Urban bus fleet-to-route assignment for pollutant emissions minimization

This study proposes a methodology to optimize the assignment of an urban bus fleet to a set of fixed routes, taking into account the differences among routes and the differences among vehicle types and propulsion technologies in order to reduce pollutant emissions (CO₂, CO, THC, NO_x and PM). A Mixed Integer Linear Programming optimization model is stated and two scenarios are assessed: minimization of CO₂ and NO_x. The results show that it is feasible to obtain a fleet distribution in which emissions for any given pollutant are reduced without increase in emissions of other pollutants.     

Automobile use,fuel economy and CO2 emissions in industrialized countries: Encouraging trends through 2008?

Car use and fuel economy are factors that determine oil demand and carbon dioxide (CO₂) emissions. Recent data on automobile utilization and fuel economy reveal surprising trends that point to changes in oil demand and CO₂ emissions. New vehicle and on-road fleet fuel economy have risen in Europe and Japan since the mid 1990s, and in the US since 2003. Combined with a plateau in per capita vehicle use in all countries analyzed, these trends indicate that per capita fuel use and resultant tail-pipe CO₂ emissions have stagnated or even declined.Fuel economy technology, while important, is not the only factor that explains changes in tested and on-road fuel economy, vehicle efficiency and transport emissions across countries. Vehicle size and performance choices by car producers and buyers, and driving distances have also played significant roles in total fuel consumption, and explain most of the differences among countries. Technology applied to new vehicles managed to drive down the fuel use per unit of horsepower or weight by 50%, yet most of the potential fuel savings were negated by overall increased power and weight, particularly in the US. Similarly, the promise of savings from dieselization of the fleet has revealed itself as a minor element of the overall improvement in new vehicle or on-road fuel economy. And the fact that diesels are driven so much more than gasoline cars, a difference that has increased since 1990, argues that those savings are minimal. This latter point is a reminder that car use, not just efficiency or fuel choice, is an important determinant of total fuel use and CO₂ emissions.We speculate that if the upward spiral of car weight and power slows or even reverses (as has been observed in Europe and Japan) and the now mandatory standards in many countries have the intended effect that fuel use will remain flat or only grow weakly for some time. If real fuel prices of 2008, which rivaled their peaks of the early 1980s, fell back somewhat but still remain well above their early 2000 values. If the prices remain high, this, combined with the strengthened fuel economy standards, may finally lead to new patterns of car ownership, use and fuel economy. However, if fuel prices continue their own stagnation or even decline after the peaks of 2008 and car use starts upward, fuel use will increase again, albeit more slowly.     

Battery electric vehicles in cities: Measurement of some impacts on traffic and government revenue recovery

We are told that electric vehicles, cars in particular, will be good for the environment. But what exactly might this mean? It is true that end use emissions will be significantly reduced when we move from fossil fuels to green energy sources? Assuming that the demand for such cars, including battery electric vehicles (BEVs) in particular will grow, we can expect a significant number of such vehicles manufactured in future years. Given the potentially relatively lower cost (fewer moving parts) compared to internal combustion engine vehicles as well as the significantly lower usage costs per kilometre, we would expect a level of uptake that could impact on the performance of the road network (perhaps increased congestion and crash risk) but also a concomitant reduced use of public transport and fuel excise loss. In this paper, we apply the MetroScan modelling system in the Greater Sydney Metropolitan Area (GSMA) over the period 2021–2056 to identify the likely impact that the growth in BEV ownership and use will have on vehicle kilometres, modal shares, government revenues, levels of CO₂ emissions and other impacts. Moreover, we investigate the introduction of a BEV usage charge proposed in Australia to see what it might do to these key performance indicators and whether it can offset the adverse effects during BEV uptake such as government fuel excise revenue loss and increased congestion.     

