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    <title>Transport Research International Documentation (TRID)</title>
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    <copyright>Copyright © 2026. National Academy of Sciences. All rights reserved.</copyright>
    <docs>http://blogs.law.harvard.edu/tech/rss</docs>
    <managingEditor>tris-trb@nas.edu (Bill McLeod)</managingEditor>
    <webMaster>tris-trb@nas.edu (Bill McLeod)</webMaster>
    <image>
      <title>Transport Research International Documentation (TRID)</title>
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      <link>https://trid.trb.org/</link>
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    <item>
      <title>Comparative noise analysis of electric, diesel and CNG urban public transport buses: A case study of Novi Sad</title>
      <link>https://trid.trb.org/View/2627523</link>
      <description><![CDATA[In the process of energy transition, various options for the gradual replacement of diesel buses in urban transport are being considered, with a focus on vehicles with alternative propulsion systems. Technologies such as electric and compressed natural gas are not only evaluated for their ability to reduce emissions of harmful gases but also for their potential to improve service quality, especially in terms of passenger comfort and noise reduction. There is a belief that passengers in buses with alternative propulsion enjoy a significantly quieter ride compared to those with traditional diesel engines. This paper presents research conducted within the public urban transport system in Novi Sad, aimed at comparative analysis of noise levels between three different propulsion technologies (diesel, electric and compressed natural gas - CNG). Additionally, noise levels at different locations in the vehicle were analysed. The findings confirm that the type of propulsion and the spatial distribution of components inside the vehicle significantly affect internal noise levels, with front section noise in battery electric buses being 5–8 dB lower than in CNG and diesel buses, while the rear section shows a noise increase of up to 7 dB compared to the front section.]]></description>
      <pubDate>Tue, 27 Jan 2026 16:16:16 GMT</pubDate>
      <guid>https://trid.trb.org/View/2627523</guid>
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    <item>
      <title>Narratives of transport transitions: The shift from diesel and petrol to Compressed Natural Gas in Delhi (1980–2012)</title>
      <link>https://trid.trb.org/View/2625346</link>
      <description><![CDATA[This paper examines the transition from diesel and petrol to Compressed Natural Gas in Delhi’s urban transport system between 1980 and 2012 through the Multi-Level Perspective framework on socio-technical transitions. The author argues that Compressed Natural Gas transition was not driven by technological innovation alone, but by a convergence of judicial intervention, actor coalitions, and strategic narrative reframing. The Supreme Court of India played a pivotal role in mandating Compressed Natural Gas adoption, framing access to clean air as a constitutional right. Civil Society Organization, environmental Non-Governmental Organization (NGOs), health experts, and sections of the media constructed a counter-narrative that challenged the dominant fossil fuel regime and positioned Compressed Natural Gas as a socially and environmentally necessary innovation. The Delhi Compressed Natural Gas transition case challenges conventional assumptions of Multi-Level Perspective and shows how judiciary-led interventions and actor coalitions in the Global South can drive sustainability transitions. The case also demonstrates that transitions in developing urban contexts are shaped as much by legal and institutional actions as by technological readiness. A key policy lesson from Delhi’s experience is that successful low-carbon mobility transitions in India are not solely dependent on technological advancement or market incentives, but require strong legal backing to overcome regime resistance, ensure compliance, and protect public interest.]]></description>
      <pubDate>Thu, 18 Dec 2025 15:37:24 GMT</pubDate>
      <guid>https://trid.trb.org/View/2625346</guid>
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    <item>
      <title>Sustainable technology transition in bus fleet management: Integrating life cycle sustainability assessment and multi-objective optimization</title>
      <link>https://trid.trb.org/View/2471087</link>
