Conventional Bus Research Articles

Environmental Benefits of Hydrogen-Powered Buses: A Case Study of Coke Oven Gas

This study conducted a Life Cycle Assessment (LCA) of alternative (electric and hydrogen) and conventional diesel buses in a large metropolitan area. The primary focus was on hydrogen derived from coke oven gas, a byproduct of the coking process, which is a crucial step in the steel production value chain. The functional unit was 1,000,000 km traveled over 15 years. LCA analysis using SimaPro v9.3 revealed significant environmental differences between the bus types. Hydrogen buses outperformed electric buses in all 11 environmental impact categories and in 5 of 11 categories compared to conventional diesel buses. The most substantial improvements for hydrogen buses were observed in ozone depletion (8.6% of diesel buses) and global warming (29.9% of diesel buses). As a bridge to a future dominated by green hydrogen, employing grey hydrogen from coke oven gas in buses provides a practical way to decrease environmental harm in regions abundant with this resource. This interim solution can significantly contribute to climate policy goals.

Planning for Introducing Electric Buses Based on Ecological and Financial Impacts

The transition from fossil fuel-powered buses to electric buses has emerged as a central concern in recent years. Governments worldwide are urging this shift in major urban centers as a strategic response to ecological challenges, particularly issues related to pollution and carbon emissions. The primary impediment to the electrification transition lies in real-world financial constraints. Consequently, comprehending both the ecological benefits and financial intricacies of transitioning bus fleets is paramount.In the initial section of this paper, we formulate a mathematical model to assess the reduction in carbon emissions and pollution resulting from a complete transition of the bus fleet. This model is then applied to the city of Sendai, Japan. By comparing the carbon dioxide and emission gases released by conventional buses with those emitted by electric buses, we can discern the impact of employing electric buses on the urban ecological environment.Moving on to the second section, we present a mathematical model delineating the financial aspects of the transition. We use Sendai as a real-world exemplar for our model. The economic model is categorized into expenditures and revenues. Expenditures encompass the acquisition of electric buses, maintenance costs, and carbon taxes. On the income side, we consider bus fares, revenue from bus advertising, the budget of the bus company, and government subsidies. By subtracting expenditures from revenues, we can ascertain the financial ramifications of transitioning to electric buses.Following the evaluation from both ecological and financial perspectives of the bus fleet's electric transition, a third model is constructed mathematically to address the optimal planning solution for a city aiming to fully electrify its bus fleet within a decade. The objective is to achieve cost-efficiency: to be the most economical while meeting ecological goals. Finally, the cities of Sendai, Kunshan, and Nashville serve as subjects for our model, each providing a tailored solution to the transition planning.

Optimizing the photovoltaic-assisted electric bus network with rooftop energy supply

As a clean and renewable resource, solar energy has demonstrated its potential to alleviate the energy vulnerability and grid strain for electric bus systems. In this study, we investigate the optimal design of an electric bus network in which rooftop solar panels are equipped to provide en-route photovoltaic assistance. A continuous-based model is proposed to optimize critical network design variables, including time-varying headway, stop spacing, and deployment of depot chargers. Introducing rooftop solar photovoltaics can significantly reduce range anxiety for electric buses. Compared with conventional electric bus systems, 4.2%–7.8 % daily in-operation time can be extended, while at most 5.7 % fleet size can also be saved per day. The proposed system demonstrates much more advantages in regions where hourly solar irradiance exceeds 1000 W/m2. Sensitivity tests indicate that (1) with a 10 % improvement in energy conversion efficiency, 1.2 % daily fleet size and 7.5 % depot chargers can be reduced; (2) every 50-kWh increase in bus battery capacity would bring a 1.8 % increment in system cost. Increasing the installation area of solar panels can help reduce battery capacity and lower the system cost. A real-world-based case in Panjin City, China is further designed to validate the application of the proposed system.

