Control of personal rapid transit systems

The problem of precise longitudinal control of vehicles so that they follow predetermined time-varying speeds and positions has been solved. To control vehicles to the required close headway of at least 0.5 sec, the control philosophy is different from but no less rigorous than that of railroad practice. The preferred control strategy is one that could be called an “asynchronous point follower.” Such a strategy requires no clock synchronization, is flexible in all unusual conditions, permits the maximum possible throughput, requires a minimum of maneuvering and uses a minimum of software. Since wayside zone controllers have in their memory exactly the same maneuver equations as the on-board computers, accurate safety monitoring is practical. The paper discusses the functions of vehicle control; the control of station, merge, and diverge zones; and central control.     

Safe design of personal rapid transit systems

The safety of personal rapid transit systems involves careful attention to all features of the design such as the use of a hierarchy of fault-tolerant redundant control systems, bi-stable fail-safe switching, back-up power supplies, vehicle and passenger protection, and attention to the interaction of people with the system. Safety, together with reliability and adequate capacity, must be achieved while making the system economically attractive, hence techniques to achieve these goals at minimum life-cycle cost are primary in PRT design. Building on theory of safe, reliable, environmentally acceptable, and cost-effective design of PRT systems developed during the 1970′s, in 1981 the author and his colleagues initiated design of a new PRT system, now called Taxi 2000. The paper describes the relevant features of Taxi 2000 and principles of safe design incorporated into it.     

A note on fare policy in personal rapid transit

The choice of fare policy is more flexible in personal rapid transit than in conventional transit and has some unique aspects. The implementation of fare policies as a function of distance are discussed, and, following a discussion of how the fare would be collected in a PRT system, consideration is given to whether the fare should be per person or per vehicle.     

Synchronous or clear-path control in personal rapid transit systems

This note derives an equation for the ratio of the maximum possible station flow to average line flow in a personal rapid transit or dual-mode system using fully synchronous control. It is shown that such a system is impractical except in very small networks.     

Designing personal rapid transit (PRT) networks

This paper presents a heuristic method for designing a PRT network. Because the PRT system operating characteristics and performance measures differ widely from those of conventional transit technologies, an algorithm for the PRT network design problem (NDP) is derived by using concepts from some current NDP algorithms. We minimize the sum of passenger travel time cost, construction cost, vehicle cost and operational costs, subject to an available budget of guideway, a maximum number of vehicles and given link capacities. Starting with a well-connected initial network, the algorithm eliminates and adds links iteratively as it searches for a near-optimal solution. If this solution satisfies the budget constraint, it is considered to be acceptable. Otherwise, additional links are deleted until a feasible near-optimal solution is obtained. The link elimination phase of the algorithm only considers half of the links at a time which greatly decreases computing time. None of the links in an acceptable solution will be overloaded.     

A review of the state of the art of personal rapid transit

The paper begins with a review of the rational for development of personal rapid transit, the reasons it has taken so long to develop, and the process needed to develop it. Next I show how the PRT concept can be derived from a system‐significant equation for life‐cycle cost per passenger‐mile as the system that minimizes this quantity. In the bulk of the paper I discuss the state‐of‐the‐art of a series of technical issues that had to be resolved during the development of an optimum PRT design. These include capacity, switching, the issue of hanging vs. supported vehicles, guideways, vehicles, control, station operations, system operations, reliability, availability, dependability, safety, the calculation of curved guideways, operational simulation, power and energy. The paper concludes with a listing of the implications for a city that deploys an optimized PRT system.     

Dependability as a measure of on-time performance of personal rapid transit systems

A comprehensive method for calculating and measuring Dependability of Personal Rapid Transit systems is derived and compared with the more common measure called Availability. Availability is the percentage of all revenue trips that are completed without interruption. It does not take into account the duration of delays of the passengers because of the diffiiculty of gathering the necessary information in conventional transit systems. In PRT systems, vehicle-hours of travel and of delay relate in a statistically simple way to person-hours of travel and of delay. Therefore, in such systems, it is practical to use the performance measure called Dependability that takes into account the inconveince of people as a result of delays. To form a bridge to present practice, it is recommended that both measures be calculated and compared in forthcoming PRT systems. With today's computer systems, this is easily accomplished.     