      <description><![CDATA[This study presents a comprehensive alternative fuel bus fleet management model for sustainable technology transitions. Life cycle sustainability assessment and multi-objective optimization approaches are integrated. The optimal allocation of Electric, Compressed Natural Gas (CNG), and Diesel buses (DBs) is calculated by considering the relative relevance of thirteen sustainability indicators and the boundary of the assessment. When only local sustainability impacts are considered, CNG and electric buses (EBs) manufactured in China are found to be dominant alternatives in the optimal fleet composition. However, when the system boundary is enlarged with consideration of all global supply-chain-related impacts, the optimal fleet composition significantly changes, and the model mainly favors CNG buses produced in Sweden. The results highlight two crucial aspects of sustainability assessment: 1) System boundary (consideration of local or global impacts) selection in life cycle sustainability assessment and 2) decision-makers priorities about social, economic, and environmental impacts significantly affect the selection of sustainable alternatives. Thus, management of sustainable technology transition, in the case of this paper, “sustainable bus fleet management,” requires a comprehensive and integrated consideration of three pillars of sustainability, impacts embodied in the global supply chains, and decision-makers priorities with consideration of both local and global indicators.]]></description>
      <pubDate>Fri, 13 Dec 2024 17:02:42 GMT</pubDate>
      <guid>https://trid.trb.org/View/2471087</guid>
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    <item>
      <title>Influence of air spring parameters to tyre wear</title>
      <link>https://trid.trb.org/View/2401910</link>
      <description><![CDATA[When using CNG buses, abnormal tire wear started to occur. To identify possible causes of this phenomenon, verify its impact by practical experiment and suggest solutions. During the experiment, three same vehicles were set up with different air spring settings, resulting in different clear heights of 325 mm, 335 mm, 345 mm. After approx. 45,000 km, tire wear was examined, tire defects were measured and compared. Vehicle most affected by heel-toe wear was one with the highest clear height of 345 mm. Higher clear height negatively influences tire wear, but it is clear that other causes are included in this problem. Experiment and calculations affirmed that the primary cause of the tire wear irregularities is vibrations applied to tires caused by added weight. This theory is confirmed by an investigation more prescribed in the introduction section.]]></description>
      <pubDate>Tue, 30 Jul 2024 14:35:54 GMT</pubDate>
      <guid>https://trid.trb.org/View/2401910</guid>
    </item>
    <item>
      <title>Comparative analysis of the performance, environmental impact, and costs of electric, combustion, and gas buses in an operating context of a mid-sized city of an emerging country</title>
      <link>https://trid.trb.org/View/2382340</link>
      <description><![CDATA[With the growing concern about climate change and the need to reduce greenhouse gas (GHG) emissions, the automotive industry has experienced a significant shift towards cleaner and more sustainable transportation options. This article aims to provide an analysis and comparison between Electric Battery Buses (EBBs), Diesel Buses (DBs), and Compressed Natural Gas Buses (CNGBs) in terms of their performance, environmental impact, and investment and operating costs. The case study uses Eclipse SUMO to simulate routes, traffic, consumption, and emissions. Also, to obtain the necessary data for the analysis, road corridors, speed limits, congestion times and levels, and even driving behavior are entered into the software. This evaluation has two parts. First, technical, environmental, and economic indices let us compare the performance of the three types of buses. Subsequently, a sensitivity analysis is performed to establish the economic viability of EBBs and CNGBs compared to DBs. This case study is carried out for Pasto City, Colombia, which has the characteristics of a mid-sized city with around 1,181 km2, 450,000 inhabitants, and mountainous topography; in addition, Colombia has a lot of renewable energy with around 70 % of hydraulic energy. Moreover, the authors provide valuable information for users, policymakers, and entities in charge of decision-making and management of public transport systems.]]></description>
      <pubDate>Thu, 30 May 2024 11:58:31 GMT</pubDate>
      <guid>https://trid.trb.org/View/2382340</guid>
    </item>
    <item>
      <title>Cost-effectiveness analysis of compressed natural gas implementation in the public bus transit fleet in Delhi, India</title>
      <link>https://trid.trb.org/View/1889133</link>
      <description><![CDATA[Buses in Delhi have been fueled by compressed natural gas (CNG) since 2000, at significant expense, to improve air quality. The authors evaluate the emissions impacts and cost-effectiveness of CNG buses relative to diesel, in the early 2000s, and more recently – given stricter vehicle emission standards – in Delhi, and the Indian context. The authors also analyze the hypothetical use of cleaner diesel buses, instead of CNG, in the early 2000s. The authors consider health critical and greenhouse gas emissions, and capital, operating and maintenance costs, over the service life of buses. A scenario analysis is conducted to assess bus fleet emissions due to the higher costs of CNG buses resulting in some trips being shifted to diesel buses, or other modes. CNG