Differential Pricing Strategies for Airport Shuttles: A Study of Shanghai Based on Customized Bus Ticketing Data

Airport shuttle buses, as a specialized form of bus service, serve as an economical, efficient, and sustainable transportation option for air travelers. In contrast to conventional bus services, airport shuttle bus operations exhibit more pronounced market-oriented characteristics, striving to balance extensive public transport coverage with the optimization of corporate profitability. Although these services outperform regular bus transit in terms of efficiency, they incur higher operational costs. However, existing studies on enhancing profitability and optimizing resource allocation for airport shuttle buses are inadequate. This study proposes a differential pricing strategy based on historical ticketing data. Initially, we analyze the characteristics of orders, users, and reservations within the context of customized bus operations. Leveraging the differences among various groups, we employ clustering techniques to classify seat grades and segment users. Based on the clustering outcomes, we determine distinct price elasticity values for each segment. As the strategies are developed based on seat grades, booking time, and user travel patterns, the numerical experiments indicate that the proposed differentiated pricing strategy can increase the revenue of customized public transport services by at least 41%. This strategy not only enhances the efficiency of resource allocation and service accessibility but also makes the service more financially sustainable.

Alleviating bus bunching via modular vehicles

The notorious phenomenon of bus bunching prevailing in uncontrolled bus systems produces irregular headways and downgrades the level of service by increasing passengers’ expected waiting time. Modular autonomous vehicles (MAVs), due to their ability to split and merge en route, have the potential to help both late and early buses recover from schedule deviation while providing continuous service. In this paper, we propose a novel bus bunching alleviation strategy for MAV-aided transit systems. We first consider a soft vehicle capacity constraint and establish a continuum approximation (CA) model (Model I) to capture the system dynamics intertwined with the MAV splitting and merging operations, and then establish an infinite-horizon stochastic optimization model to determine the optimal splitting and merging strategy. To capture the reality that passengers may fail to board an overcrowded bus, we propose a second model (Model II) by extending Model I to accommodate a hard vehicle capacity constraint. Based on the characteristics of the problem, we develop a customized deep Q-network (DQN) algorithm with multiple relay buffers and a penalized ruin state applicable for both models to optimize the strategy for each MAV. Numerical results show that the strategy obtained via the DQN algorithm is an effective bunch-proof strategy and has a better performance than the myopic strategy for MAV-aided systems and the two-way-looking strategy for conventional bus systems. Sensitivity analyses are also conducted to examine the effectiveness and benefits of the proposed strategy across different operation scenarios.

A seamless bus network without external transfers using autonomous modular vehicles

Recently, autonomous modular vehicles (AMVs) capable of enabling in-motion transfer (IMT), i.e. passengers moving between vehicles while the vehicles are traveling, have been developed. IMT allows new paradigms for public transport operations that can enhance the speed, flexibility, and reliability of the system. We leverage IMT technology to propose the first network-wide seamless, stop-less bus service concept. We recently introduced the concept of a Stop-Less Autonomous Modular (SLAM) bus service, which eliminates the need for passengers to stop at each bus stop while traveling along a bus line. The current work extends this paradigm to the network level by developing a bus service framework in which multiple SLAM bus lines operating on main arterials interact by exchanging pods among each other to provide passengers with a travel experience that not only eliminates most extra passenger stops within a single line, but also eliminates external transfers, i.e. it removes the need to disembark at a bus stop to change buses when transferring from one bus line to another. The result is a high-speed service that provides a completely seamless journey from the passenger’s origin stop to destination stop anywhere in the coverage area, with integrated (i.e. internal) transfers that take place inside the vehicles themselves while they are in-motion. Our results show that while the proposed service has more stringent operating requirements than a comparable conventional bus service, it provides significantly superior performance, reducing passengers’ travel cost by up to 35% under realistic system settings.

Comparisons of Driving Characteristics between Electric and Diesel-Powered Bus Operations along Identical Bus Routes

The energy consumption profiles of conventional fuelled and electric vehicles are different due to the fundamental differences in the driving characteristics of these vehicles, which have been actively researched elsewhere but mostly on the basis of uncommon geographical contexts. This study, therefore, collected driving data on electric and conventional diesel buses running along exactly the same set of bus routes in Hong Kong during normal daily revenue operations. This enabled a fair comparison of driving characteristics for both types of bus under identical real-life, on-road driving conditions, which highlighted the originality and contributions of this study. A three-step approach was adopted to carry out detailed driving pattern analyses, which included key driving parameters, speed–acceleration probability distributions (SAPDs), and vehicle-specific power (VSP) distributions. Results found that route-based comparisons did highlight important differences in driving patterns between electric and diesel buses that might have been smoothed out by analyses with mixed-route datasets. In particular, the spread, intensity, and directions of these differences were found to be exaggerated at the route-based level. The differences in driving patterns varied across different routes, which has significant implications on vehicle energy consumption. Government agencies and/or bus operators should make references to these results in formulating electric bus deployment plans.

