Transit Priority Research Articles

An overview of shifting cultivation with reference to Nepal

Shifting cultivation is a form of land use among resource poor communities with a rotation of cultivation and fallow in the same unit of land. Millions of indigenous people are dependent on shifting cultivation practice, with majority households for subsistence living. This practice is in transition these days with rising population of shifting cultivators and demand for more food. This paper provides a review on shifting cultivation practice in the world with reference to Nepal, with an insight on emerging land use transition, its impacts and future priorities. Key words: Shifting cultivation, biodiversity, fallow, climate change, Chepangs, Nepal.

Innovative Operating Solutions for Bus Rapid Transit through a Congested Segment of San Jose, California

The Santa Clara Valley Transportation Authority in California recently developed a strategic plan for bus rapid transit (BRT) to establish a framework for BRT implementation. Stevens Creek Boulevard, an important east-west thoroughfare linking the California cities of San Jose and Cupertino, was one of three corridors selected for BRT service. To ensure the operating and ridership objectives along the Stevens Creek corridor, BRT must maintain adequate travel speeds and provide a convenient station location along the Valley Fair segment west of downtown San Jose. Meeting these objectives would be a challenge because the segment is highly congested and right-of-way constrained. Major shopping centers, existing land uses, and an Interstate freeway interchange are all factors that contribute to the operational challenges along the Valley Fair segment. These factors also limit any roadway widening and reconfiguration required to provide sufficient space for dedicated BRT lanes and station platforms. To provide some form of transit priority and a convenient BRT station at Valley Fair, a single reversible bus lane was proposed. This paper discusses the feasibility of a single reversible lane and key elements that led to a preferred configuration and operating plan. A range of options, including various station configurations and operating strategies, is evaluated. A microsimulation analysis of the options shows that a single reversible lane can generate significant operating benefits for BRT while not significantly affecting mixed-flow traffic. This paper and its results should encourage cities to consider single-lane reversible bus ways along constrained segments as part of a strategy to implement premium BRT service.

Estimating Signalized Intersection Delays to Transit Vehicles

Many transit agencies have deployed automatic vehicle location (AVL) systems, automatic passenger counting (APC) systems, or both on a portion of their transit vehicle fleets. Data from these systems are used for realtime system monitoring and control, and archived data are often used for service performance reporting and for service planning. This paper proposes and demonstrates a method by which these archived data can be used to estimate the mean and variance of transit vehicle delays caused by signalized intersections. The proposed method is suitable for application to most transit AVL-APC databases and is demonstrated with data from Grand River Transit, the public transit service provider in the region of Waterloo, Ontario, Canada. The results obtained from the application to field data indicated that the proposed method was able to explain 96% of the variation in observed mean transit vehicle delay at signalized intersections. These results suggest that the proposed method has practical application for the identification and prioritization of candidate measures for transit priority, including transit signal priority (green extension, early green, special transit phases) and queue jump lanes.

China's Hangzhou Public Bicycle

Over the past 20 years, China has experienced a steady decline in bicycle use. To address this trend, China's central and local government for urban transportation created Public Transit Priority to encourage public transport initiatives. As part of this effort, the government of the city of Hangzhou launched Hangzhou Public Bicycle in 2008. This service allows members to access a shared fleet of bicycles. As of March 2011, Hangzhou Public Bicycle operated 60,600 bicycles with 2,416 fixed stations in eight core districts. To understand factors leading to bikesharing adoption and barriers to adoption, the authors conducted an intercept survey in Hangzhou between January and March 2010. Two separate questionnaires were issued to bikesharing members and nonmembers to identify key differences and similarities between these groups. In total, 806 surveys were completed by 666 members and 140 nonmembers. The authors found that bikesharing was capturing modal share from bus transit, walking, autos, and taxis. Approximately 30% of members had incorporated bikesharing into their most common commute. Members indicated that they most frequently used a bikesharing station closest to either home (40%) or work (40%). These modal shifts suggested that bikesharing acted as both a competitor and a complement to existing public transit. Members exhibited a higher rate of auto ownership than nonmembers. This finding suggested that bikesharing was attractive to car owners. Recommendations for improving bikesharing in Hangzhou included adding stations and real-time bike and parking availability technologies, improving bike maintenance and locking mechanisms, and extending operational hours.