Assessment of transport emissions impact and the associated social cost for Chengdu,China

Chengdu, the capital city of Sichuan province, is the fourth biggest city in China with over 15 million residents and 3.4 million vehicles. In Chengdu, transport and other mobile sources accounted for over 27% of the city's PM_2.5 emissions (CDEPB, 2016), posing negative impacts on public health, local environment, and the climate. This study estimated impacts from transport-related emissions (CO₂, CH₄, N₂O, PM₁₀, PM_2.5, NO_X, SO_X, CO, and HC) and evaluated the associated social cost for Chengdu from 2005 to 2013. The study also assessed the city's transport performance in terms of its eco-efficiency with the socioeconomic and environmental concerns. The activity-based methodology was adopted to produce the emission inventories, while utilizing meta-analysis and localizing the emission social cost factors based on Chengdu's economic and demographic reality to support social cost assessment. The study marks the first attempt in literature to evaluate Chengdu's transport emission social cost. The following were observed in the study: (i) in 2013, the social cost of all transport emissions in Chengdu was around US$3 billion, with the lowest estimate of US$449 million and the highest estimate of US$4.7 billion; (ii) trucks, private cars, and motorcycles were the major contributors, while NO_X, PM_2.5, and CO were the key pollutants to public health; (iii) if GHGs (CO₂, CH₄, and N₂O) were excluded, the upper range of social cost of transport air pollutants would be from US$2.4 billion to US$4.1 billion, or 1.6%–2.8% of the Chengdu's GDP.     

PM,NOx and CO2 emission reductions from speed management policies in Europe

Speed reduction measures rank among the most common schemes to improve traffic safety. Recently many urban streets or entire districts were converted into 30 kph zones and in many European countries the maximum permissible speed of trucks on motorways is under discussion. However, besides contributing to traffic safety, reducing the maximum speed is also seen as beneficial to the environment due to the associated reduced fuel consumption and lower emissions. These claims however are often unsubstantiated.To gain greater insight into the impact of speed management policies on emissions, this paper examines the impact on different traffic types (urban versus highway traffic) with different modelling approaches (microscopic versus macroscopic). Emissions were calculated for specific types of vehicles with the microscopic VeTESS-tool using real-world driving cycles and compared with the results obtained using generalized Copert-like macroscopic methodologies. We analyzed the relative change in pollutants emitted before and after the implementation of a speed reduction measure for passenger cars on local roads (50–30 kph) and trucks on motorways (90–80 kph). Results indicate that emissions of most classic pollutants for the research undertaken do not rise or fall dramatically. For the passenger cars both methods indicate only minor changes to the emissions of NO_x and CO₂. For PM, the macroscopic approach predicts a moderate increase in emissions whereas microscopic results indicate a significant decrease. The effects of specific speed reduction schemes on PM emissions from trucks are ambiguous but lower maximums speed for trucks consistently result in lower emissions of CO₂ and lower fuel consumption. These results illustrate the scientific uncertainties that policy makers face when considering the implementation of speed management policies.     

Using GIS tools to estimate CO2 emissions related to the accessibility of large retail stores in the Oulu region, Finland

Everyday traffic accounts for a significant share of overall greenhouse gas emissions, in particular carbon dioxide (CO₂). While several solutions have been proposed for decreasing the emissions, a new kind of land use planning is required in order to achieve long-term effects. This study focuses on the effect of large retail store locations in the urban structure on overall CO₂ emissions, by using the Oulu region, Finland, as a case study. The aim was to utilize GIS tools to assess store locations in terms of CO₂ emissions from private cars used for consumer traffic. In this case, not only are the locations of the existing and planned retail units investigated with respect to population distribution and car ownership, but the analysis is also carried out by regarding any location within the study area as a hypothetical site for a large retail unit. According to the applied method, CO₂ values are lowest near the centre of the studied region, the region with the highest population density, although the city centre itself did not turn out to be the most optimal location for a retail store in terms of CO₂ emissions. Nevertheless, by generally reducing trip length, a compact urban structure is an important way of achieving long-term cuts in CO₂ emissions.     