Heat and mass transfer analysis of desiccant-coated heat exchanger with desiccants and metal-organic framework for bus air conditioning applications

Desiccant-coated heat exchangers (DCHEs) in air conditioning offer advantages like independent temperature and humidity control, reduced energy consumption, and high performance. However, the availability of desiccants with high water adsorption and low thermal energy requirements is limited. The present study proposes that aluminum fumarate (Al-Fum) MOF-coated heat exchangers will outperform conventional desiccants, especially at low regeneration temperatures (around 50°C). In order to evaluate this hypothesis, the performance of DCHEs was evaluated with a validated analytical model for different solid desiccant coatings: silica gel, zeolite, and Al-Fum MOF. Water vapor sorption characteristics, heat and mass transfer, and adsorption and desorption capacities were determined. The results showed that the Al-Fum MOF-coated heat exchanger outperformed silica gel and zeolite at low regeneration temperatures under adiabatic conditions. The MOF exhibited superior water uptake capacity (0.39 g/g) between 20% and 80% RH compared to the other studied conventional desiccants. Moreover, the MOF achieved the lowest outlet air temperature. At 19.5 g/kgda, the MOF demonstrated higher adsorption rates (4 % and 0.3 %) than zeolite and silica gel. These findings highlight the potential of Al-Fum MOFs as energy-efficient solutions for controlling indoor air humidity, particularly for latent-sensible heat separation systems with conventional vapor compression bus air-conditioning systems.

Enhancing urban mobility: comparative analysis of improvement priorities for conventional and electric buses in Kathmandu city

Enhancing urban mobility: comparative analysis of improvement priorities for conventional and electric buses in Kathmandu city

Techno-economic assessment of renewable hydrogen production for mobility: A case study

Renewable hydrogen produced by water electrolysis from intermittent energy sources (i.e. sun and wind) is considered one of the most promising energy carriers for the decarbonisation of the so-called “hard-to-abate” sectors, especially heavy-duty transport and industry. To this reason, several new projects are currently under development and public fundings are widely available to boost the renewable hydrogen market. In this fast-changing scenario, this paper presents the techno-economic analysis of an integrated system where renewable power generation, electrolytic hydrogen production and final hydrogen use are closely integrated within a specific site, allowing higher efficiency as well as a containment of hydrogen production and handling cost. The analysis here presented considers a specific case study that includes a 12.5 MWP photovoltaic plant, a 5 MW electrolyser capable to produce nearly 300 t/yr. of renewable hydrogen, and a compression and storage system, all located in Sardinia (Italy). Differently from previous studies, this work faces the analysis from two opposite perspectives: on the one hand, it allows the assessment of the levelized cost of hydrogen during the whole project’s life, making the results comparable to those from other similar analyses; on the other hand, it presents the calculation of project’s profitability in terms of net present value, internal rate of return and payback time from the perspective of a potential investor. The analysis shows that a whole investment of about 20.3 M€ is required, which allows to achieve a levelised cost of hydrogen of 4.09 €/kg, which can decrease to 2.97 €/kg considering the revenues from selling oxygen and the overproduction of electricity. The potential use of renewable hydrogen in urban public transport (by means of fuel cell electric vehicles) has been considered as well, in comparison with conventional diesel buses. Despite the lower cost for fuel (0.41 €/km for hydrogen buses vs. 0.72 €/km for diesel buses) and maintenance and repair (0.20 €/km vs. 0.27 €/km), as well as the lower CO2 emission (some 76 t/yr. saved per bus), the very high investment cost for hydrogen-fuelled buses (up to 720,000 €) makes hydrogen still not competitive with diesel for urban transport, being hydrogen buses characterised by a whole specific transport cost of 1.45 €/km, to be compared with 1.04 €/km for diesel buses.