Signal Strategy of Conditional Transit Priority Based on Transit Schedule

Combined with the actual situation of China, drawing on foreign models based on the quantitative methods, this paper gets a model based on conditional bus priority for signal timing design which is combined with the traditional model through the application of conditional bus priority. The model considers more about the actual situation of the intersection, as well as a variety of other general vehicles which also need to pass through the intersection; it is a more moderate, harmonious, and better public transport priority method which does not use at the expense of other general vehicles.

Optimization of transit priority in the transportation network using a decomposition methodology

A new methodology to optimize transit priority is proposed in this paper. Having a higher passenger capacity than private cars, transit vehicles can increase the passenger throughput of roads. This is the main basis for justifying the provision of exclusive transit lanes. Although a range of studies have addressed exclusive transit lanes, all have a localized focus in nominating a transit priority alternative. This paper is aimed at finding the optimum combination of exclusive transit lanes on a network basis. Transit priority is formulated as a bi-level optimization programming which considers modal split, traffic assignment, and transit assignment. A decomposition method is adapted for solving the proposed mathematical model which converges to the optimal solution. The method is also demonstrated in an example network.

Policy-Making Tool for Optimization of Transit Priority Lanes in Urban Network

Transit improvement is an effective way to relieve traffic congestion and decrease greenhouse gas emissions. Improvement can be in the form of new facilities or giving on-road priority to transit. Although construction of off-road mass transit is not always viable, giving priority to transit can be a low-cost alternative. A framework is introduced for optimization of bus priority at the network level. The framework identifies links on which a bus lane should be located. Allocation of a lane to transit vehicles would increase the utility of transit, although this can be a disadvantage to auto traffic. The approach balances the impact on all stakeholders. Automobile advocates would like to increase traffic road space, and the total travel time of users and total emissions of the network could be reduced by a stronger priority scheme. A bilevel optimization is applied that encompasses an objective function at the upper level and a mode choice, a traffic assignment, and a transit assignment model at the lower level. The proposed optimization helps transport authorities to quantify the outcomes of various strategies of transit priority. A detailed sensitivity analysis is carried out on the relative weight of each factor in the objective function. The proposed framework can also be applied in the context of high-occupancy-vehicle lanes and heavy-vehicle priority lanes.

Control Strategies for Transit Priority Based on Queue Modeling and Surrogate Testing

To explore the potential benefits of bus priority based on signal phasing strategy, this article proposes a simplified statistical sampling method to simulate vehicle delays at intersections instead of using conventional microscopic traffic simulations. This method greatly reduces the calculation cost and time while maintaining the estimation accuracy of the delay. This research provides a surrogate testing system and tests intuitive traffic signal phasing strategies that shorten average waiting time of queuing vehicles by letting certain buses pass the intersection with a higher priority. Interestingly, the results reveal that the length of the green time should be adaptive with the proportion of buses in the traffic flow. Moreover, a higher priority is suggested for the bus at certain positions in a queue so that it can pass the intersection in one green period with its preceding vehicles. The benefits of this approach include (1) reduced delay of both buses and other vehicles when the proportion of buses is small; (2) keeping the influence on network-wide traffic at a low level even when the proportion of buses is large, because the green time is only extended for a short while; and (3) ease to implement such control strategies by modifying current traffic control systems.

Calculating Model of Urban Public Transit Subsidy

Urban public transit financial subsidy is one of the key links, which promote public transit priority strategies. It is an important issue of urban traffic sustainable development to establish a specific operable subsidy calculating model and to improve the way to calculate urban public transit subsidy. This study establishes the game model among the income of residents, enterprises operating costs, and subsidies through utility theory. It shows the advantages of classification subsidy of public transit riders and establishes a specific operable subsidy calculating model. Then, the calculation of Beijing public transit subsidies in 2007 is taken as an example. The results indicate that the subsidy classification and the subsidy calculating model not only can fully satisfy the travel demands of public transit riders but also can effectively calculate the subsidy amount, which realizes the utility maximization of government subsidy. The proposed method is proved to be a new effective way to measure urban public transit subsidy.

