Analyses of technical options for mitigating CO2 emissions from an urban transport system: a case study of Beijing City

This paper aims to extrapolate the energy consumption and environmental emissions data on the urban passenger transport system in Beijing, to assess the cost-effectiveness and emission reduction potential of promising technology options for transport systems, and to identify options with both reduction potential and cost-effectiveness. Furthermore, it identifies major barriers to the adoption of such options in Beijing. The long-range Energy Alternatives Planning model, the least-cost approach and the Analytical Hierarchy model are used for these three purposes, respectively. The results show that the fuel demand in the Beijing urban passenger transport system will increase rapidly in the future, along with travel demand and vehicle stock. For CO₂ mitigation targets, diesel vehicles have both emission reduction potential and cost-effectiveness, followed by mass rapid transport systems. The ranking of barriers is similar for all three technology options, and found to be financial incentive, public awareness, lack of infrastructure, high initial cost and institutional/administrative barriers, in descending order of importance. Lack of financial incentive plays a very important role in the adoption of new technology options.     

Evaluation of carbon emission reductions promoted by private driving restrictions based on automatic fare collection data in Beijing,China

Public transportation automatic fare collection (AFC) systems are able to continuously record large amounts of passenger travel information, providing massive, low-cost data for research on regulations pertaining to public transport. These data can be used not only to analyze characteristics of passengers’ trips but also to evaluate transport policies that promote a travel mode shift and emission reduction. In this study, models combining card, survey, and geographic information systems (GIS) data are established with a research focus on the private driving restriction policies being implemented in an ever-increasing number of cities. The study aims to evaluate the impact of these policies on the travel mode shift, as well as relevant carbon emission reductions. The private driving restriction policy implemented in Beijing is taken as an example. The impact of the restriction policy on the travel mode shift from cars to subways is analyzed through a model based on metro AFC data. The routing paths of these passengers are also analyzed based on the GIS method and on survey data, while associated carbon emission reductions are estimated. The analysis method used in this study can provide reference for the application of big data in evaluating transport policies.

Implications: Motor vehicles have become the most prevalent source of emissions and subsequently air pollution within Chinese cities. The evaluation of the effects of driving restriction policies on the travel mode shift and vehicle emissions will be useful for other cities in the future. Transport big data, playing an important support role in estimating the travel mode shift and emission reduction considered, can help related departments to estimate the effects of traffic jam alleviation and environment improvement before the implementation of these restriction policies and provide a reference for relevant decisions.     

Issues in evaluating the long-term global impacts of transport policy

This paper provides an overview of issues involved in evaluating the long-term impacts of transport policy. It considers the effects of global warming, and the costs and benefits of action to reduce emissions of greenhouse gases. The overall case for such action rests on the choice of discount rate. The paper considers the relative effectiveness of taxes and regulations in controlling emissions from the transport sector, and contrasts direct action on road traffic with indirect action via policies to increase travel on public transport. After a brief mention of the issue of biodiversity, the paper concludes with some reflections on the political acceptability of different policies.     

Sensitivity of carbon sequestration costs to soil carbon rates

Modifying current agricultural management practices as a means of sequestering carbon has been shown to be a relatively low cost way to offset greenhouse gas emissions. In this paper we examine the sensitivity of the estimates of the amount of soil carbon sequestered and the implied costs of sequestering a tonne of carbon to changes in the rates of soil carbon sequestered for alternative production practices. An application is made to the dryland grain production systems of the US Northern Plains where the marginal costs of soil C range from $20 to $100 per MT. We show that the resulting changes in the marginal costs quantities of C sequestered are not a monotonic transformation of the changes in the soil carbon rates. These results underscore the importance of using a linked economic and biophysical simulation model to assess the economic potential for sequestering carbon in agricultural soils.     

Stochastic-convective transport with nonlinear reactions and mixing: finite streamtube ensemble formulation for multicomponent reaction systems with intra-streamtube dispersion