Built environment and pedestrian behavior at rail rapid transit stations in Bangkok

Urbanization and demands for mobility have spurred the development of mass rapid transit infrastructure in industrializing Asia. Differences between the character of pre-existing urban structure in these localities and worldwide precedents suggest a need for studies examining how new rapid transit systems function locally. This study of Bangkok’s elevated and underground rail systems identifies relationships between the built environment and pedestrian behavior surrounding stations. Based on details of 1,520 pedestrian egress trips from three elevated and three underground stations in 2006, multiple regression and analysis of variance (ANOVA) revealed that types of pedestrian destinations, reflecting land uses, were related to length of walking egress trips. Trips to shopping centers and office buildings were longer, while trips to eating places were shorter. The most common type of pedestrian trip recorded was to another vehicle, and trips to automobile taxis and motorcycle taxis figured prominently. Policy implications of the findings are considered.     

An analysis of the 1968 rapid transit vote in Los Angeles

Analysis of the results of past mass transit bond issues can aid transportation planners in understanding and anticipating voter behavior. This paper reports the results of an analysis of the 1968 rapid transit bond issue vote in Los Angeles, California. The simple relationships of the vote to a variety of possible explanatory variables are first examined. An attempt to assess the relative independent importance of these variables and to offer a partial explanation of the vote using multiple regression analysis is then presented. Variables found to have had the greatest impact on the vote are proximity to the proposed transit system, income-level, and ethnicity. Variables found to have had little or no effect, on the other hand, are population density, age, partisanship, and election turnout rate. The analysis indicates that the frequently used mood-of-the-electorate explanation of bond-issue failures in general, and transit proposals in particular, underestimates the quality of the electoral decision. The electorate does make rational distinctions, and future bonding attempts will confront voters capable of perceiving the utility to them of proposed transit systems and voting accordingly. The policy implications of this analysis suggest that the design of future mass transit proposals should, firstly more explicitly attempt to incorporate the preferences of middle-income voters, and secondly, be part of a comprehensive transit plan for the entire metropolitan area.     

Optimization of emergency crossovers and signals for emergency operations in rail rapid transit

This paper presents a methodology for designing rail transit systems to meet operating requirements when track maintenance or failure cause sections of tracks to be unavailable for service. The methodology can be also used to establish the requirements for the continuity of operations during construction. The main objective of the paper is to develop a tool which performs trade-offs between system costs and level of services during emergencies/construction. Several alternatives, including various signal and control systems, number and types of crossovers and corresponding operating strategies, are developed and evaluated against capital investments. Operating measures and strategies for the selected alternative can be recommended before the design phase is completed, because the designer, by using this methodology, is aware of the capacities attained during emergencies and construction.     

A causal analysis of car ownership and transit use

The causal structure underlying household mobility is examined in this study using a sample obtained from the Dutch National Mobility Panel survey. The results indicate that car ownership is strongly associated with mode use, but that it has no influence on weekly person trip generation by household members. Characteristics of mode use are examined through a causal analysis of changes in car ownership, number of drivers, number of car trips, and number of transit trips. It is shown that observed changes in mode use cannot be adequately explained by assuming that a change in transit use influences car use. The finding suggests that the increase in car use, which is a consequence of increasing car ownership, may not be suppressed by improving public transit.     

The importance of attitudes in the decision to use mass transit

This paper reports the results of tests of the hypotheses that attitudinal variables are important in mode choice decisions and that they can significantly increase the explanatory power of network-based mode choice models. Conflicts between the results of previous work by Lovelock and Johnson are resolved by this study. Attitudinal items used by Johnson and by Lovelock in separate studies in the San Francisco Bay area were included in a survey of Chapel Hill households. Tests of the incremental explanatory power of the attitudinal variables in mode choice models confirm that the items used by Johnson do not contribute to the explanatory power of models using network time and cost data. Similar tests showed that Lovelock's attitudinal items do significantly increase the predictive ability of the models. The conflicting results of these previous studies are therefore due to the content of the items. Attitudinal data, including both attitude items and measures of perceptions of system attributes, do enhance the predictive power of models involving network data.This research was supported by a grant from the Urban Mass Transportation Administration, U.S. Department of Transportation, Washington, D.C.     