Critical aggressive acceleration values and models for fuel consumption when starting and driving a passenger car running on LPG

The models based on vehicle speed have been used to estimate fuel consumption and CO₂ emissions. However, these models could not properly estimate the change in fuel consumption and CO₂ emissions as the speed changes. As for the alternative method, people try to consider using acceleration instead of speed. Although acceleration has been seriously considered, determining critical aggressive acceleration value in relation to fuel consumption and CO₂ emissions is difficult to find. In this study, evaluation models of fuel consumption were developed using instantaneous acceleration, and we defined the critical aggressive acceleration values for different states of the vehicle from the viewpoints of fuel consumption and emissions. We used a mid-sized Liquefied Petroleum Gas (LPG) passenger car and obtained instantaneous data from a digital tachograph installed in the car while it accelerates. We developed two fuel consumption models and found critical aggressive accelerations, respectively: a model of starting vehicle that measures range of speed required to overcome the inertia during acceleration from stop state, and the other model for the driving state. We used Classification and Regression Tree (CART) analysis to find the critical aggressive accelerations at which the increments of fuel consumption change abruptly. As a result, the critical aggressive accelerations causing abrupt change in the increments of fuel consumption were found to be 2.598 m/s² for the starting of vehicles and 1.4705 m/s² when driving them. We also found that the increments of fuel consumption can be explained through quadratic and exponential functions with instantaneous acceleration.     

Factors of electric vehicle adoption: A comparison of conventional and electric car users based on an extended theory of planned behavior

Increasing the share of battery electric vehicles (BEV) in the total car fleet is regarded as a promising way to reduce local car emissions. Based on online surveys in Denmark and Sweden, this study compares BEV users' (n = 673) and conventional vehicle (CV) users' (n = 1794) socio-demographic profiles, attitudinal profiles, and mobility patterns. In line with previous research, BEV users are typically male, highly educated, have high incomes, and often more than one car in their household. Additionally, BEV users perceive less functional barriers toward BEV use and have more positive attitudes and norms than CV users. The different profiles of these user groups suggest a separate analysis of potential factors of BEV adoption in both groups. In regression analyses, CV and BEV users' intention to use/purchase a BEV is modeled based on factors of the Theory of Planned Behavior extended by personal norm, perceived mobility necessities, and BEV experience. For CV users, symbolic attitudes related to BEVs are the most important factor of intention, while perceived functional barriers in terms of driving range are most relevant for BEV users' intention. How BEV users cope with trips of longer distance seems of particular relevance. In multiple car households, we found the percentage of actual BEV usage related to the type of other cars in the household, perceived functional barriers of BEVs as well as (successful) behavioral adaption to longer trips by BEVs. Based on the results, we discuss ways to increase BEV adoption for current users and non-users.     

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.     

Examining individuals preferences for hybrid electric and alternatively fuelled vehicles

This paper examines individuals motivations when purchasing vehicles, focusing upon what factors would encourage individuals to purchase hybrid electrical vehicle (HEV) or alternatively fuelled vehicle (AFV). AFVs in this paper refer to any cars run on alternatives to petrol and diesel. This research attempts to ascertain whether reductions in fuel costs, vehicle registration tax (VRT), or green house gas emissions would encourage individuals to purchase a HEV or an AFV instead of a conventional vehicle. VRT is an Irish tax that is levied on the purchase of new vehicles. One of the motivations to conduct this research was to examine a new car tax and VRT scheme introduced by the Irish government in 2008. This new policy rewards the purchase of environmentally friendly cars, with lower VRT and car tax rates. To understand individuals’ perceptions of these new taxes a survey was sent to recent customers of a car company in Ireland. The survey asked respondents about their recently purchased vehicle and how important they considered vehicle attributes such as environmental performance, fuel cost, and safety, before making their car purchase. The survey also contained a number of stated preference experiments that were designed to ascertain what factors influence individuals’ decisions when purchasing their new car. The results showed that respondents did not rate green house gas emissions or VRT as crucial attributes when purchasing a new vehicle. The vehicle attributes that respondents rated most highly were reliability, automobile safety, fuel costs, and the cost price. The majority of respondents agreed that HEVs and AFVs are better for the environment, cheaper to run than conventional vehicles and would be the vehicle of choice in ten years time.     