An effective streamtube ensemble method is developed to upscale convective-dispersive transport with multicomponent nonlinear reactions in steady nonuniform flow. The transport is cast in terms of a finite ensemble of independent discrete streamtubes that approximate convective transport along macroscopically averaged pathlines and dispersive transport longitudinally as microscopic mixing within streamtubes. The representation of fate and transport via a finite ensemble of effective linear streamtubes, allows the treatment of arbitrarily complex reaction systems involving both homogeneous and heterogeneous reactions, and longitudinal dispersive/diffusive mixing within streamtubes. This allows the use of reactive-transport codes designed to solve such problems in an Eulerian framework, as opposed to reliance on closed-form (convolutional or canonical) expressions for reactive transport in exclusively convective streamtubes. The approach requires both reactive-transport solutions for a representative ensemble of one-dimensional convective-dispersive-reactive streamtubes and the distribution of flux over the streamtube ensemble variants, and it does not allow for lateral mixing between streamtubes. Here, the only ensemble variant is travel time. The discussion details the way that the conventional Eulerian fate and transport model is converted first into an ensemble of transports along three-dimensional streamtubes of unknown geometry, and then to approximate one-dimensional streamtubes that are designed to honor the important global properties of the transport. Conditions under which such an 'equivalent' ensemble of one-dimensional streamtubes are described. The breakthrough curve of a nonreactive tracer in the ensemble is expressed as a combined Volterra-Fredholm integral equation, which serves as the basis for estimation of the distribution of flux over the variant of the ensemble, travel time. Transient convective speed and the effects of errors in flux distributions are described, and the method is applied to a demonstration problem involving nonlinear multicomponent reaction kinetics and strongly nonuniform flow.     

Energy efficiency of engines and appliances for transport on land,water, and in air

The transport sector is fundamental for the economy but also for personal life. With a growing population and the globalization process, it is not surprising that the demand of transport is set to grow in the near future and certainly until 2050. This paper focuses on the huge potential of progress in the sector of technology for transport. As the principal sector for transport will remain on roads, the paper emphasizes the progress in the automotive sector. Since car manufacturers are investing massively into research and technology development to offer ever more efficient cars—not only energy efficient but also efficient in terms of safety and comfort—the car of tomorrow will be very different from the present one. The increasing role of electronics in cars will synergistically cooperate with that of so-called smart cities. The potential development of methane in the transport sector, mainly used for heavy transportation is discussed.     

Passenger transport and CO2 emissions: What does the French transport survey tell us?

The aim of this article is to analyse CO₂ emissions caused by passenger transport in France: which socio-demographic groups travel, for what kinds of journey (local or long distance), how and why? Research focusing on the analysis of individual travel can improve the understanding of CO₂ emissions by identifying upstream socio-economic factors, and also enable a better assessment of the potential social impact of measures introduced to limit greenhouse gases due to transport.Calculations are based on the latest French national transport survey (1994). Distances covered and CO₂ emissions were estimated for each journey and for each surveyed individual. A socio-demographic characteristic typology was built and results were obtained through this analysis.If equity and accessibility issues are to be taken into account, planned policies cannot be of the same type if linked to mobility segments. An environmental tax system to limit CO₂ emission increases appears appropriate for long-distance trips. Results are more varied for local journeys, which are often more of a necessity. Nevertheless, income brackets, and measures concerning urban planning or the growth of new car fleets, seem more pertinent.     

A comparative analysis of using trip-based versus link-based traffic data for regional mobile source emissions estimation

The current method used for calculating vehicle emissions integrates travel data and associated vehicle emission factors. Travel data from traditional travel demand models are normally link-based (e.g., volumes on roadway segments), while California emission factors are trip-based (i.e., average emission factors over an entire trip), creating a mismatch in the modeling interface. Using dynamic simulation for trip assignment, we present a new modeling framework that consistently provides both trip-based and link-based VMT-speed distributions. Using the Sacramento Metropolitan Area and Kern County in California, we demonstrate the feasibility of this new method and quantify the effects of using trip-based versus link-based travel data on regional peak period emission inventories. The comparison results indicate that for the base scenario in both studied regions, the link-based method generally results in higher emissions than the trip-based method. The sensitivities of the link and trip-based methods to road network variations also appear dissimilar. The link-based emissions are more sensitive to facility-related changes, while the trip-based emissions are more sensitive to demand-related changes. This suggests that greater care may need to be taken to specify the effects of this modeling interface issue within the transportation conformity process and subsequent mobile emissions analysis.     

Evaluation of energy intensity of transport service sectors in Vietnam

This research analyses energy intensity of transport service sectors in Vietnam and its changing trend in the past years using IO tables and LMDI decomposition method. Energy consumption of 38 economic sectors in 2007, 2012 and 2018 is determined, of which transport service sectors were the second largest energy consumer (17.71 Mtoe), occupied 18.5% of total energy consumed in Vietnamese economy in 2018. In terms of energy intensity, a rising trend is seen in all transport service sectors, of which four most important transport services including bus and other road passenger transport, freight transport service by road and pipeline, waterway shipping freight and aviation passenger reached 0.62 kgoe/USD, 0.72 kgoe/USD, 0.60 kgoe/USD and 0.62 kgoe/USD in 2018, respectively. The ineffective structural change and ineffective energy intensity change are the reasons behind the upward trend in these sectors. Using Leontief inverse, the study also unveils how demanded on transport services by other economic sectors in terms of energy and how much energy embodied in all inputs of any economic sector. In order to keep the energy intensity stable and gradually decreasing, the recommendations are focused on effectiveness in structural changes and improvements in energy efficiency.

