Tram Operation Research Articles

Curve squeal of modern tramcars: comparison between independently rotating wheels and solid axles

ABSTRACT Curve squeal noise is still one of the most serious problems related to the operation of trams in urban networks. Several mitigation solutions have been proposed in past research, usually dealing with friction modifiers or damping elements installed on the wheels or on the rails. In this paper, the role of the bogie architecture on curve squeal occurrence is investigated. Vehicle dynamics simulations and a wheel/rail coupled model in the frequency domain are used to compare curve squeal predictions in case of Independently Rotating Wheels (IRW) and Solid Axles (SA). The SA configuration results in higher longitudinal creepage compared to IRW. This modifies the transverse creep curve, making this design solution less susceptible to curve squeal induced by falling friction. Despite the well-known improved curving behaviour in sharp curves, the IRW architecture has been found to be more prone to curve squeal compared to the SA tramcar.

Shaping light rail vehicle wheel profile in terms of wear and ride safety

This paper presents relationships between tram wheel profile geometry and ride safety and wear factors in a model based approach. In order to properly formulate the assumptions for the wheel profile geometry, the influence of selected parameters of the tram wheel profile (number of contact points, clearance between the wheel and the rail, flange inclination) on the dynamic interaction with the rail was determined. Referring to the current state of tram operation conditions in Polish cities, as well as the available scientific literature, the existing, incorrectly selected wheel-rail pairs were also identified in terms of unfavourable placement of contact points, similarity of profile shapes and clearance between the wheel and rail. The interdependencies presented in this work complement the knowledge in the field of cooperation of the tram wheel with the rail, as well as shaping the wheel profile, which is particularly valuable due to the limited number of scientific studies on this subject so far.

Enhancing Tram Safety in Mixed-Traffic Systems: A Case Study of Melbournes Tram Collision Factors and Improvement Strategies

Abstract: Trams, a vital component of public transportation, operate within diverse environments ranging from fully segregated tracks to mixed-traffic systems. This study investigated tram collisions in Melbournea city renowned for its extensive and historic tram networkand explored both systemic and behavioral factors contributing to these incidents. The analysis identified key factors such as the arrangement of tram platforms, intersection design, right-of-way (ROW) regulations, tram driver behavior, and the actions of other road users. The study revealed that inadequate tram platform arrangements and suboptimal intersection designs are major contributors to tram collisions. Recommendations for improvement include implementing elevated, standalone tram platforms with protective barriers and accessible ramps, expanding the use of Hook Turn intersections, and integrating intelligent transportation systems to enhance traffic management. Additionally, addressing behavioral factors is crucial. Enhanced training for tram drivers and educational campaigns for pedestrians and other road users are proposed to improve situational awareness and adherence to safety norms. By addressing both objective systemic issues and subjective behavioral factors, this study aimed to enhance the safety of tram operations in mixed-traffic environments, ultimately reducing collision risks and improving public confidence in tram systems.

Robustness-Based Approach for Slack Time Optimization in Tram Timetables

AbstractConsidering the unique interplay of trams with road traffic, this study explored the issue of instability in tram operations—a prominent medium-capacity rail transit. Our goal was to design a timetable slack time optimization method for scheduling slack time to improve the stability of tram operations. To facilitate this, we derived the travel/dwelling time distribution from historical data, which assisted in estimating interference times and evaluating the requisite slack time. We then developed an integer programming model to calculate both the punctuality rate and expected delay under varying travel times, enabling the creation of alternative slack time schemes. Using a unique tram operation simulation logic, we assessed the operational efficiency and reliability of these alternate schemes based on specific operational indicators. The results suggest that our novel approach to timetable optimization significantly enhances the tram’s adaptability to disruptions, directly improving the passenger experience and tram competitiveness. This work offers a robust framework for timetable optimization for semi-independent right-of-way public transportation.