buses in the early 2000s significantly reduced particulate and greenhouse gas emissions, relative to the diesel buses they replaced, and also cleaner diesel buses complying with more stringent BS-III/IV standards. However, these cleaner diesel buses would likely have produced emission reductions as or more cost-effectively as CNG. The emission reductions due to low-floor BS-III/IV compliant CNG buses relative to their diesel counterparts, during 2010–2015, were lower, and were as or less cost effective, compared with CNG buses relative to diesel in the early 2000s. The scenario analysis revealed that, under a budget constraint, it is preferable to remove diesel buses, and allow other motor vehicles to meet any shortfall in CNG bus supply, strictly from a particulate and nitrogen oxide emissions perspective. So, allowing only CNG buses to operate in Delhi was an effective policy choice in the early 2000s for mitigating local air pollution. The authors finally explore the implications of the results for mitigating emissions from bus fleets in Delhi and other Indian cities going forward.]]></description>
      <pubDate>Mon, 20 Dec 2021 09:14:28 GMT</pubDate>
      <guid>https://trid.trb.org/View/1889133</guid>
    </item>
    <item>
      <title>Dynamic simulation and life cycle greenhouse gas impact assessment of CNG, LNG, and diesel-powered transit buses in British Columbia, Canada</title>
      <link>https://trid.trb.org/View/1769518</link>
      <description><![CDATA[In this study, a regional life-cycle assessment (LCA) framework is developed to assess compressed natural gas (CNG) and liquefied natural gas (LNG) as fuel alternatives to diesel for a transit bus in Victoria, British Columbia, Canada. The driving pattern and road gradient of a public transit bus route are considered in both directions to capture real-world driving behavior. The real-time fuel consumption and emissions of the transit bus configurations are calculated by dynamic vehicle simulation using Simcenter Amesim software. By considering the effect of road gradient, a 12% difference in computed fuel consumption is shown for bus travel in the two opposing directions of the bus line. The results also reveal that the majority of life cycle greenhouse gas (GHG) emissions are associated with on-board emissions. Overall, switching from diesel to CNG or LNG reduces GHG emissions by 4.8% and 8.1%, respectively.]]></description>
      <pubDate>Tue, 06 Apr 2021 16:55:07 GMT</pubDate>
      <guid>https://trid.trb.org/View/1769518</guid>
    </item>
    <item>
      <title>Long short-term memory network-based emission models for conventional and new energy buses</title>
      <link>https://trid.trb.org/View/1762056</link>
      <description><![CDATA[Public transportation is regarded as a mitigation measure for addressing climate change and air quality deterioration. However, it is still necessary to estimate the emissions of transit buses, in particular when heavy loads and long periods of operation result in increased emission levels. Consequently, the primary objective of this study is to establish a method to estimate CO, CO₂, HC, NOₓ emissions of buses with four different fuel types including gas-electric hybrid electric buses (GEHE buses), compressed natural gas buses (CNG buses), EURO 4 heavy-duty diesel engine buses (EURO 4 buses) and EURO 5 heavy-duty diesel engine buses (EURO 5 buses) based on the long short-term memory network. The proposed models can fully consider the time dependence of emissions response to vehicle operation situation. In addition, to evaluate the performance of the proposed models, an effective emission model which also addressed the time dependence of emissions by taking the elapsed time of acceleration and deceleration into account, was developed for emissions on each route for comparison. According to the estimation results, the emission models developed in this study performed better than the compared method in terms of emission rates and average emission factors, whose root mean squared errors (RMSE) were explicitly lower than the compared method, mean absolute percentile errors (MAPE) were lower than 50% of the compared method, and the predicted average emission factors were relatively more accurate than those of the compared models.]]></description>
      <pubDate>Fri, 26 Feb 2021 16:56:31 GMT</pubDate>
      <guid>https://trid.trb.org/View/1762056</guid>
    </item>
    <item>
      <title>Using the Birmingham National Fuel Cell Bus Program for Regional Outreach in Ohio</title>
      <link>https://trid.trb.org/View/1708826</link>
      <description><![CDATA[This report is an addendum to the final report to the Federal Transit Administration (FTA) covering the project performance and results for the development, build, and demonstration of a fuel cell electric bus in Birmingham, Alabama. Following that demonstration, the bus was shipped to the Stark Area Regional Transit Authority (SARTA) in Canton, Ohio. SARTA staff were trained on and repaired the bus, which was then used in educational outreach to middle schoolers in Ohio. This project also included a study evaluating the performance of hydrogen fuel cell buses in comparison to conventional fuel technologies.]]></description>