     

Description of hydrogeologic heterogeneity and evaluation of radionuclide transport at an underground nuclear test

Realistic models of contaminant transport in groundwater demand detailed characterization of the spatial distribution of subsurface hydraulic properties, while at the same time programmatic constraints may limit collection of pertinent hydraulic data. Fortunately, alternate forms of data can be used to improve characterization of spatial variability. We utilize a methodology that augments sparse hydraulic information (hard data) with more widely available hydrogeologic information to generate equiprobable maps of hydrogeologic properties that incorporate patterns of connected permeable zones. Geophysical and lithologic logs are used to identify hydrogeologic categories and to condition stochastic simulations using Sequential Indicator Simulation (SIS). The resulting maps are populated with hydraulic conductivity values using field data and Sequential Gaussian Simulation (SGS). Maps of subsurface hydrogeologic heterogeneity are generated for the purpose of examining groundwater flow and transport processes at the Faultless underground nuclear test, Central Nevada Test Area (CNTA), through large-scale, three-dimensional numerical modeling. The maps provide the basis for simulation of groundwater flow, while transport of radionuclides from the nuclear cavity is modeled using particle tracking methods. Sensitivity analyses focus on model parameters that are most likely to reduce the long travel times observed in the base case. The methods employed in this study have improved our understanding of the spatial distribution of preferential flowpaths at this site and provided the critical foundation on which to build models of groundwater flow and transport. The results emphasize that the impacts of uncertainty in hydraulic and chemical parameters are dependent on the radioactive decay of specific species, with rapid decay magnifying the effects of parameters that change travel time.     

An assessment of the impact of climate change on air quality at two UK sites

Possible effects of climate change on air quality are studied for two urban sites in the UK, London and Glasgow. Hourly meteorological data were obtained from climate simulations for two periods representing the current climate and a plausible late 21st century climate. Of the meteorological quantities relevant to air quality, significant changes were found in temperature, specific humidity, wind speed, wind direction, cloud cover, solar radiation, surface sensible heat flux and precipitation. Using these data, dispersion estimates were made for a variety of single sources and some significant changes in environmental impact were found in the future climate. In addition, estimates for future background concentrations of NO_x, NO₂, ozone and PM₁₀ upwind of London and Glasgow were made using the meteorological data in a statistical model. These showed falls in NO_x and increases in ozone for London, while a fall in NO₂ was the largest percentage change for Glasgow. Other changes were small. With these background estimates, annual-average concentrations of NO_x, NO₂, ozone and PM₁₀ were estimated within the two urban areas. For London, results averaged over a number of sites showed a fall in NO_x and a rise in ozone, but only small changes in NO₂ and PM₁₀. For Glasgow, the changes in all four chemical species were small. Large-scale background ozone values from a global chemical transport model are also presented. These show a decrease in background ozone due to climate change. To assess the net impact of both large scale and local processes will require models which treat all relevant scales.     

A bottom-up clustering approach to identify bus driving patterns and to develop bus driving cycles for Hong Kong

Bus transport has been an important mode taking up a significant share of urban travel demand and thus the corresponding impacts on the environment are of great concerns. Use of driving cycles to evaluate the environmental impacts of buses has attracted much attention in recent years worldwide. The franchised bus service is currently playing important roles in the public transport system in Hong Kong; however, there is no driving cycle developed specifically for them. A set of bus driving cycle was therefore developed using a bottom-up approach where driving data on the bus network with mixed characteristics were collected. Using the Ward’s method for clustering, the collected data were then categorized into three clusters representing distinct franchised bus route patterns in Hong Kong. Driving cycles were then developed for each route pattern including (i) congested urban routes with closely spaced bus stops and traffic junctions; (ii) inter-district routes containing a number of stop-and-go activities and a significant portion of smoother high speed driving; and (iii) early morning express routes and mid-night routes connecting remote residential areas and urban areas. These cycles highlighted the unique low-speed and aggressive driving characteristics of bus transport in Hong Kong with frequent stop-and-go activities. The findings from this study would definitely be helpful in assessing the exhaust emissions, fuel consumptions as well as energy consumptions of bus transport. The bottom-up clustering approach adopted in this study would also be useful in identifying specific driving patterns based on vehicle speed trip data with mixed driving characteristics. It is believed that this approach is especially suitable for assessing fixed route public transport modes with mixed driving characteristics.