SB 375: Promise, Compromise and the New Urban Landscape

I. INTRODUCTION II. TRANSPORTATION, LAND USE AND GLOBAL WARMING III. THE SMART GROWTH PEDIGREE: THE SLOW GROWTH MOVEMENT, AB 857 AND THE SACOG BLUEPRINT A. The Slow Growth Movement B. AB 857 C. The SACOG Blueprint IV. SB 375: STRUCTURE, IMPLEMENTATION AND THE ROLE OF CARB A. The Role of CARB B. The RTP and SCS C. The APS D. CEQA Exemptions and Streamlining i. Residential or Mixed-Use Projects Consistent With SCS/APS ii. Transit Priority Projects E. Housing Element Reform V. OBSTACLES TO IMPLEMENTATION A. Transportation Infrastructure: Smart Growth's Missing Link B. APS, Feasibility and the Breakdown of Internal Consistency C. California's Land Use Status Quo: Loose Ends, Local Ties D. California's Changing Landscape VI. RECOMMENDATIONS A. Infrastructure B. Actions by CARB i. Compliance Clarity ii. Provision of GHG Emission Evaluation Guidelines C. Consider Amendment VII. CONCLUSION I. INTRODUCTION On September 27, 2006, California Governor Arnold Schwarzenegger signed into law AB 32, (1) the Global Warming Solutions Act, widely considered the most comprehensive and progressive piece of legislation ever drafted to address the causes of anthropogenic climate change. The statute gives the California Air Resources Board (CARB) broad authority to regulate any source of greenhouse gas emissions (GHGs), including those from the transportation and land use sectors. (2) The eleventh-hour enactment of SB 375 in September, 2008 represents the first legislative step towards aligning the state's future land development with AB 32's emissions reduction goals. (3) Vaunted as a trifecta of the impossible by one of the statute's contributory drafters, (4) SB 375 seeks to harmonize three distinct areas--regional housing need, transportation infrastructure development and statewide air quality goals--in one comprehensive program. The law builds upon existing regulatory structures and seeks to incentivise compact development through a mix of project funding and process streamlining all targeted toward one end: reducing vehicle miles traveled (VMT) among California's 23 million licensed drivers. (5) Whether SB 375 will herald a new era of smart growth or simply add additional strata to an already complex planning process remains to be seen. This Comment will look to past failures and present successes to determine what potential obstacles may arise in implementing the nascent law. Additionally, the Comment provides recommendations, both legislative and administrative, intended to bridge the gap between the untested language of the statute and practical achievement of its goals. Understanding both the promise and potential pitfalls of SB 375 requires analyzing the law's overall structure to find the balance between what its language mandates and what the statute hopes to achieve through incentive--determining what must be done and what is still left to the caprice of local and regional governments. Beginning with Part II, this Comment will explore the environmental crisis and regulatory context under which the statute was conceived and ultimately enacted. The global and regional effects of climate change will also briefly be discussed. Part III will look to California's historical attempts to legislate smart growth, evaluating both the efficacy and structure of previous programs. These early state efforts to constrain suburban sprawl are presented as the evolutionary predecessors to SB 375, informing our understanding of this newest legislative species and providing an historical base from which to evaluate its potential for success or failure. Part IV provides an overview of the statute's basic functional structure. The bill is not a stand-alone law but instead amends current regional transportation and environmental statutes. …

Stochastic optimization of traffic control and transit priority settings in VISSIM

Genetic algorithms have been shown to be effective tools for optimizations of traffic signal timings. However, only one tool that combines Genetic Algorithms and traffic microsimulation has matured to a commercial deployment: Direct CORSIM optimization, a feature of TRANSYT-7F. This paper presents a genetic algorithm formulation that builds on the best of the recorded methods, by extending their capabilities. It optimizes four basic signal timing parameters and transit priority settings using VISSIM microsimulation as the evaluation environment. The program is the first optimization tool that optimizes traffic control transit priority settings on roads with both private and transit traffic. These settings are optimized either simultaneously with the basic signal timings or separately, thus improving overall traffic operations without changing existing basic signal timings. The optimization has been tested on two VISSIM models: a suburban network of 12 signalized intersections in Park City, UT, and an urban corridor with transit operations in Albany, NY. The results show that timing plans optimized by the genetic algorithm outperformed the timing plans from the field and SYNCHRO. Optimization of the transit priority settings shows that adjustment of these settings has significant impact on travelers delay on the corridors with mixed traffic and transit operations.

