TRIBUTE: Trip-based urban transportation emissions model for municipalities

This research aims at developing modeling and scenario-comparison tools to explore the impacts of various transportation and land use planning policies on changing travel behavior and eventually greenhouse gas (GHG) emissions. A Trip-Based Urban Transportation Emissions (TRIBUTE) model is developed. Data required for TRIBUTE comes from household travel surveys and emissions inventories, which is a major advantage in cases where a detailed transportation network model is unavailable. TRIBUTE is composed of two main parts: a mode choice model and an emissions forecasting model. The mode choice model is responsible for estimating modal shares of alternative modes of travel in response to changes in personal, modal, and land use attributes. The emissions forecasting model translates the modal shares into vehicle kilometers traveled, and subsequently GHG emissions. TRIBUTE is a macroscopic model intended to assist municipalities evaluate alternative transportation and land use policy scenarios and eventually select the one(s) that help them meet their future GHG emission targets. This paper reports on the conceptual framework of the developed model and presents a case study.     

Emissions,performance, and design of UK passenger vehicles

Consumer, legal, and technological factors influence the design, performance, and emissions of light-duty vehicles (LDVs). This work examines how design choices made by manufacturers for the UK market result in emissions and performance of vehicles throughout the past decade (2001–2011). LDV fuel consumption, CO₂ emissions, and performance are compared across different combinations of air and fuel delivery system using vehicle performance metrics of power density and time to accelerate from rest to 100 km/h (62 mph, t_z-62). Increased adoption of direct injection and turbocharging technologies helped reduce spark ignition (SI, gasoline vehicles) and compression ignition (CI, diesel vehicles) fuel consumption by 22% and 19%, respectively, over the decade. These improvements were largely achieved by increasing compression ratios in SI vehicles (3.6%), turbocharging CI vehicles, and engine downsizing by 5.7–6.5% across all technologies. Simultaneously, vehicle performance improved, through increased engine power density resulting in greater acceleration. Across the decade, t_z-62 fell 9.4% and engine power density increased 17% for SI vehicles. For CI vehicles, t_z-62 fell 18% while engine power density rose 28%. Greater fuel consumption reductions could have been achieved if vehicle acceleration was maintained at 2001 levels, applying drive train improvements to improved fuel economy and reduced CO₂ emissions. Fuel consumption and CO₂ emissions declined at faster rates once the European emissions standards were introduced with SI CO₂ emissions improving by 3.4 g/km/year for 2001–2007 to 7.8 g/km/year thereafter. Similarly, CI LDVs declined by 2.0 g/km/year for 2001–2007 and 6.1 g/km/year after.     

Research agenda for low-carbon mobility: Issues for New World cities

ABSTRACT

Low-carbon mobility (LCM) features strongly in debates about the sustainability of cities and their resilience in the face of demographic, economic, and climate change. Transport is a major source of carbon emissions and there are indications that these continue to increase, despite the considerable recent advances in vehicle, engine, and fuel technologies. Reducing carbon emissions from transport may become more difficult, not easier. A particular issue relates to the New World cities, typified by those of North America and Australasia, which largely developed from the latter half of the nineteenth century onward and whose transportation systems were largely based around private vehicle ownership and usage. These cities are typically composed of low-density, dispersed suburbs, which are highly car dependent and resource and carbon emission intensive. This article develops a research agenda directed at determining and testing policy and planning measures relevant to the quest for low carbon mobility in New World cities. It suggests a rich agenda for essential research on LCM. Much of this agenda falls within the realm of the integration of transport and land use, with attention to urban design details to enhance the perceptions of and opportunities to use low carbon transport alternatives. Research topics identified for LCM research include (1) urban design and land use–transport integration (LUTI), (2) low carbon mobility policies directed at achieving widespread behavior change, (3) opportunities for new technology and its application, including requirements for systems and infrastructure, and (4) analysis and tools for informed decision making, including modeling, measurement, visualization, and especially assessment.     