Multi-objective online driving strategy optimization for energy storage tram considering battery life

Compared with the traditional overhead contact grid or third-rail power supply, energy storage trams equipped with lithium batteries have been developed rapidly because of their advantages of flexible railway laying and high regenerative braking energy utilization. However, trams may face expensive battery replacement costs due to battery degradation. Therefore, this paper proposes a multi-objective optimization method for the tram's driving strategy to reduce operational energy consumption and extend battery life. The method describes the optimization problem as second-order cone programming (SOCP). It uses the interior point algorithm for fast solving, thus obtaining the theoretical optimal speed trajectory in real-time. This feature enables the method to be applied online. To verify the effectiveness and robustness of the proposed method, we conducted simulations under actual operating conditions. The simulation results show that the proposed multi-objective optimization method can extend the battery life by 40 % compared to the single-objective optimization method for energy saving. As a result, the total cost of the whole life cycle is reduced by 6.54 %. Furthermore, this online optimization driving strategy method can effectively deal with unexpected conditions during the actual operation of the tram to ensure the secure operation, punctual arrival, and precise parking of trams. Finally, the effectiveness of the proposed method is further verified by a hardware-in-the-loop (HIL) test.

Целесообразность применения цифровых трамваев на шинах в городах России

Objective: show the prospects of using an innovative type of public urban transport - a digital tram on tires with optical guidance along a strip marked on the road or using magnetic markers along the route, as attractive to passengers, cheaper in the arrangement of lines, as well as requiring less time to build than rail tram for urban transportation, allowing to relieve city roads from traffic jams and improve their ecology. Methods: an analysis and generalization of the operating experience of new digital trams built by the Chinese company CRRC, operated in the cities of China: Zhuzhou, Yibin, Yongxiu, Yancheng and Shanghai, as well as the most advanced designs of the operating rolling stock. Results: the operation of the tire tram revealed a number of problems: after a year of operation, severe rutting appeared on a dedicated lane of the road, speeds and capacity were lower than declared. The construction of new tire tram lines required costs for strengthening the roadway, which was not originally intended by the manufacturer. The possibility of their use in winter climate conditions on roads covered with ice and snow has not been proven. Further testing is required to identify and eliminate emerging deficiencies. Practical significance: despite a number of identified shortcomings, it is advisable to use a digital tire tram for cities with a warm climate, with complex terrain and narrow streets as a medium-capacity vehicle that can improve the mobility and quality of life of citizens, as well as reduce the negative impact on the environment. It is advisable to lay it in new residential areas and industrial zones under construction, as well as to use it for mass transportation of passengers in the event of any major one-time events: major exhibitions, forums, Olympic Games, world football championships, etc.

Capped Robust Optimal Control Method to Improve Tram Operation Reliability Considering Random Number of Passengers at Station Serving Multiple Lines

Tram signal priority control is a crucial approach for enhancing the reliability of tram operations and has been implemented in various cities. Nevertheless, unpredictable tram operations influenced by tram dwell time during station stops can cause signal priority control failure at intersections. It is challenging to precisely predict tram dwell time at stations that offer multiple lines. To address this issue, the proposed research presents a capped robust optimal control (CRC) technique for tram signal priority. This method entails considering the stochastic number of passengers boarding and alighting at stations with multiple lines. Furthermore, tram delay calculation models at intersections are established and integrated into an objective function. The main objective of this strategy is to enhance tram operation reliability and maximise tram operation efficiency while reducing the adverse impact of tram priority on other vehicles at the intersection. A case study was conducted to evaluate the effectiveness of the CRC method. The results indicate that the CRC technique significantly improves tram operation reliability and efficiency.

Self-adaptive rail edge detection for trams based on mathematical morphology.

With the growing number of tram operation lines, tram-related traffic incidents, particularly train collisions, have become a major issue. Therefore, the ability to identify foreign objects on a track is critical to tram operational safety. Accurately identifying the rail edge is a critical technology for recognizing the track area and providing early warnings of potential threats. Therefore, this study proposes a self-adaptive rail-edge detection algorithm that uses mathematical morphology and computer vision technology to accurately extract rail edges. The performance of the proposed algorithm was compared to that of existing algorithms, including the Canny algorithm and two other methods described in publication. Three scenes in the level crossing area of trams were considered as the research objects, and the effects of two types of noise in the image were explored in terms of the investigated using mean square error (MSE), peak signal-to-noise ratio (PSNR), and computational time. The results showed that the proposed model exhibited strong robustness for different scenes, particularly in the presence of noise. This suggests that the proposed algorithm could be used in early warning systems of trams to identify rail edges.