Flexible optimal bus‐schedule bridging for metro operation‐interruption

AbstractUnder the sudden interruption of the metro, it is significant to dispatch emergency bridging buses to evacuate stranded passengers to improve linkage management and service reliability. Aiming at the problem of emergency bridging bus scheduling, considering the remaining capacity of conventional buses, passenger tolerance, and site convenience, a flexible combined emergency bridging bus scheduling model is constructed based on the constraints of vehicle capacity, dispatching capacity, and maximum evacuation times of emergency bridging bus, aiming at minimizing the maximum evacuation time and passenger delay. The improved Harris hawk algorithm is used to solve the model, and the evacuation plan of the demand‐responsive and station‐station bridging lines is obtained. The maximum evacuation time is 41 min, and the average delay of stranded passengers is 19 min. The results show that the maximum evacuation time is 10% and 27% less than the fixed combined and single scheduling. The average delay is 16% and 42% less than the fixed combination and traditional single scheduling. The sensitivity analysis of the influencing factors of emergency bridging bus scheduling is conducted. The results show that the flexible combined emergency bridging bus scheduling model constructed in this paper can improve evacuation efficiency and reduce passenger travel delays.

Simulation-Based Investigation of On-Demand Vehicle Deployment for Night Bus Routes Using the Monte Carlo Method

Public transportation systems, including trams and buses, play a crucial role in urban traffic. However, these traditional modes of transport have some well-known drawbacks, such as long distances between stops, lengthy waiting times, and a lack of privacy. In response to these challenges, an innovative mobility concept called “FLAIT-train” offers potential solutions. The FLAIT-train operates on regular roads and aims to provide DOOR-2-DOOR transport, addressing the issues associated with fixed stops and offering increased accessibility and convenience. In its initial phase, the FLAIT-train operates on exclusive lanes, but it is designed to integrate with other traffic eventually. The vehicle technology of FLAIT-trains closely resembles that of battery electric autonomous vehicles. To assess whether FLAIT-trains can be used as a suitable alternative to conventional public transportation systems, this paper employs traffic simulations that consider key performance indicators, including the average waiting time per passenger, maximum waiting time of a single passenger, average in-vehicle time per passenger, and average occupancy rate of the vehicles. Using SUMO software (“Simulation of Urban Mobility”, version 1.12.0), a night bus service scenario is meticulously designed and generated. Within this scenario, both FLAIT-trains and conventional buses are simulated under identical conditions and based on statistical data.

Analysis of Multi-Modal Public Transit Competing Relationships and Evolutionary Mechanisms in Cities in Cold Regions

In order to reveal the characteristics of the competition and cooperation of multi-modal public transportation in the cities of cold areas and to study the competitive relationship of multi-modal public transportation in cold areas, the urban public transportation system in cold areas is divided into three sub-systems, namely, conventional buses, urban mass transit, and cabs, to analyze the competitive relationship and evolution mechanism of multi-modal public transportation in cities of cold areas. We construct a multi-modal public transit Lotka–Volterra competitiveness model, considering that conventional buses and urban mass transit are mainly dominant in urban public transit systems in cold regions, and introduce the competitive influence effect coefficients and cooperative influence effect coefficients to analyze the mechanism of the evolution of the competitiveness between conventional buses and urban mass transit. The data on traffic supply and demand and travel of the Harbin bus system, a typical city in China, are collected, and the simulation analysis of multi-modal competing relationship and evolution mechanism of conventional bus and urban mass transit competition is carried out, respectively, with Harbin as the research object. The results show that the constructed model can better describe the multi-modal bus competition relationship and evolution mechanism.

