On the Co-Design of AV-Enabled Mobility Systems

The design of autonomous vehicles (AVs) and the design of AV-enabled mobility systems are closely coupled. Indeed, knowledge about the intended service of AVs would impact their design and deployment process, whilst insights about their technological development could significantly affect transportation management decisions. This calls for tools to study such a coupling and co-design AVs and AV-enabled mobility systems in terms of different objectives. In this paper, we instantiate a framework to address such co-design problems. In particular, we leverage the recently developed theory of co-design to frame and solve the problem of designing and deploying an intermodal Autonomous Mobility-on-Demand system, whereby AVs service travel demands jointly with public transit, in terms of fleet sizing, vehicle autonomy, and public transit service frequency. Our framework is modular and compositional, allowing one to describe the design problem as the interconnection of its individual components and to tackle it from a system-level perspective. To showcase our methodology, we present a real-world case study for Washington D.C., USA. Our work suggests that it is possible to create user-friendly optimization tools to systematically assess costs and benefits of interventions, and that such analytical techniques might gain a momentous role in policy-making in the future.Comment: 8 pages, 4 figures. Published in the Proceeding of the 23rd IEEE Intelligent Transportation Systems Conference, ITSC 2020. arXiv admin note: substantial text overlap with arXiv:1910.07714, arXiv:2008.0897

The sustainability of shared mobility: Can a platform for shared rides reduce motorized traffic in cities?

Studies in several cities indicate that ridesourcing (ride-hailing) may increase traffic and congestion, given the substitution of more sustainable modes and the addition of empty kilometers. On the other hand, there is little evidence if smartphone apps that target shared rides have any influence on reducing traffic levels. We study the effects of a shared-mobility service offered by a start-up in Mexico City, Jetty, which is used by travelers to book a shared ride in a car, van or bus. A large-scale user survey was conducted to study trip characteristics, reasons for using the platform and the general travel choices of Jetty users. We calculate travel distance per trip leg, for the current choices and for the modes that riders would have chosen if the platform was not available. We find that the effect of the platform on vehicle kilometers traveled (VKT) depends on the rate of empty kilometers introduced by the fleet of vehicles, the substitution of public versus private transport modes, the occupancy rate of Jetty vehicles and assumptions on the occupancy rate of substituted modes. Following a sensitivity analysis approach for variables with unavailable data, we estimate that shared rides in cars increase VKT (in the range of 7 to 10 km/passenger), shared vans are able to decrease VKT (around −0.2 to −1.1 km/passenger), whereas buses are estimated to increase VKT (0.4 to 1.1 km/passenger), in our preferred scenarios. These results stem from the tradeoff between the effects of the occupancy rates per vehicle (larger vehicles are shared by more people) and the attractiveness of the service for car users (shared vans attract more car drivers than buses booked through Jetty). Our findings point to the relevance of shared rides in bigger vehicles such as vans as competitors to low occupancy car services for the future of mobility in cities, and to the improvement of public transportation services through the inclusion of quality attributes as provided by new shared-mobility services

Two-step Meta-heuristic Approach for a Vehicle Assignment Problem – Case from İstanbul/Turkey

In this paper, a two-step meta-heuristic approach is proposed for vehicle assignment problem with geometric shape-based clustering and genetic algorithm. First, the geometric shape-based clustering method is used and then the solution of this method is given to the genetic algorithm as initial solution. The solution process is continued by genetic algorithm. There are 282 bus lines in İstanbul European side. Those buses should be assigned to six bus garages. The proposed method is used to determine the minimum distance between the bus lines and garages by assigning buses to garages. According to the computational results, the proposed algorithm has better clustering performance in terms of the distance from each bus-line start point to each bus garage in the cluster. The crossover rate changing method is also applied as a trial in order to improve the algorithm performance. Finally, the outputs that are generated by different crossover rates are compared with the results of the k-Nearest Neighbour algorithm to prove the effectiveness of the study.</p