Improving the efficiency of route passenger transport systems by using recovered energy

This article analyzes the problems associated with increasing the efficiency of route passenger transport systems, with an in-depth consideration of tram subsystems. The focus is on using recovered electrical energy to optimize the operation of trams. The recovered energy produced during vehicle braking or deceleration can be effectively stored in on-board storage devices and then used to power the tram's traction system. The article makes the case for the relevance of this proposal, emphasizing not only the potential benefits in efficiency and resource savings, but also its significance in terms of reducing emissions and environmental sustainability of the public transport system. Schemes for implementing this approach are presented, including technical aspects of implementation and possible algorithms for controlling the energy storage and distribution system. An important element of the analysis is to determine the expected economic effect from the implementation of the proposed system. The authors of the article present an assessment of the economic benefits that can be achieved by reducing energy costs for traction and reducing the costs of maintaining and operating the transport system. Potential investments and financial aspects of implementing a new system are also discussed, which makes this study interesting both for engineers and technical specialists, as well as for economists and managers in the field of transport infrastructure.

As Safe Figures, Leaders Encourage a Focus on Work Performance in Tram Drivers

The study aimed to verify the prediction of general work performance by a perception of a leader as a security provider (LSP) in tram drivers. Contextual performance (job dedication) was a mediator in the predictive model. The research sample consisted of 196 tram drivers, 62.22% of the organization’s tram drivers. All participants shared the same leader, the head of the tram operation. They completed quantitative cross-sectional self-administered surveys. Results showed that job dedication (contextual performance) predicted the general performance. Job dedication as a partial mediator enhanced the percentage of the general performance’s explained score from 15.3% to 26.3%—predicted by perceiving the leader as a safe figure. Discussion suggested further analyzing the functions of a leader as an attachment figure in work settings and their connections to the other organizational behavioral variables. Functions of emotionality and separation distress did not relate to the work performance of tram drivers. Secure-based leadership and focus on job dedication fostered the tram drivers’ general work performance.

Simulation of the impact of tram operations on road network performances

The City government of Semarang has a plan to build a tram way in Semarang Old City Area as a public transportation mode to accommodate tourism activities. The existence of tram way can impact the performance of existing road network due to being built on existing roads side by side with other vehicles. Street network performances discussed in this paper are on the vehicle-kilometres travelled (VKT), and vehicle-hours travelled (VHT), to determine the aforementioned changes, traffic simulation was done with PTV VISSIM software. Vehicle-kilometres travelled decreased by 12,76%, vehicle-hours travelled increased by 10,54%. To minimize the impacts, two mitigation scenarios are simulated, mitigation 1 which is one-way system and mitigation 2 the combination of one-way system and signal optimizations. In mitigation scenario 1 the value of VKT decreased by 13,12%, VHT decreased by 0,65% compared to existing conditions. In mitigation scenario 2 the value of VKT decreased by 17,54%, VHT decreased by 4,93%.

The Man with a Million Names: A Personal Essay on Transit Work

This essay is a scholarly personal narrative about transit work, especially the operation of omnibuses, horse cars, trolleys, and trams in New York City in the nineteenth century. The culminating event is the trolley strike of 1895, the longest in New York history, and the theme is the need for solidarity between transit workers and the riding public, and thus for what is now is called union “Bargaining for the Public Good.” In this essay, the author speaks as both a transit worker and an historian.

“Braking bad”: The influence of haptic feedback and tram driver experience on emergency braking performance

Trams are experiencing a resurgence with worldwide network expansion driven by the need for sustainable and efficient cities. Trams often operate in shared or mixed-traffic environments, which raise safety concerns, particularly in hazardous situations. This paper adopts an international, mixed-methods approach, conducted through two interconnected studies in Melbourne (Australia) and Birmingham (UK). The first study involved qualitative interviews, while the second was an experimental study involving a virtual reality (VR) simulator and haptic master controller (i.e., speed lever). In tram operations, master controllers play a critical role in ensuring a smooth ride, which directly influences passenger safety and comfort. The objective was to understand how a master control system, enhanced with additional haptic feedback, could improve tram driver braking performance and perceptions in safety-critical scenarios. Interview results indicate that the use of the emergency brake is considered the final or ultimate choice by drivers, and their driving experience is a moderating factor in limiting its application. Combined with the experimental results, this paper highlights how implementing haptic feedback within a master controller can reduce the performance disparity between novice and experienced tram drivers.