Choosing the wrong technology: Or how to spend billions and reduce transit use

In spite of a broad consensus among transportation analysts that bus rapid transit, whether operating on exclusive rights-of-way or on uncongested high occupancy vehicle lanes or general purpose limited access facilities, provides higher performance and has significantly lower costs per passenger trip than rail transit in medium and low density cities, nearly all Sunbelt cities are building or planning heavy or light rail systems. This paper reviews previous studies of the cost-effectiveness of heavy and light rail transit with bus-rapid transit and the growing experience with busways and transitways and concludes, once again, that some form of bus rapid transit would be a far more effective way of providing improved transit in these cities than heavy or light rail transit. Not only would bus rapid transit be substantially cheaper, but it would provide a higher quality of service than light or heavy rail transit for virtually all users. Finally, the paper speculates on the reasons for the continued, “blind” commitment to rail transit by policymakers in Sunbelt cities and on the refusal of policymakers in all but a few of these cities to even consider bus rapid transit.     

Grouping travelers on the basis of their different car and transit levels of use

Market segmentation studies in travel behavior research are ordinarily based on socioeconomic characteristics and personality traits. This study explores the usefulness of a different approach, where the actual overall mobility levels across different ground transportation modes, along with desired changes in the use of cars and transit, are used as clustering variables. Using a given mode can in fact influence the personal representation of that mode, which in turn has been proven to be a key element in transport behaviours. We form such multimodality-based clusters from two field studies, one involving employees of the French transportation research institute INRETS and the other a representative sample of residents of the US San Francisco Bay Area. We find that strong users of a given mode would like to bring more balance to their “modal consumptions” by decreasing the use of this mode more than the average, and increasing the use of the alternative mode. However, concerning ground transport travel budgets, the desire to travel more (or less) overall seems less strongly related to the composition of the modal balance. The US dataset shows also a greater latent demand for travel than the French one. Socioeconomic characteristics of the clusters could not explain the patterns that were found, confirming the importance of taking into account multimodality issues in travel behavior research. Some policy implications from these findings are finally reported.

Energy use reduction potential of passenger transport in Europe

To contribute to a sustainable society, considerable reduction in energy use and CO₂ emissions should be achieved. This paper presents the results of calculations exploring the energy use reduction potential of passenger transport for Western Europe (OECD Europe minus Turkey). For these calculations, three types of options are defined emphasizing technological, infrastructural and behavioural change. By 2050, technological improvements may reduce energy use per passenger-km by - 30%. Adding infrastructural options, an energy reduction of > 50% by 2050 can be realised. To achieve further energy reductions, options with a large behavioural impact should also be implemented. This results in an 80% energy reduction potential in the transport sector by 2050. To calculate the reduction potential on OECD Europe level, one should factor in expectations concerning mobility growth. Two mobility development scenarios are used. Both scenarios foresee a net decrease in total energy use of 20% with the introduction of the technological and infrastructural improvement options. Adding options emphasizing behavioural change results in a net reduction potential of - 60% by 2050.     

The impact of rail transit on land use: Evidence and a change of perspective

On the basis of available evidence we cannot clearly establish a causal relationship between rail transit and changes in land use and development patterns. At best, such changes would seem to occur only in the presence of other favorable factors, such as supportive local land use policies and development incentives, availability of developable land and a good investment climate. In any event, however, determining the precise extent of rail investment's effect on urban structure is less important than assessing the role it could play in an overall strategy for reaching larger urban goals.     

Automated transit and land use intentions: Alternate scenarios with PRT and shuttle/loop technologies

Ecological impacts of urban sprawl on the land, as well as forces that engender sprawl are outlined. Long-range land use priorities for more compact, transit-oriented development (TOD) are seen as ecological imperatives. While Personal Rapid Transit (PRT) could solve some congestion, it does not address these priorities. Several assumptions that underlie the PRT concept, particularly the premise that denser land use is per se socially undesirable, are challenged in terms of historical precedent. Rather, the explosive scale of ubiquitous motoring is seen as the key component of today's resistance to dense development. With peripheral parking and medium-capacity AGT links to regional transportation networks, new TOD could be redefined as pedestrian-zoned and richly landscaped urban neighborhoods; this would help resolve essential traffic and environmental barriers to its realization. The simpler automated shuttle and loop technologies are seen as more compact and potentially affordable for this purpose. Steps that could help open the way toward realization of such development are discussed.     

Use of ensemble averaging and differential comparison to detect retail sales increases by the bay area rapid transit system

A method based on ensemble averaging and differential comparison is used to enhance and isolate retail sales variations by the Bay Area Rapid Transit system in metropolitan San Francisco. A sales difference function, related to transit system operation, is shown to exist at a Gaussian probability level near 0.95.