      <pubDate>Wed, 03 Jun 2020 09:08:18 GMT</pubDate>
      <guid>https://trid.trb.org/View/1708826</guid>
    </item>
    <item>
      <title>LNG Bus Emissions Prediction Using Neural Network</title>
      <link>https://trid.trb.org/View/1635122</link>
      <description><![CDATA[Being a key feature in any developed society, transportation systems play a vital role to satisfy mobility and accessibility needs. Urbanization, an expanding transport sector and timely access to any specific location are the pivotal factors that contribute to the negative impact on environment. Vehicular emissions such as carbon monoxide (CO), nitrogen oxides (NOx), hydrocarbons (HC), and carbon dioxide (CO₂) are anthropogenic in nature. This study corroborates the use of a neural network model for the prediction of vehicular emissions based on actual road data of Liquefied natural gas (LNG) buses measured by portable emissions measurement system, running on line no. 51 in Zhenjiang, China. The data encompasses speed, acceleration, road grade, and passenger load as the inputs and indicative emissions (CO₂, NOx, CO, and HC) as outputs. This research aims at LNG transit bus emissions modeling based on vehicular and road parameters to measure vehicle specific power correlation with vehicular emissions.]]></description>
      <pubDate>Fri, 20 Sep 2019 15:14:44 GMT</pubDate>
      <guid>https://trid.trb.org/View/1635122</guid>
    </item>
    <item>
      <title>Quantification of a safety target for an underground CNG bus terminal in Stockholm</title>
      <link>https://trid.trb.org/View/1630016</link>
      <description><![CDATA[There are currently no detailed regulations or guidelines for designing the safety concept for an underground terminal for buses powered by compressed natural gas (CNG). Neither are there any explicit safety targets for this type of facility in legislation or common practice. A dilemma arises both in the land-use planning process and building design process when evaluating whether the safety of such a bus terminal is sufficient. However, there are internationally accepted principles in other sectors that may be useful in defining a safety target in this case. In this paper it is proposed that such a safety target can be quantified using risk acceptance criteria expressed in terms of individual and societal risk. The method developed in this study is based on comparisons with risk acceptance criteria applied in other types of facilities and activities, both nationally and internationally, and required an extensive inventory of these. The method also takes into account the fact that people's perceptions of risks affect their acceptance. The proposed safety target is presented in terms of an upper and a lower F-N curve, and includes the ALARP principle. In addition to this a maximum average risk (PLL) is specified for the facility. A plausibility check was carried out indicating that the risk level defined by the safety target is lower than, or of the same order of magnitude as, many other corresponding risks in society, e.g. in other transport systems.]]></description>
      <pubDate>Wed, 19 Jun 2019 11:05:16 GMT</pubDate>
      <guid>https://trid.trb.org/View/1630016</guid>
    </item>
    <item>
      <title>Optimal Design of Bus Routes for Different Vehicle Types Considering Various Driving Regimes and Environmental Factors</title>
      <link>https://trid.trb.org/View/1592824</link>
      <description><![CDATA[As a major part of public transportation systems, bus transit has been regarded as an effective mode to alleviate traffic congestion and solve vehicle emission problems. The performance of a bus transit system depends largely on the design of bus stop locations. This research proposes a multi-period continuum model (peak and off-peak hours) to optimize the design of a bus route for four different vehicle types (i.e., supercharge bus, compressed natural gas (CNG) bus, lithium-ion battery bus, and diesel bus) considering driving regimes and pollutant cost. Inter-stop driving regimes—acceleration, cruising, coasting, and deceleration—are explicitly introduced into the optimization to determine whether and how the coasting regime should be undertaken in the tradeoff between commercial speed of vehicles and operating costs. The cost effectiveness of each alternative has been investigated in a life cycle and compared with respect to different vehicle types. The method has been applied to the real-world bus route no. 7 in Yaan City (China). The results of numerical experiments show that through optimization the total system cost can be reduced by more than 50%. The results of the continuum model are validated by comparison with the discretized results, and the outcomes are similar (with error less than 3%). Finally the life-cycle cost of the four vehicle types is analyzed, and the results indicate that, because of high purchase prices, it is difficult for clean-energy buses to outperform conventional buses in a life cycle (normally eight years), unless subsidies are provided.]]></description>