A national survey on the effect of the COVID-19 pandemic on school travel in the US. – Parents perspective

The Coronavirus Disease 2019 (COVID-19) pandemic has considerably influenced school transportation in the United States (US), with conventional bus use declining and private vehicle use growing. It has increased traffic congestion, reliance on private autos, and detrimental air quality and sustainability effects. This study investigates the shift in transport mode preferences among parents during school reopening in 2021, focusing on elementary, middle, and high schools. An online questionnaire was distributed to parents in the U.S. The findings indicate a significant shift in parental transportation choices, with reduced reliance on school buses and increased automobile usage. Elementary school parents' bus percentage declined from 39.7% to 36.4% in Spring 2021, while middle and high school parents showed similar trends. School closures led to a shift to online learning platforms which affected academic achievement, with 15.9%, 15.5%, and 17.0% of students performing below average. In Spring 2021, 50.5% of students on the school bus encountered a delay of 0 to 15 min, while 32.4% suffered a wait of 15 to 30 min. In Fall 2021, 51.7% saw a 0 to 15-minute delay, while 31.2% suffered a 15-to-30-minute delay. Understanding the COVID-19 pandemic's effects on school travel patterns will allow policymakers and transportation planners to develop post-pandemic solutions prioritizing safety, justice, and environmental sustainability for similar events in the future.

Research on the improvement of conventional public transportation in the context of population aging

With the aggravation of the trend of population aging, the conventional bus planning and service in Lhasa city need to be adjusted continuously to meet the needs of the elderly, so that they can enjoy convenient transportation services to better integrate into the city life, so the conventional bus improvement in the context of aging is a relevant study. According to the research characteristics of this paper, Lhasa Chengguan District is selected as the research area, and the current situation of regular bus development in the region is briefly analyzed, and based on the Gaode Map API to obtain the station and road network data, the spatial barrier model is used to assess the accessibility of regular buses, and then ArcGIS is used to visualize the data. Finally, the conventional bus improvement strategy adapted to the aging society is proposed from the three aspects of bus stops and road network, bus facilities for aging, and bus service quality, so as to provide the elderly with more convenient, comfortable, and barrier-free bus services, thus realizing the sustainable development of Lhasa City.

Urban Electric Bus Fleet Transition Research Based on Eco-Impact Valuation Model and Discounted Cash Flow Analysis

This paper investigates the transition to an all-electric bus fleet as a strategy for sustainable urban development, focusing on its financial and environmental impacts. Utilizing the Eco-impact Valuation Model, Discounted Cash Flow Analysis (DCF), and the E-bus Replacement Model, the study assesses the feasibility and benefits of replacing conventional diesel buses with electric buses. Firstly, the Eco-impact Valuation Model analyzes and translates the environmental costs of diesel and electric buses into monetary social costs, evaluating the potential cost reduction to society offered by electric buses. Secondly, the DCF is used to demonstrate the potential cost-saving superiority of electric buses over diesel buses within a single investment period, providing a financial perspective on the transition. Lastly, the E-bus Replacement Model plans the phased introduction of electric buses and updates bus routes over the next ten years, based on air quality severity in different city zones. The severity of pollution is ranked using the TOPSIS evaluation model, with influencing factors weighted by the Analytic Hierarchy Process (AHP). The models are applied to three cities, including Houston, Buenos Aires, and Shenzhen, offering insights into the ecological, financial, and practical feasibility of electric buses for policymakers.

A new perspective on the performance comparison of pure electric buses versus converted electric buses in public transportation systems

Abstract The utilization of electric buses presents a viable solution to the reduction of greenhouse gas emissions and the concomitant decrease in fossil fuel consumption. Furthermore, their low-noise operation has the additional benefit of reducing noise pollution, which is a particular issue in large urban areas. This constitutes a significant advantage for public transport systems. Additionally, they provide cost savings in operations and maintenance, which represent a substantial proportion of expenditure for public transport operators. However, the initial purchase cost of electric buses is higher than that of conventional buses (diesel and CNG). This discrepancy can be attributed primarily to the absence of economies of scale in the manufacturing of electric bus subsystems and the substantial expenses associated with non-standardized, disparate technologies, most notably the high-voltage traction battery. The considerable disparity in the upfront cost of electric buses (in comparison to their internal combustion counterparts of equivalent specifications) has prompted a novel strategy among local authorities responsible for the provision of public transportation services: Retrofit! This paper presents, for the first time, a comparison between all-electric buses constructed from the ground up and retrofitted diesel-electric buses in actual public transportation operations. The results obtained will facilitate an evaluation of the retrofit approach within the context of sustainable transport policies, with the ultimate objective of raising awareness among relevant audiences and decision-making mechanisms.