Powered modernity, contested space: literary modernism and the London tram

ABSTRACT A literary history of London’s tramways spans the period between late-Victorian and High Modernism, encompassing naturalist fiction, reportage, creative non-fiction, modernist poetry, and the psychological novel. The same timespan saw the horse tram give way to the electric tram, which itself faced replacement by motor buses and trolleybuses during the 1930s. This essay intersects these two narratives, of literary history and of transport history, as a contribution to mobility humanities focused on the city. Trams and tramways had a peculiarly in-between identity as vehicles and environments emerging from powered modernity but associated with the proletariat, as well as the urban districts where they lived. Reading literary texts by Arthur Morrison, Ford Madox Ford, and Virginia Woolf, spotlighted here as part of a broader corpus extending from the 1880s to the 1980s, brings the tramways’ interstitiality to life. Trams, the literary readings demonstrate, were a contact zone that threatened to overturn separations of class and gender, as well as presaging an expanded future in which the city would be built around the industrial working class. The curtailment of tram operations in 1930s London meant that such a future never came to pass, but literary texts are windows onto its possibility.

Energy-efficient predictive control for trams incorporating disjunctive time constraints from traffic lights

Tram operations are often blocked by traffic lights, leading to frequent decelerations and re-accelerations that increase operational energy consumption. This paper focuses on tram energy-efficient control problem incorporating time constraints from traffic lights that have multiple feasible green time windows (GTWs). We formulate the problem as a mixed-integer nonlinear program (MINLP), where binary variables are assigned to model disjunctive time constraints of the GTWs. To address computational challenge of solving the MINLP, we reformulate it as a tractable nonlinear program (NLP). Specifically, an equivalent NLP is first presented by replacing the integrality constraint with nonlinear constraints, and then the nonlinear constraints are relaxed and penalized into cost functions. To recover a solution of the MINLP, we propose a computationally efficient sequential quadratic programming algorithm in a shrinking horizon model predictive control framework, which updates the penalty parameter and quadratic programming subproblems in parallel. The solution obtained from the subproblem is feasible in each iteration, and convergence of the feasibility iterations can be enforced by the updated penalty. The performance of the proposed approach is investigated on different scenarios using real-life tram data. Results show that the method is able to generate energy-efficient driving trajectories in a dynamic environment, while crossing traffic lights in effective GTWs without unnecessary decelerations and re-accelerations.

An adaptive backstepping nonsingular fast terminal sliding-mode control for the electromechanical brake system with backlash nonlinearity compensation

With the operation of low-floor trams, unavoidable nonlinear factors such as backlash and parameter perturbation are present in electromechanical brake (EMB) systems. This results in poor clamping force tracking performance and challenges the operational safety of trams. Thus, an adaptive nonsingular fast terminal sliding-mode control algorithm is proposed to address this thorny problem. Firstly, a differentiable function approximates the backlash nonlinearity. Then, a dynamic mathematical model for an EMB system with backlash nonlinearity and parameter perturbation is established. Based on the backstepping control principle, this paper divides the system into three subsystems, and the nonsingular fast terminal sliding-mode control (NFTSMC) algorithm is adopted to design the controller of each subsystem. Notably, the NFTSMC algorithm can solve the parameters perturbation problem by the large switching gains, which may cause the chattering phenomenon. This paper utilizes the adaptive law to establish an adaptive NFTSMC algorithm to improve this phenomenon. Furthermore, the global asymptotic stability of the system is analyzed using Lyapunov theory. Finally, experimental results clearly validate the effectiveness and superiorities of the proposed control algorithm.