Modeling different penetration rates of eco-driving in urban areas: Impacts on traffic flow and emissions

Climate change and air quality are two main environmental challenges in metropolitan areas. As road transportation is one of the main contributors, public administrations are facing these problems with a number of complementary policy measures: shift to cleaner modes, new fuels and vehicle technologies, demand management, and the use of information and communication technologies (ICT) applied to transportation. Eco-driving is one of the measures that present large fuel savings at individual level. Although these savings are well documented in the literature, few studies focus on how eco-drivers driving patterns affect the surrounding vehicles and the traffic in general, and more particularly what would be the impact when the number of eco-drivers grows. Using a traffic microsimulation tool, four models in urban context have been built, corresponding to the different types of urban roads. Both the base-case and the parameters setting to simulate eco-driving have been calibrated with real data collected through floating vehicles performing the trips with normal and eco behaviors. In total, 72 scenarios were simulated, varying the type of road, traffic demand, and the percentage of eco-drivers. Then, the CO₂ and NO_x emissions have been estimated through a microscopic emission model. The results show that in scenarios with low or medium demand levels and increasing number of eco-drivers, the effects are positive in terms of emissions. On the other side, with high percentage of eco-drivers and high traffic demand, the emissions rise. Higher headways and smooth acceleration and decelerations increase congestion, producing higher emissions globally.     

Strategic travel planning toward future emission targets—A comparative analysis of 20 Swedish municipalities applying the CERO model

Organizations displaying best practices for attaining proactive sustainability targets at local level are of major importance as role models in the transition toward a sustainable transport system. This study summarizes results and conclusions from 20 municipalities in Sweden that have implemented the so called CERO analysis in order to adapt to future emission targets for travel. The overall aim of the study is to identify factors explaining why some municipalities are more successful than others in a benchmarking comparison.

The results indicate that commuting by car is by far the most dominant source of emissions, constituting on average 76% of total annual travel emissions (including both commuting and business travel). In order to reduce these emissions, travel planning programs within organizations must address both commuting conditions and business travel conditions to reduce car dependence for work travel, e.g., employees using private cars for business trips most likely also use their own cars for commuting. To identify potential success factors as regards emissions-efficient travel, three comparative statistical analyses were conducted: grouping municipalities with low emissions in relation to the total average; analysis of car commuters' willingness to change travel mode; and before-and-after analyses of municipalities implementing specific action plans. The results revealed that municipalities conducting follow-up studies 2 years after implementing travel planning programs all lowered their total CO₂ emissions, by on average 10% during a 2-year period. Overall, these municipalities achieved redistribution to alternative travel modes but also reduced total travel mileage.     

Measuring the potential implications of introducing a cap and share scheme in Ireland to reduce green house gas emissions

This paper examines some of the potential impacts of introducing a cap and share scheme in Ireland. Under such a scheme a cap or limit is placed on national CO₂ emissions and individuals are allocated an annual CO₂ allowance. The research presented in this paper focuses on travel-to-work trips specifically. CO₂ emissions for these annual work trips are calculated and a cap is determined based on these results. Cap levels are set based on average emissions and a 20% reduction in average emissions as per Ireland's reduction targets. A national and Dublin only cap are examined and the results are presented as a means of comparison. Binary logistic models are used to determine the socio-economic characteristics of individuals who fall above and below the cap. The results demonstrate the importance of car ownership, journey distance, mode choice and household composition in determining whether a commuter is above or below the cap. Many commuters who fall above the cap are likely drive to work over long distances, have dependent children in their household and own more than one car.     

Trends in vehicle kilometres of travel in world cities, 1960–1990: underlying drivers and policy responses

Increases in private motorised urban vehicle kilometres of travel are shown to arise from population growth, urban sprawl, increased car ownership and decreases in vehicle occupancy. In particular, the worldwide increase in urban mobility since 1960 has been the direct result of increased affluence and the consequent greater accessibility of private motor vehicles, as well as population growth. Urban sprawl has significantly less influence, although it has been significant in USA, Canadian and Australian cities. Despite this, a number of cities have shown that clear policy initiatives can contain the growth of urban private motorised mobility.     