New Methodology for Optimizing Transit Priority at the Network Level

A new methodology for optimizing transit road space priority at the network level is proposed. Transit vehicles carry large numbers of passengers within congested road space efficiently. This aids justification of transit priority. Almost all studies that have investigated transit priority lanes focus at a link or an arterial road level, and no study has investigated road space allocation for priority from a network perspective. The aim of the proposed approach is to find the optimum combination of exclusive lanes in an existing operational transport network. Mode share is assumed variable, and an assignment is performed for both private and transit traffic. The problem is formulated by using bilevel programming, which minimizes the total travel time. The approach is applied to an example network and the results are discussed. The approach can identify the optimal combination of transit priority lanes and achieve the global optimum of the objective function. Areas for further development are discussed.

Microscopic Simulation Approach to Effectiveness Analysis of Transit Signal Priority for Bus Rapid Transit

Transit signal priority (TSP) is one of the critical components of bus rapid transit (BRT) and a key technology in enhancing its operational efficacy. It not only provides priority to the BRT vehicle but also manages the trade-off between the delay of buses at an intersection and the impacts on other traffic. This paper focuses on the design and evaluation of a simulation of signal priority for BRT under mixed traffic flow conditions. Taking the Southern Axis BRT Line 1 in Beijing as a case study, different signal priority strategies, including green extension, red truncation, and special phase insertion, are developed for the signalized intersection along the BRT route. A signal coordination plan is designed for the section composed of four intersections in the BRT system. The study uses the VISSIM microscopic traffic simulation model to analyze the impacts of traffic parameters, especially those of nonmotorized traffic, on the effectiveness of TSP along the corridor. Simulation results indicated that the BRT vehicles would typically benefit from transit priority with travel times savings and delay reduction, as well as greater schedule adherence, and suggest that these benefits may be obtained with little negative impacts to the overall system. The results also indicated that the volume of nonmotorized traffic is one of the most important factors that influence the effectiveness of TSP implementation in a mixed traffic flow.

Intermittent and Dynamic Transit Lanes

Segregated transit lanes are an efficient means of improving transit reliability and speed on shared urban roads. A major limitation of these lanes, however, is their impact on road capacity and traffic congestion. Intermittent bus lanes (IBL) are an innovative concept for addressing this limitation. IBLs include variable message signs and flashing lights embedded in the pavement that warn motorists to avoid transit lanes only when buses are coming. This approach prioritizes transit while limiting impacts on other road users. If feasible, this approach may substantially increase the scope of transit priority in cities. However, feasibility of IBL is a major concern. A trial was undertaken in Lisbon, Portugal, in 2005 and 2006. Although the results were promising, more practical experience with IBL is required to justify its widespread implementation. This paper reviews the performance of a variation on the IBL concept, the dynamic fairway (DF) adopted for trams in Melbourne, Australia. The system was initiated in 2001 and is still operational. The paper documents the world's first practical, ongoing experience with IBL-DF operation. Future plans for a Melbourne bus-based IBL called the “moving bus lane” are also presented. Overall, the performance of the Lisbon IBL trial appears to be better than that of the Melbourne DF. However, the circumstances of the two examples were different, including the road configuration, transit mode, levels of congestion, and the newness of the technologies involved. Significantly, both applications found good driver compliance with transit lanes, suggesting the IBL-DF concept has practical performance benefits.

Explicit modeling of semantics associated with composite states in UML statecharts

UML statecharts are used for describing dynamic aspects of system behavior. The work presented here extends a general Petri net-based methodology to support formal modeling of UML statecharts. The approach focuses on the specific task of generating explicit transition models associated with the hierarchical structure of statechart. We introduce a state-transition notation to serve as an intermediate model for conversion of UML statecharts, and in particular, the complexity of composite states, to other target specifications. By defining a process for deriving, from UML statecharts, a state-transition notation that can serve as an intermediate state machine model, we seek to deepen understanding of modeling practices and help bridge the gap between model development and model analysis. This work covers all of the primary issues associated with the hierarchical structure of composite states, including entry and exit transitions, transition priorities, history states, and event dispatching. Thus, the results provide an important step forward toward the goal of modeling increasingly complex semantics of UML statecharts.