     

A Microcomputer-based Forecasting Model: Potential Applications for Emergency Response Plans and Air Quality Studies

Most atmospheric transport and diffusion models within emergency response systems have very limited physics and are forced to rely on the assumption that wind and turbulence conditions at the time of the release will be representative over the period for which dispersion must be predicted. For releases where the principal concern is about the first few kilometers of travel, such an assumption is appropriate. However, for large accidental releases during stable conditions, the plume may travel for several hours before it is diluted to safe levels and the assumption of persistence may be inappropriate, particularly for transport in complex terrain. Under these circumstances, a model that can forecast changes in wind and turbulence conditions is required. We have installed such a model on microcomputers and tested it in complex terrain near Salt Lake City. One-hour tracer releases produced surface concentrations that remain high for much longer times than that expected based on one hour’ travel time with the mean wind at the source height. Furthermore, relatively large concentrations were found at distances of over 40 km from the source. The model was generally able to reproduce the principal features described by the measurements, although some effects of subgrid scale terrain were missed.     

Levels of particulate air pollution,its elemental composition,determinants and health effects in metro systems

The aim of this study was to review and summarise the levels of particulate air pollution, its elemental composition, its determinants, and its potential health effects in metro systems. A number of studies have been conducted to assess the levels of particulate matter and its chemical composition in metro systems. The monitoring equipment used varied and may have led to different reporting and makes it more difficult to compare results between metro systems. Some of the highest average levels of particulate matter were measured in the London metro system. Whereas some studies have reported higher levels of particulate matter in the metro system (e.g. London, Helsinki, Stockholm) compared to other modes of transport (London) and street canyons (Stockholm and Helsinki), other studies reported lower levels in the metro system (e.g. Hong Kong, Guangzhou, and Mexico City). The differences may be due to different material of the wheel, ventilation levels and breaking systems but there is no good evidence to what extent the differences may be explained by this, except perhaps for some elements (e.g. Fe, Mn). The dust in the metro system was shown to be more toxic than ambient airborne particulates, and its toxicity was compared with welding dust. The higher toxicity may be due to the higher iron content. Although the current levels of particulate matter and toxic matter are unlikely to lead to any significant excess health effects in commuters, they should be reduced where possible. It will be difficult to introduce measures to reduce the levels in older metro systems, e.g. by introducing air conditioning in London, but certainly they should be part of any new designs of metro systems.     

Transport impacts on atmosphere and climate: Land transport

Emissions from land transport, and from road transport in particular, have significant impacts on the atmosphere and on climate change. This assessment gives an overview of past, present and future emissions from land transport, of their impacts on the atmospheric composition and air quality, on human health and climate change and on options for mitigation.In the past vehicle exhaust emission control has successfully reduced emissions of nitrogen oxides, carbon monoxide, volatile organic compounds and particulate matter. This contributed to improved air quality and reduced health impacts in industrialised countries. In developing countries however, pollutant emissions have been growing strongly, adversely affecting many populations. In addition, ozone and particulate matter change the radiative balance and hence contribute to global warming on shorter time scales. Latest knowledge on the magnitude of land transport's impact on global warming is reviewed here.In the future, road transport's emissions of these pollutants are expected to stagnate and then decrease globally. This will then help to improve the air quality notably in developing countries. On the contrary, emissions of carbon dioxide and of halocarbons from mobile air conditioners have been globally increasing and are further expected to grow. Consequently, road transport's impact on climate is gaining in importance. The expected efficiency improvements of vehicles and the introduction of biofuels will not be sufficient to offset the expected strong growth in both, passenger and freight transportation. Technical measures could offer a significant reduction potential, but strong interventions would be needed as markets do not initiate the necessary changes. Further reductions would need a resolute expansion of low-carbon fuels, a tripling of vehicle fuel efficiency and a stagnation in absolute transport volumes. Land transport will remain a key sector in climate change mitigation during the next decades.     

Exposure of Drivers to Carbon Monoxide

Eleven new cars were driven around a 35 km route comprising heavily trafficked roads in and around London, and the concentrations of carbon monoxide inside and immediately outside the vehicles were continuously monitored. Average levels of CO between 12 and 60 parts per million were found inside the cars, and these levels were between 30 and 80% of the external concentrations. The internal levels varied according to external changes but the changes were greatly damped by the buffering effect of the ventilation system. Differences in internal CO levels were more marked between vehicles than for different runs in the same vehicle and were probably due to differences in the ventilation systems.