      <pubDate>Wed, 01 May 2019 12:18:33 GMT</pubDate>
      <guid>https://trid.trb.org/View/1592824</guid>
    </item>
    <item>
      <title>Assessment of GHG Mitigation and CDM Technology in Urban Transport Sector of Chandigarh, India</title>
      <link>https://trid.trb.org/View/1582330</link>
      <description><![CDATA[The increase in number of vehicles in metropolitan cities has resulted in increase of greenhouse gas (GHG) emissions in urban environment. In this study, emission load of GHGs (CO, ABO, CO2) from Chandigarh road transport sector has been estimated using Vehicular Air Pollution Inventory (VAPI) model, which uses emission factors prevalent in Indian cities. Contribution of 2-wheelers (2-w), 3-wheelers (3-w), cars, buses, and heavy commercial vehicles (HCVs) to CO, ABO, CO2, and total GHG emissions was calculated. Potential for GHG mitigation through clean development mechanism (CDM) in transport sector of Chandigarh under two scenarios, i.e., business as usual (BAU) and best estimate scenario (BES) using VAPI model, has been explored. A major contribution of GHG load (~ 50%) in Chandigarh was from four-wheelers until 2011; however, it shows a declining trend after 2011 until 2020. The estimated GHG emission from motor vehicles in Chandigarh has increased more than two times from 1065 Gg in 2005 to 2486 Gg by 2011 and is expected to increase to 4014 Gg by 2020 under BAU scenario. Under BES scenario, 30% of private transport has been transformed to public transport; GHG load was possibly reduced by 520 Gg. An increase of 173 Gg in GHGs load is projected from additional scenario (ADS) in Chandigarh city if all the diesel buses are transformed to CNG buses by 2020. Current study also offers potential for other cities to plan better GHG reduction strategies in transport sector to reduce their climate change impacts.]]></description>
      <pubDate>Mon, 01 Apr 2019 10:15:33 GMT</pubDate>
      <guid>https://trid.trb.org/View/1582330</guid>
    </item>
    <item>
      <title>PresidiGo Capital Plan: A Technical Analysis of Alternative Transit Fleet Fuels and Transition Strategy</title>
      <link>https://trid.trb.org/View/1591009</link>
      <description><![CDATA[This PresidiGo Capital Plan supports the Presidio Trust’s management decisions regarding purchasing, operating, and maintaining its transit fleet, which currently consists of six heavy-duty compressed natural gas (CNG) transit buses and three medium-duty CNG transit buses. The plan includes an analysis of the opportunities and challenges associated with three different fuel types – CNG, Renewable Natural Gas (RNG), and battery-electric buses (BEB) – and their associated fueling/charging infrastructure needs; the considerations needed to transition from CNG to BEB buses; and potential funding opportunities to support the PresidiGo fleet.]]></description>
      <pubDate>Fri, 22 Mar 2019 10:03:41 GMT</pubDate>
      <guid>https://trid.trb.org/View/1591009</guid>
    </item>
    <item>
      <title>Mixed bus fleet management strategy for minimizing overall and emissions external costs</title>
      <link>https://trid.trb.org/View/1505906</link>
      <description><![CDATA[Diesel buses add substantially to air pollution. To mitigate this problem, more and more clean-energy buses are introduced. Among them, electric bus has been recognized as the cleanest with lower emissions. But the deployment of electric bus is limited by its short travel distance and long charging time. In this paper, based on the approach of remaining life additional benefit-cost (RLABC), we propose an approach called new life additional benefit-cost (NLABC) to solve the mixed bus fleet management (MBFM) problem. An integer program is developed based on the NLABC analysis for maximizing the total net benefit of early replacement, where both the optimal fleet size and composition under budget constraints can be determined. Arguably, the routing problem is a major issue to be tackled due to the range limitations and operating costs of electric buses in the MBFM problem. Hence, the authors include the routing problem associated with bus services coordination among multiple routes in this formulation. Two routing methods are proposed to solve the recharging problem to study the tradeoff between accuracy and efficiency. Four types of buses, including electric bus, compressed natural gas bus, hybrid-diesel bus, and diesel bus, are considered, while accounting for their different operating costs, external costs of emissions, and purchase costs. To illustrate the approach, the authors apply the formulation to some transit lines in Hong Kong. The results show that vehicle routing with bus service coordination and mixed fleet optimization are important considerations for managing the bus fleet; both of which can produce considerable benefits.]]></description>
      <pubDate>Thu, 19 Apr 2018 10:02:58 GMT</pubDate>
      <guid>https://trid.trb.org/View/1505906</guid>
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