Electrification of public buses in Jakarta, Indonesia: A life cycle study

Indonesia plans to mitigate the environmental emissions, particularly the carbon emissions, from the transport by replacing conventional buses with battery electric buses (BEBs). However, there are limited studies on the potential environmental benefits of BEBs and mostly focused on carbon emissions. In this study, the environmental impacts of adopting BEBs in Jakarta's public transportation system were examined using Life Cycle Assessment (LCA) to better understand its potential environmental impacts. Using LCA, the environmental impacts of BEBs were also compared with conventional buses across their life cycles, which included raw materials extraction until the end of life stages. The results showed diesel buses have generally lower environmental impacts than BEBs due to the high share of fossil fuels in the electricity generation in Indonesia. Scenario analysis showed that extending the life cycle, using different battery disposal methods, and using battery reuse could lead to higher environmental benefits in using BEBs. Among the scenarios considered in the study, prolonging the lifespan of the bus to 32 years, using electricity mix with a higher share of renewable energy and reusing the lithium-ion batteries, BEBs would have lesser environmental impact per kilometre. In particular, the particulate matter formation (PM2.5) dropped 21 %, while the overall life cycle of BEB using the highest renewable scenario showed an average of 25 % improvement compared to the baseline scenario regarding environmental impact.

Pathway of reducing CO2 emission and harmful exhaust gases in transport by using electric buses-the example of Belgrade

The buses have an irreplaceable role in the public transport system, regardless of city size. Buses powered by internal combustion engines (diesel, CNG) are still the most common concept of city buses, but in the last few years, the use of fully electric buses (E-buses) has been growing. One of the reasons for the increasing use of electric buses is their environmental advantages over conventional buses: zero emissions at the local level (Tank-To-Wheel) emission, more favourable carbon dioxide (CO2) emissions at the regional or national level (Well-To-Wheel), and higher energy efficiency. The EKO1 line (Vukov Spomenik-Belvil) has operated in Belgrade since 2016, with five full electric buses. The paper will present the environmental aspects of using electric buses on line EKO1 compared to diesel and CNG buses. The environmental aspects of E-buses were researched through the effects of reducing the emission of harmful exhaust gases caused by eliminating the use of diesel-powered or CNG-powered buses and introducing E-buses. Within the ecological suitability of the using E-buses, the emission of carbon dioxide (CO2) that occurs indirectly during electricity production was researched and a comparison was made with the emissions of CO2 caused by the combustion of diesel fuel and CNG in buses with conventional propulsion. The paper also examined the energy efficiency of buses with different drive systems on the line EKO1, based on the analyzed energy consumption. As a result of the analysis, the introduction of electric buses on the EKO1 line was justified from the point of view of improving the environment through the reduction of harmful gas emissions and decarbonization as well as better energy efficiency.

Comparison of the transportation network for public transit and private vehicles in Shanghai: An accessibility approach

This study examines the differences in service level and coverage of public transit (PT) and private vehicles (PV) with multi-source data in Shanghai. To construct computable networks and address visual results, the constrained shortest path algorithm and a spatial grid accessibility model are employed to seek the optimal path for travelers to city key points. Travel time ratio of PV and PT is applied to reflect the competitiveness of the two modes over different areas of Shanghai. Results show that for PV, although the average travel time meets the needs of car travel, 51 % of the population cannot get to graded city centers within 45 min. In addition, the PV accessibility gradually weakens from the central city to the outside, highways and expressways may be feasible solutions. For PT, half of the population can't reach any city key points within two transfers, and almost all of these people live in the suburbs. Less than 30 % of the population can reach the city key points within 1 h, of which rail transit contributes more than conventional buses. Furthermore, the travel accessibility of PV is much better than that of PT. The average travel time ratio in all comparable grids is 2.04 for hubs, and 2.10 for graded city centers. For travels to graded city centers, the travel time ratio of suburbs is 35 % higher than that of central city, indicating that the inequity distribution of public transportation resources is worse in the suburbs than in the central city. This study also measures equity performance of groups based on spatial location and income level, and we find out that more core locations and higher income lead to higher accessibility. The gap among groups is significant, with a Gini coefficient over 0.5.