Numerical Simulation Research on Mechanical Optimization of a Novel Fastener Type Ballastless Track (NFTBT) for Tram

In view of the problems present in the construction process of the embedded track structure of modern tram, we have designed a Novel Fastener Type Ballastless Track (NFTBT) for tram. To optimize the size of the NFTBT’s structure, the finite element model of the NFTBT’s structure in the tram running stage is built, the mechanical characteristics of the NFTBT’s structure are calculated, and the geometric parameters of the NFTBT’s structure are systematically studied. The research results are as follows: (1) As the size of the track slab increases, the displacement differences of the middle part of the NFTBT are similar, and the size of the track slab has little effect on the displacement. (2) The stress difference of the NFTBT’s structure under the different distances between the centers of the adjacent grouting holes’ conditions is small. Although a larger distance between the centers of the adjacent grouting holes can reduce the number of grouting holes in the track slab, the distance should not be too large to reduce the peak stress at the bottom of the NFTBT. (3) When the distance between the adjacent fasteners of the NFTBT changes within a certain range, the rail is greatly affected by the uneven settlement of the subgrade, and the track irregularity will be aggravated. (4) The NFTBT does not require the implementation of cable passages at intervals, which facilitates the passage and fixation of the cables in the tram operation section and can reduce the difficulty of adjusting the geometry of the track structure, thus accelerating the construction progress.

Technical Comparison of Commercially Available Trams and Review of Standardization Frame and Design Principles

Tram manufacturers have different ways of approaching the design of low-floor trams with compact and reliable running gears, and therefore several tram architectures can still be found. A complete standardization of trams is nearly impossible, and technical innovations can be more easily introduced if compared to conventional railway vehicles, but the trend towards large-scale standardization based on vehicle “platforms” can be seen in recent years. However, the current “standard” tram architecture, which includes only non-pivoting bogies, is not able to solve some typical problems of tram operations, such as high wheel and rail wear and high-pitched tonal noise (squeal) in sharp curves, which are described in the present paper. This research analyses the tram market with the aim of describing the state of the art of currently available products and comparing their main technical parameters. The analysis is based on information available from the literatures (journals, web) where data about the vehicles can be found, while a new designation code (tram architecture designation, TAD for short) is specifically introduced for easier identification of the different tram architectures. Even if the complete low floor is still one of the main requested features, several solutions combining pivoting and non-pivoting bogies are commercially available, showing a tendency to give more relevance to running quality performance with respect to the recent past.

Reintroduction in the Process of Operation of Worn Metal Assemblies, from the Composition of Public Transport Vehicles, Using Mechanized MIG/MAG (GMA) Welding Reconditioning, in Conditions of Guaranteeing Traffic Safety

Replacing worn or damaged parts implies high material costs and financial expense for public tram transportation services, especially for the imported units and that is why it is preferable to recondition them, taking into consideration the safety requirements. In this paper, ISIM initiatives and achievements are presented in the field of cost reduction and maintenance during operation of trams, by introduction in the operation process of worn parts, within the safety limits. Aspects are presented regarding the possibilities for reconditioning and repair of parts with a circular geometry (e.g. wheel bands, axles, drum brakes). Some of these are being applied and implemented. Also, innovative ideas are presented for increasing the performance of equipment used for reconditioning.

Online extremum seeking-based optimized energy management strategy for hybrid electric tram considering fuel cell degradation

In order to realize optimal power distribution between proton exchange membrane fuel cell and supercapacitor in hybrid electric tram, an online extremum seeking-based optimized energy management strategy is proposed in this work. Considering that the fuel cell is a complex nonlinear system, its performance will vary as the external parameters change, so it is necessary to consider the performance state of stack. An online extremum seeking algorithm is investigated in this work to seek the maximum power and maximum efficiency points by searching the variation in fuel cell performance. Besides, this work also updates its “safe operating zone” based on the results of the online extremum seeking. This process is achieved by the adaptive recursive least square algorithm. Furthermore, in order to limit the power dynamic of fuel cell, the degradation of the stack is considered in this study. To guarantee the stable and continued operation of the electric tram, the state of charge fluctuation range of supercapacitor is also limited. The effectiveness of the presented method is successfully verified under scaled-down operating condition of hybrid electric tram on the reduced-scale test platform. The proposed method is also compared with state machine control and equivalent consumption minimization strategy to further demonstrate that it has advantages in hydrogen consumption, state of charge fluctuation, efficiency, and fuel cell output power dynamics.