Transport Policy with Public Transit Priority in Zurich, Switzerland

Transport Policy with Public Transit Priority in Zurich, Switzerland

Evaluation of Potential Transit Signal Priority Benefits along a Fixed-Time Signalized Arterial

This paper presents the findings of a study evaluating the potential benefits of implementing transit signal priority along the Columbia Pike arterial corridor, in Arlington, Va. The study uses the \IINTEGRATION\N microscopic traffic simulation model to evaluate the impact of a number of alternative priority strategies on both the prioritized buses and general traffic during the morning peak and midday traffic periods. The transit priority strategies considered include providing priority to express buses traveling along Columbia Pike, to both express and regular buses along the arterial, and to all buses within the study corridor. The priority logic that is considered in the study provides simple green extensions and green recalls within a fixed-time traffic signal control environment. The simulation results indicate that the buses provided with priority would typically benefit from transit priority, but that these benefits may be obtained at the expense of the overall traffic, particularly when traffic demand is high. However, it is also found that in periods of lesser demand, the overall negative impacts could be negligible due to the availability of spare capacity at the signalized intersections.

Integrated Transit Priority and Rail/Emergency Preemption in Real-Time Traffic Adaptive Signal Control

The article discusses a strategy, referred to as Categorized Arrivals-based Phase Reoptimization at Intersections (CAPRI), which integrates transit signal priority and rail/emergency preemption within a dynamic programming-based real-time traffic adaptive signal control system. The system takes as input sensor data, from detectors, automatic vehicle locators, transponders, etc., for real-time predictions of traffic flow, and “optimally” controls the flow through the network using signal phasing. The system utilizes a traffic adaptive signal control architecture that (1) decomposes the traffic control problem into several subproblems that are interconnected in a hierarchical fashion, (2) predicts traffic flows, at appropriate resolution levels (individual vehicles, platoons of vehicles, transit vehicles, emergency response units, and trains) to enable proactive control, (3) supports various optimization modules for solving the hierarchical subproblems, and (4) utilizes data structure and computer/communication approaches that allow for fast solution of the subproblems, so that each decision can be implemented in the field within an appropriate rolling time horizon of the corresponding subproblem. Simulation-based analyses illustrate the effectiveness of the CAPRI system.

Hardware-in-the-loop simulation

The current generation of macroscopic and microscopic simulation packages do not have control algorithms that incorporate many of the advanced features now available in commercial traffic control hardware. Consequently, there is a need to develop cost effective procedures for evaluating state of the practice traffic signal control equipment so that informed deployment and design decisions can be made. These same procedures can also be used by researchers to develop new algorithms for applications such as transit priority or adaptive control. In order to achieve that objective, this paper presents the motivation for using hardware-in-the-loop simulation procedures. Hardware-in-the-loop simulation presents a new set of challenges for traffic engineering model developers as the “correctness” of a real-time model not only depends upon the numerical computation, but the timeliness with which the simulation model interacts with external control equipment. This paper reviews the state of practice, summarizes the fundamental technologies necessary for implementing such a system, and uses a simple statistical test for assessing the real-time errors introduced into a simulation model.

Assessment of streetcar transit priority options using microsimulation modelling

The thrust of a recently published transportation vision for Toronto is focused largely on reducing automobile dependence via a number of interacting strategies, including the wide application of transit priority policies to improve transit competitiveness. This paper reports on quantifying the impacts of several transit priority schemes, with the streetcar operation along King Street in the heart of Toronto as a case study. Four scenarios were modelled in a micro simulation framework. They include the status quo (involving unconditional transit signal priority, already in operation), turning off existing transit signal priority, prohibiting all left turns, and finally prohibiting traffic from King Street. To quantify the impacts of any of the above scenarios, a set of common measures of effectiveness was used, including transit travel time and speed, effective headway, service frequency and person throughput, bunching, fleet size implications, and overall traffic and transit average speeds. The results show the relative merits of the four scenarios and two strategies for improving streetcar service along the King route are recommended. The first is to prohibit all left turns along the route, while the second, admittedly more aggressive, is to potentially transform the arterial into a transit mall accessible only to streetcars.Key words: transit signal priority, transit priority, signal control, microsimulation, streetcars.