Blood carboxy-hemoglobin concentrations which would arise from the CO exposures were calculated. Published data suggest that carboxy-hemoglobin concentrations within the range found (1.5-3.0%) would not be expected to produce an adverse effect on health; there are conflicting views as to whether driving performance would be impaired.     

Environmental and resource constraints on Asian urban travel

In industrialising countries, personal income has been the main constraint on widespread car ownership. However, incomes are rising rapidly in many Asian cities, so that traffic congestion and air pollution are replacing income as barriers to higher car ownership. Global oil depletion and climate change are potential additional constraints. The main finding of this paper is that private car travel is unlikely to ever be the dominant mode in Asia's large cities. Instead, a combination of public transport and non-motorised travel seems the only feasible means of sustainably meeting the growing transport needs of congested Asian cities.     

A Program Analysis

A comprehensive analysis of inspection maintenance programs is proposed. Effectiveness, costs to the state and to the individual, distribution of cost and benefits, and political and administrative feasibility are examined. Effectiveness is probably the most difficult aspect to project because of changes in design and consequences of maintenance repair on performance. However, using sensitivity analysis, substantial reductions in hydrocarbons and carbon monoxide are foreseen, along with a slight increase in NO_x emissions.

The cost to the state to administer the program is estimated to be between $2.00 and $2.50 per vehicle, which could be covered by the inspection fee. The other direct costs for the driver, lost time, travel, and repairs, may be offset by fuel and tuneup savings which could amount to as much as 50% of the repair bill. Analysis of distribution costs and indirect social consequences cannot be completed until additional information about the effect of income on maintenance is generated. Politically the program is feasible but depends on public support which in turn is sensitive to direct repair costs. Administratively the program suffers greatly if private repair facilities do not have enough adequately trained mechanics.

It is concluded that the benefits of an inspection program do not convincingly outweigh the high costs, possible adverse social impacts, and public opposition and that other alternatives should be examined.     

Modeling Pareto efficient PM10 control policies in Northern Italy to reduce health effects

High PM10 concentrations can cause human health problems, both related to short-term and long-term exposure to particles. In this work the impact of efficient PM10 control problems in Northern Italy is assessed by means of a two-stage methodology. In the first stage a multi-objective optimization approach is applied. The multi-objective problem defines two control objectives (the emission reduction costs and the air quality index) to be minimized varying the decision variables (precursor emission reductions). The solution of the multi-objective problem is the Pareto efficient PM10 control policies. In the second stage, the ExternE methodology is applied to estimate health impacts and external costs for the efficient emission reduction scenarios computed in the first stage. The methodology has been applied over Lombardia region, one of the most polluted areas in Europe.     

Comparison of life-cycle energy and emissions footprints of passenger transportation in metropolitan regions

A comparative life-cycle energy and emissions (greenhouse gas, CO, NO_X, SO₂, PM₁₀, and VOCs) inventory is created for three U.S. metropolitan regions (San Francisco, Chicago, and New York City). The inventory captures both vehicle operation (direct fuel or electricity consumption) and non-operation components (e.g., vehicle manufacturing, roadway maintenance, infrastructure operation, and material production among others). While urban transportation inventories have been continually improved, little information exists identifying the particular characteristics of metropolitan passenger transportation and why one region may differ from the next. Using travel surveys and recently developed transportation life-cycle inventories, metropolitan inventories are constructed and compared. Automobiles dominate total regional performance accounting for 86–96% of energy consumption and emissions. Comparing system-wide averages, New York City shows the lowest end-use energy and greenhouse gas footprint compared to San Francisco and Chicago and is influenced by the larger share of transit ridership. While automobile fuel combustion is a large component of emissions, diesel rail, electric rail, and ferry service can also have strong contributions. Additionally, the inclusion of life-cycle processes necessary for any transportation mode results in significant increases (as large as 20 times that of vehicle operation) for the region. In particular, emissions of CO₂ from cement production used in concrete throughout infrastructure, SO₂ from electricity generation in non-operational components (vehicle manufacturing, electricity for infrastructure materials, and fuel refining), PM₁₀ in fugitive dust releases in roadway construction, and VOCs from asphalt result in significant additional inventory. Private and public transportation are disaggregated as well as off-peak and peak travel times. Furthermore, emissions are joined with healthcare and greenhouse gas monetized externalities to evaluate the societal costs of passenger transportation in each region. Results are validated against existing studies. The dominating contribution of automobile end-use energy consumption and emissions is discussed and strategies for improving regional performance given private travel's disproportionate share are identified.