Traveler satisfaction in rapid rail systems: the case of Istanbul Metro

Multi-faceted characteristics of urban travel have an impact on the passengers' overall satisfaction with the transport system. In this study, we investigate the interrelationships among traveler satisfaction, travel and traveler characteristics, and service performance in a multimodal network that comprises of a trunk line and its feeder lines. We analyze the factors influencing the choices of access to rail transit stations and the satisfaction of transit travelers with the rapid rail transit systems. We quantitatively study these relationships and demonstrate the complexity of evaluating transit service performance. Since the interrelationships among variables affecting this system are mainly stochastic, we analyze the satisfaction with transit system problem using a Bayesian Belief Network (BBN), which helps capture the causality among variables with inherent uncertainty. Using the case of Istanbul, we employ the BBN as a decision support tool for policy makers to analyze the rapid rail transit services and determine policies for improving the quality and the level of service to increase the satisfaction with transit system. In the case study, satisfaction with accessibility and access mode variables are found to be more effective variables than total travel time for travel time satisfaction, confirming the significant role of access in multimodal travels

Integrating new rail lines with existing transit services

Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Urban Studies and Planning, 2000.Includes bibliographical references (leaves 125-130).Many North American cities have recently opened or extended existing heavy and light rail systems to provide high-quality public transport alternatives. Due to the high capital and operating costs of rail transit, however, expanding the service coverage in a cost-effective manner requires more flexible and less capital-intensive supplementary modes such as buses. Integrating bus and rail services well can allow a transit system to serve a broad variety of travel needs. One recent example of a city pursuing rail transit is San Juan, Puerto Rico, where the 11-mile Tren Urbano heavy rail line is now under construction and expected to open in 2002. Tren Urbano will connect with existing bus and público (privately-operated jitney) systems. Over time, bus and pdiblico services have generally declined as the region has grown more automobile-dependent. This thesis considers the broad question of how to integrate bus and rail services successfully, focusing on the transition from a bus-only system to an intermodal system. Specifically, this thesis first develops a framework for analyzing specific integration strategies and evaluates several potential approaches a transit agency can pursue. It then discusses various planning principles that can assist decision-makers with strategic and tactical integration issues. Some of these issues include operating arrangements, fare integration, network design, and schedule coordination. To support these principles and to provide insight for the San Juan case, this research evaluates the intermodal integration experiences of five cities in the United States (Los Angeles, Miami, San Francisco, Washington, and Portland). In some cases, transit became more effective in both traditional and non-traditional travel markets when buses were used to supplement rather than compete with rail. In other cases, inattention to buses and a general lack of schedule, fare, and route coordination resulted in less favorable outcomes. Finally, this thesis applies the analytical framework, planning principles, and case study lessons to develop and evaluate strategies for integrating San Juan's existing transit network with Tren Urbano. For the buses, it focuses on evaluating service proposals for key corridors and finds that the current network structure is well-suited to feeding Tren Urbano and serving existing bus riders. For the público, it addresses more fundamental institutional issues. It explores the possibility of developing new contracted feeder small bus or van service to Tren Urbano, redirecting routes to avoid direct competition with públicos, and creating "Tren Urbano Plazas" to attract suburban motorists to transit.by Jason Lee.S.M

