivity benefit while the use of financial incentives has a detrimental impact on productivity. Also, the use of advanced communication technology has a beneficial impact on operating cost while the use of financial incentives has a detrimental impact. [Copyright &y& Elsevier]

In the Dial-a-Ride problem (DARP) users specify transportation requests between origins and destinations to be served by vehicles. In the dynamic DARP, requests are received throughout the day and the primary objective is to accept as many requests as possible while satisfying operational constraints. This article describes and compares a number of parallel implementations of a Tabu search heuristic previously developed for the static DARP, i.e., the variant of the problem where all requests are known in advance. Computational results show that the proposed algorithms are able to satisfy a high percentage of user requests. [Copyright &y& Elsevier]

Dial-a-ride is an emerging alternative to traditional public transportation systems. The aim of this paper is to reduce the gap between the models studied in optimization literature and the requirements of practical applications. We also describe the algorithms implemented in DARIA, a PC program for the optimization of static and dynamic dial-a-ride problems. We briefly illustrate two case studies and future developments of the DARIA project. [ABSTRACT FROM AUTHOR]

The article presents information on how the authors prepared a route developer for use in a para-transit environment. They developed a software package that could identify the best scheduling of pickup and deliveries of clients. They discuss the para-transit needs fulfilled by the Memphis Area Transit Authority (MATA) in Tennessee, which provides transportation services for those with special -needs, under the program called MATA+. They discuss the problems faced by the present transportation system in Shelby County, Tennessee. The project developed by them will help schedulers in devising appropriate routes.

The Americans with Disabilities Act (1990) requires providers of fixed-route public transit services to also offer a 'comparable' level of paratransit service for eligible consumers with disabilities who are unable to access the fixed-route system. In this study, one comparable paratransit service is rated for satisfaction by consumers with disabilities (N=482). Particularly troubling were the levels of satisfaction with regard to age and mobility. Younger consumers and those with greater mobility limitations appear to be the least satisfied. These findings should be of particular interest to rehabilitation specialists as reliable transportation modes are essential to employment and community living for people with disabilities. [ABSTRACT FROM AUTHOR]

The Americans with Disabilities Act (ADA) sets far-reaching obligations for public transit. In addition to assuring vehicle accessibility to people with disabilities, operators must provide complementary paratransit to people unable to use regular public transportation. In setting these requirements, the ADA incorporated historical tensions between "effective mobility" and "full access to public transit" as appropriate goals of disability transportation policy. Currently, the demand for complementary paratransit is likely to increase rapidly. This may spur agencies to seek improvements to divert some disabled passengers from expensive paratransit to accessible mainline public transportation. In this fashion, the ADA may inadvertently have created an incentive system to augment a standards-based approach to facilitate disabled transit accessibility. This study examines the interplay of these standards-based and incentive-based approaches through a review of relevant literature and consideration of issues relevant to transit planning for people with disabilities. In addition, the study documents qualitative and experimental findings from Ann Arbor, Michigan, regarding demand management for paratransit services via pricing and information provision. While information and appeals for voluntary reduction in paratransit use had no effect on ridership, elimination of fixed route transit fares to eligible travelers appeared to induce some diversion of paratransit trips to mainline public transportation. Even with relatively low cross-elasticities of paratransit demand with fixed route transit price, fare reduction or elimination strategies can be cost effective when marginal costs differ greatly between the modes. [ABSTRACT FROM AUTHOR]

This paper summarizes the current capabilities of computer dispatch and scheduling systems for taxi and paratransit operations; costs, economic benefits and other impacts of these systems; and future technological directions. Computer dispatch has improved company operations and response time. In the future, however, computer dispatch, passenger codes, locator numbers and caller identification technology will make only marginal improvements on response time. The scheduling of paratransit trips is more complex than taxi dispatching because of the shared-ride nature of these trips. The shared-ride scheduling problem, however, is facilitated by preparing the routes and passenger pickup sequence in advance, typically the night before trips are needed.

This paper modifies the exact Dynamic Programming algorithm developed by the author for the single vehicle many-to-many immediate request Dial-A-Ride problem to solve the problem where each customer has specified upper and lower bounds for his pickup and delivery times and where the objective is to minimize the time needed to service all customers. The major difference between the two algorithms is the substitution of backward recursion with forward recursion. The new algorithm requires the same computational effort as the old one (0(N²3N) for N customers) and is able to recognize infeasible problem instances. [ABSTRACT FROM AUTHOR]

An investigation of the single-vehicle, many-to-many, immediate-request dial-a-ride problem is developed in two parts (I and II). Part I focuses on the "static" case of the problem. In this case, intermediate requests that may appear during the execution of the route are not considered. A generalized objective function is examined, the minimization of a weighted combination of the time to service all customers and of the total degree of "dissatisfaction" experienced by them while waiting for service. This dissatisfaction is assumed to be a linear function of the waiting and riding times of each customer. Vehicle capacity constraints and special priority rules are part of the problem. A Dynamic Programming approach is developed. The algorithm exhibits a computational effort which, although an exponential function of the size of the problem, is asymptotically lower than the corresponding effort of the classical Dynamic Programming algorithm applied to a Traveling Salesman Problem of the same size. Part II extends this approach to solving the equivalent "dynamic" case. In this case, new customer requests are automatically eligible for consideration at the time they occur. The procedure is an open-ended sequence of updates, each following every new customer request. The algorithm optimizes only over known inputs and does not anticipate future customer requests. Indefinite deferment of a customer's request is prevented by the priority rules introduced in Part L Examples in both "static" and "dynamic" cases are presented. [ABSTRACT FROM AUTHOR]

An analytic investigation into the fundamental aspects of scheduling "Dial-a-Ride" transportation systems is conducted. Based upon simple mathematical models that focus on the combinatorial nature of the problem, a class of algorithms is derived for which performance can be measured in a precise asymptotic probabilistic sense. The approach yields many qualitative insights and the resulting transportation schemes have many attractive practiced features. For example, they have modest computational requirements, are decentralized, and are early to visualize and implement. [ABSTRACT FROM AUTHOR]