The emission reduction potentials of First Generation Electric Aircraft (FGEA) in Finland

Under the looming climate crisis, aviation needs to find new solutions to cut its greenhouse gas emissions. One pathway towards zero emissions is the use of electric aircraft. While current battery technology will not allow for medium and long-haul flights at full capacity, on short-haul routes First Generation Electric Aircraft (FGEA) could play a significant role in the near future. Current FGEA under development could carry 9–19 passengers on distances of 400–1046 km by 2025. This study focuses on the emissions reduction potentials of FGEA in Finland. It compares the carbon dioxide equivalent (CO₂-eq) emissions and real travel times (RTT) from door-to-door of FGEA on 47 routes with existing aircraft, train and car transport modes, as well as with proposed high-speed rail (HSR) and electric vehicle implementation. The study found that replacing all existing aircraft with FGEA can clearly be recommended as it would result in a reduction of CO₂-eq emissions and RTT. Existing cars should only be replaced by FGEA on routes beyond 170 km. The replacement of existing trains by FGEA under the current energy mix is not recommended. However, once electricity could be provided from renewable energy sources exclusively, it would become feasible to replace existing trains on distances beyond 170 km and HSR beyond 400 km with FGEA.     

The greenhouse gas mitigation potential of university commuting: A case study of the University of León (Spain)

This work analyzes the main drivers and critical aspects of mobility at the University of León (ULE) in Spain and its potential for mitigation of greenhouse gases (GHG). Through the implementation of a life cycle analysis (LCA) methodology (door-to-door and well-to-wheel approach), we examine the existing relationships between modal distribution, distances, travel times, urban structure, and direct and indirect carbon footprint and monetary costs of ULE users' commuting to its premises. Necessary primary information was collected by means of an online survey conducted on all ULE bodies and actors. Even though most distances traveled to the University are of <6 km (94.3% of the commutes), the use of the private car is second in importance (34%) after traveling by foot (41.5%), as well as the main hotspot in environmental terms (95% of GHG emissions). The results show how university policies focused on improving mobility habits (greater use of bus, bicycle and walking) can considerably reduce GHG emissions within a distance range of 0–6 km. For instance, the replacement of cars with bicycles (50% in <4 km distances) would reduce CO₂-eq emissions by 17.5% and increase monetary savings by 14.8%. However, 5.8% of the remaining travels (> 6 km) accumulate 49.4% of the emissions. Beyond that distance, behavior-oriented policies prove to be insufficient, and actions and measures at other levels encouraging technological change (use of electric cars and bicycles, etc.) and the improvement of infrastructures are also required. This article discusses the role of universities in promoting improvement of sustainable mobility within its premises.     

The spatial externalities of car-based worktravel emissions in greater London, 1981 and 1991

This research considers vehicle emissions from travel to work trips by car within and through the localities of London. Specific focus is placed on the residential origins of the trips and the analysis is based on 1981 and 1991 Census travel to work data. London is divided into some 24 one kilometre concentric ring bands and the number of vehicle kilometres travelled within each of these is calculated from ward to ward origin-destination worktravel movements by car. The spatial distribution of vehicle emissions from the perspective of the source origin of this type of urban environmental external disbenefit is derived. The research points to the highest concentrations of emissions located firmly in the centre of the city and this confirms scientific survey evidence of air quality. The results also confirm that in Central and Inner London the largest proportionate contribution to total emissions arises from vehicles originating from residences in Outer London.     

Will new technology be sufficient to solve the problem of air pollution caused by Swedish road transport?

In this article, levels of future specific vehicle emissions and the energy efficiency required to match long-term environmental targets are estimated. The possibility of reaching these targets is also evaluated. It appears to be possible to achieve sufficiently large reductions in both nitrogen oxide (NO_x) and non-methane volatile organic compound (NMVOC) emission to meet long-term Swedish environmental requirements even with continuing transport growth. Combining sufficiently large carbon dioxide reductions with transport growth seems to be more difficult and would require major breakthroughs regarding drive systems, materials and vehicle construction. Such technological developments cannot, however, be entirely ruled out.     

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.     

Environmental benefits of air–rail intermodality: The example of Madrid Barajas

The environmental impact of transport is a growing issue in transport infrastructure planning. The construction of a high-speed rail station at the Madrid Barajas Airport in Spain is an example of the integration of different transportation modes, with expected environmental benefits. We construct a model to assess modal choice and environmental benefits. The results show that with high-speed rail the number of people choosing air travel and the private car is reduced leading to important environmental benefits: a reduction of close to 5 kg of CO₂ per passenger, or 10% of all emissions on the corridor. Our results also show that increasing the cost of using the private car is picked up by air transport rather than high-speed rail, leading to an increase in total emissions.