Concepts studies for future intracity air transportation systems

December 1970Includes bibliographical references (p. 63-66)Summary: This report is concerned with describing the possible application of future air transportation systems within urban areas of the United States. The planning horizon extends to 1995 and the report focuses on the period 1980-85 for introduction of urban air systems. The general conclusion of the study is that urban air systems will be technically and operationally feasible, but that economic viability remains inextricably linked to future governmental policies on urban development, and consequently policies for development of urban transportation. In view of the uncertainties in these policies, it becomes difficult to be definitive about the forms of future urban air systems and the research and development needs to develop these systems. The marketing section of the report identifies the kinds of urban travel markets, and attempts to apply a modal split model to show the share of the travel market which an air system would capture in competition with automobile or new forms of rapid transit. The results indicated the need for a high frequency of air service, and low values of access and egress times and costs, and reasonably competitive fares. The air system did not gain any appreciable share of the travel until trip distances were over 20 miles. Since most of the trips in an urban area are under this distance, the overall penetration of the urban travel market was less than one per cent. Application of the modal split model to data for a 1980 case study of the Boston area indicated that the loads were much too low to justify a large scale urban system. Although the modal split model results can be questioned and more work on such models is indicated, the general nature of these marketing conclusions is unlikely to change. There were two concepts for urban air systems described in this study: a "metrobus" concept which used 40-80 passenger vehicles as a public carrier in the urban area and a "metrotaxi" concept which used 4-5 passenger VTOL air taxis as a private-for-hire carrier. The components of these systems (vehicles, metroports, air traffic control system) were described as they might exist for the 1980-85 period. Appendix B describes an analysis for any public urban transportation system which demonstrates that a large number of stopping points are required of a large scale urban system in order to reduce the access and egress times and therefore the total trip time. Its conclusion is that a public urban system can never compete with a private system like the automobile for the total mass market, but must attract a much reduced travel volume consisting of trips between local areas surrounding its stopping points. This result led to access plus egress times for the air urban system on the order of 30 minutes by automobile or taxi which greatly reduced its speed advantage particularly for the shorter trips. The dominant problem in implementing an urban air system is community acceptance of the metroport, and the prime factor would be the noise of the air vehicles. A peak noise level of 85 EPndb at 500 feet is suggested as acceptable based on experience with 70 heliports in the Boston area. However, there is a need for establishing a community noise criteria based on factors other than peak noise such as frequency of service, background noise levels, number of listeners, etc. and using it to establish noise categories for metroport operation. This would give the community some assurance that the volume of noise pollution from the site can be controlled. Planning for a future urban air system is linked to planning for both future airport development and future intercity V /STOL systems. Land side congestion problems at major airports can be relieved through the provision of remote check in facilities which have an air link to the airport. The construction of new airports at sites somewhat removed from urban areas may become reasonable if urban air service exists. Similar factors affect the problems of passengers transferring from airports to metroports for intercity V/STOL service. The metroports are a ground facility common to the metrobus concept for urban air systems and intercity V/STOL, and as such link the development of these two systems.National Aeronautics and Space Administration in support of the Joint DOT/NASA Civil Aviation Polic

Strategic transit service planning in the Santurce/Old San Juan corridor

Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Civil and Environmental Engineering, 2000.Includes bibliographical references (p. 205-208).by Elton K.L. Lin.S.M

TOOLS TO SUPPORT TRANSPORTATION EMISSIONS REDUCTION EFFORTS: A MULTIFACETED APPROACH

The transportation sector is a significant contributor to current global climatic problems, one of the most prominent problems that today's society faces. In this dissertation, three complementary problems are addressed to support emissions reduction efforts by providing tools to help reduce demand for fossil fuels. The first problem addresses alternative fuel vehicle (AFV) fleet operations considering limited infrastructure availability and vehicle characteristics that contribute to emission reduction efforts by: supporting alternative fuel use and reducing carbon-intensive freight activity. A Green Vehicle Routing Problem (G-VRP) is formulated and techniques are proposed for its solution. These techniques will aid organizations with AFV fleets in overcoming difficulties that exist as a result of limited refueling infrastructure and will allow companies considering conversion to a fleet of AFVs to understand the potential impact of their decision on daily operations and costs. The second problem is aimed at supporting SOV commute trip reduction efforts through alternative transportation options. This problem contributes to emission reduction efforts by supporting reduction of carbon-intensive travel activity. Following a descriptive analysis of commuter survey data obtained from the University of Maryland, College Park campus, ordered-response models were developed to investigate the market for vanpooling. The model results show that demand for vanpooling in the role of passenger and driver have differences and the factors affecting these demands are not necessarily the same. Factors considered include: status, willingness-to-pay, distance, residential location, commuting habits, demographics and service characteristics. The third problem focuses on providing essential input data, origin-destination (OD) demand, for analysis of various strategies, to address emission reduction by helping to improve system efficiency and reducing carbon-intensive travel activity. A two-stage subarea OD demand estimation procedure is proposed to construct and update important time-dependent OD demand input for subarea analysis in an effort to overcome the computational limits of Dynamic Traffic Assignment (DTA) methodologies. The proposed method in conjunction with path-based simulation-assignment systems can provide an evolving platform for integrating operational considerations in planning models for effective decision support for agencies that are considering strategies for transportation emissions reduction