城市轨道交通建设采用PPP融资模式的探讨

城市轨道交通建设投资巨大,仅靠政府投资难以满足发展的需要,因此必须采用多种方式筹措建设资金特别是吸引民营资本的进入。通过分析城市轨道交通建设采用PPP模式的总体思路和运作框架,探讨运用PPP模式的3种运作方式,说明该模式是吸引民营资本参与城市轨道交通建设的较好方式,但应建立相应的保障机制。     

Car-sharing organizations: The size of the market segment and revealed change in mobility behavior

Car-sharing organizations (CSO) have recently spread throughout central European cities and currently have 20000 members. They lower individual fixed costs of car availability change the incentive structure of private vehicle use by transforming nearly all costs into variable costs. A survey of all current Austrian CSO members is used to identify the characteristics significant of members. A procedure is proposed to quantify urban local market segment potentials and is applied to two residential areas. The net impact of CSOs depends on how the new incentive structure changes mobility behavior. A controlled experiment of voluntary new members was carried out to compare pre-membership and membership trip structure and modal split. Results indicate a substantial reduction of aggregate private vehicle mileage. While the share of trips by car is constant, changes in trip length are observed, with there being different changes for households which previously owned a car and those which did not. Combining behavior impact with market segment size results in the quantification of emission reduction and car ownership reduction (land use demand) due to car-sharing, which is a decentralized demand-side transport policy.     

Interplay between ethanol and electric vehicles as low carbon mobility options for passengers in the municipality of São Paulo

The Brazilian cities as well as many of the large urban centers in the world continue to expand, increasing the demand for mobility and transport, while, at the same time, the same cities are investing in greenhouse gas (GHG) mitigation to avoid climate change. Brazil's urbanization rate increased from 26% in 1940 to almost 70% in 1980. During this period, the Brazilian population tripled and the urban population multiplied by seven. In 2010, the transport sector in São Paulo accounted for 71% of the total emissions released by the energy sector. Ethanol has been considered a fuel with less greenhouse gas emissions, when compared with fossil fuels. However, ethanol production would have to double to meet the expected demand. Electric vehicles (EVs) market is expanding around the world, and is also an option to reduce the transport emissions, if powered by clean electricity. To assess whether the adoption of EVs might bring more benefits than the current ethanol, we develop prospective scenarios supported by the Long-range Energy Alternatives Planning (LEAP) simulation tool, taking a bottom-up tank-to-wheel approach to consider the CO₂ emissions of car in São Paulo. The scenario considering a substitution of 25% of gasoline-powered cars by EV in 2030 showed a reduction in energy consumption and CO₂ emissions, around 15% and 26% respectively in that year in comparison with 2015. We discuss the interplay between ethanol and EV, also considering emission coefficients from life cycle analysis conducted in Brazil, and concluded EV will have higher positive impact on climate change mitigation than ethanol.     

Optimizing EV-based P&R subsidy policies for commuting corridor based on cross-nested logit model

The promotion of electric vehicles (EVs) is restricted by cruising range limitation and charging station deficiency. Given the mature development of Park and Ride (P&R) mode, which is used in many cities worldwide to attract more travelers to use public transit, a new travel mode, i.e., EV-based P&R is introduced as an alternative for commuters’ daily travel. This seems quite attractive to expand the use of EVs and further increase their market share. This paper aims to investigate the impact of EV-based P&R introduction on travel mode choice along commuting corridor, and further aid in the optimal subsidy policies decision for the government. A bi-level model is proposed to model the presented problem. The lower level describes commuters’ joint mode and transfer choice behavior through a cross-nested logit (CNL) model, while the upper level minimizes the system cost. A genetic algorithm is developed to solve the formulated model with a partial linearization algorithm for solving the lower level model. And a numerical example is then used to demonstrate the effectiveness of the methodology and illustrate how the network flow pattern reshapes due to the introduction of EVs into the P&R mode and the change of corresponding subsidy policies. As the results show, improving the EV hardware, applying the intelligent supporting service system, developing new technologies for EV fast charging, appropriately improving the parking space capacity, and increasing the parking fee of transfer stations near the central business district (CBD) are all helpful to save the social cost and promote the usage of EVs.