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- How do road grade, road type and driving aggressiveness impact vehicle fuel consumption? Assessing potential fuel savings in Lisbon, PortugalPublication . Faria, Marta; Duarte, Gonçalo; Varella, Roberto A.; Farias, Tiago; Baptista, PatriciaThe transportation sector contributes significantly to energy consumption with inherent consequences in terms of emission of local pollutants, which is associated with air quality deterioration. Considering that driving behavior significantly influences fuel consumption, this work goal was to assess how driving aggressiveness is influenced by the type of road and by the road grade, and consequently their impacts on fuel consumption. For that purpose, 47 drivers were monitored in the Lisbon Metropolitan Area during 6 months, allowing building an extensive 1 Hz real world driving database (similar to 33,000 trips, totalizing 28.9 million seconds). This database provided distinctive and representative data, allowing assessing the impacts on fuel consumption rates. Results showed that both road context and aggressive driving behavior impact fuel consumption rates significantly. However, for non-aggressive driving behavior fuel consumption rates increased more with road grade increments (up to 3 times) than for aggressive driving behavior (up to 2.3 times). Furthermore, this study results demonstrated that aggressiveness influences fuel consumption differently across road grades. Aggressiveness impacts are higher for lower road grades, with increased fuel consumption rates by up to 255%. The key findings associated to this research work are that aggressiveness on roads with lower grades tends to correlate with higher percent increase on fuel consumption for all speed ranges. Moreover, aggressiveness seems to correlate with higher fuel consumption on urban streets. Consequently, a reduction in driving under these conditions can offer significant savings in fuel consumption.
- Engine cold start analysis using naturalistic driving data: City level impacts on local pollutants emissions and energy consumptionPublication . Faria, Marta; Varella, Roberto A.; Duarte, Gonçalo; Farias, Tiago L.; Baptista, PatriciaThe analysis of vehicle cold start emissions has become an issue of utmost importance since the cold phase occurs mainly in urban context, where most of the population lives. In this sense, this research work analyzes and quantifies the impacts of cold start in urban context using naturalistic driving data. Furthermore, an assessment of the influence of ambient temperature on the percentage of time spent on cold start was also performed. Regarding the impacts of ambient temperature on cold start duration, a higher percentage of time spent on cold start was found for lower ambient temperatures (80% of the time for 0 °C and ~50% for 29 °C). Results showed that, during cold start, energy consumption is >110% higher than during hot conditions while emissions are up to 910% higher. Moreover, a higher increase on both energy consumption and emissions was found for gasoline vehicles than for diesel vehicles. When assessing the impacts on a city perspective, results revealed that the impacts of cold start increase for more local streets. The main finding of this study is to provide evidence that a higher increase on emissions occurs on more local streets, where most of the population lives. This kind of knowledge is of particular relevance to urban planners in order to perform an informed definition of public policies and regulations to be implemented in the future, to achieve a cleaner and healthier urban environment.
- Driving for decarbonization: Assessing the energy, environmental, and economic benefits of less aggressive driving in Lisbon, PortugalPublication . Faria, Marta; Duarte, Gonçalo; Varella, Roberto A.; Farias, Tiago; Baptista, PatriciaThis work assesses the impacts of aggressive driving behavior on pollutants emissions and energy consumption at a city level. Furthermore, it performs an economic analysis considering the potential avoided emissions and fuel savings and discusses potential policy measures to address this topic. The results showed that aggressive driving significantly impacts energy consumption and emissions, with energy consumption increasing by more than similar to 200% and emissions by 330% for aggressive driving compared to non-aggressive driving (in MJ/km and in g/ km, respectively). This increment was found to be even higher for diesel vehicles than for gasoline vehicles. On the contrary, gasoline vehicles showed higher percentages of increase for most emissions (CO, NOx and NO). Results also revealed that aggressive driving impacts are higher for local streets when examining the city level. Moreover, the economic analysis showed that significant cost reductions may be achieved by avoiding aggressive driving, reaching up to 52.5 k(sic) on a daily basis. In conclusion, this study is of particular relevance to policy makers and urban planners, enabling to obtain a comprehensive overview of the impacts of aggressive driving behaviors at a city level and providing new insights to perform further developments and to assess the feasibility of the implementation of policy measures.
- Assessing the influence of boundary conditions, driving behavior and data analysis methods on real driving CO2 and NOx emissionsPublication . Varella, Roberto A.; Faria, Marta; Mendoza-Villafuerte, Pablo; Baptista, Patricia; Sousa, Luís; Duarte, GonçaloThe need to verify vehicle emissions in real world operation led to the implementation of Real Driving Emissions (RDE) test procedures, effective since September 2017 for new Euro 6 cars following the Commission Regulation (EU) 2016/427, which defines the RDE test conditions and data analysis methods to allow representative results. Main factors addressed by the regulation include the share of driving operation, ambient temperature range, altitude and elevation difference. However, RDE is still debatable since not only boundary conditions but also the evaluation methods and trip selection are being discussed together with a carbon dioxide (CO2) regulation, which is planned to be implemented in the short term. Thus, this work focuses on analyzing the effect of different data measurement and analysis methods (i.e. cold operation, road grade, trip selection and driving style) on CO2 and nitrogen oxides (NOx) emissions based on 13 RDE tests performed in the Lisbon Metropolitan Area, Portugal. The tests were conducted by 2 drivers using 5 vehicles. Each driver performed 2 trips per vehicle, one in normal driving and other in aggressive driving. A Portable Emissions Measurement System (PEMS) was used to collect 1 Hz data, which was compared and analyzed using the European Commission (EC) proposed method for RDE tests. Results show the effects of each parameter such as average difference between drivers (7% in CO2 and 55% in NOx emissions) and between aggressive and normal driving. For road grade, big oscillations happen during the slope profile, which impacts emissions during all trips. Considering cold-operation, CO2 and NO emissions are, on average, similar to 25% and 55% higher, respectively, than in hot-operation. These results highlight the need for deeper studies on these factors to assure that RDE tests evolve to a more established certification procedure than laboratorial certifications. (C) 2018 Elsevier BM. All rights reserved.