On-road Exhaust Emissions Research Articles

Vehicle Stock Numbers and Survival Functions for On-Road Exhaust Emissions Analysis in India: 1993–2018

Road transport plays a crucial role in sustaining all the personal and freight movement needs of residential, commercial, and industrial activities, and in Indian cities, big and small, vehicle exhaust emissions and dust from vehicle movement on the roads contribute to as much as 50% of particulate matter pollution in a year. Therefore, effective management of vehicle exhaust emissions is vital not only for improving current air quality but also for ensuring the long-term benefits from efforts to reduce air pollution. In the approved clean air action plans for 131 cities under the national clean air program (NCAP), more than 50% of the implementable actions are transport-centric. Having a reliable and replicable vehicle exhaust emissions inventory is essential for effective planning, which can help establish a baseline, support scenario analysis, and allow for tracking progress in the sector. This process begins with accessing accurate vehicle stock numbers, typically obtained from vehicle registration databases, traffic surveys, and other governmental records. Often, in low- and middle-income countries like India, these numbers require extensive data cleaning before they can be used for emissions and pollution analysis. This paper presents a cleaned, open-access vehicle stock database for India and outlines a methodology to build and maintain an in-use vehicle age-mix database for future years. The database covers the years 1993 to 2018 for the entire country and individual states, along with estimates of the age distribution of vehicles using survival functions. By offering a comprehensive and reliable data source, this paper aims to support sustainable national and urban air quality management efforts, helping policymakers and stakeholders make informed decisions to improve air quality and public health.

Characterization of Exhaust CO, HC and NOx Emissions from Light-Duty Vehicles under Real Driving Conditions

On-road exhaust emissions from light-duty vehicles are greatly influenced by driving conditions. In this study, two light-duty passenger cars (LDPCs) and three light-duty diesel trucks (LDDTs) were tested to investigate the on-road emission factors (EFs) with a portable emission measurement system. Emission characteristics of carbon monoxide (CO), hydrocarbons (HC) and nitrogen oxides (NOx) emitted from vehicles at different speeds, accelerations and vehicle specific power (VSP) were analyzed. The results demonstrated that road conditions have significant impacts on regulated gaseous emissions. CO, NOx, and HC emissions from light-duty vehicles on urban roads increased by 1.1–1.5, 1.2–1.4, and 1.9–2.6 times compared with those on suburban and highway roads, respectively. There was a rough positive relationship between transient CO, NOx, and HC emission rates and vehicle speeds, while the EFs decreased significantly with the speed decrease when speed ≤ 20 km/h. The emissions rates of NOx and HC tended to increase and then decrease as the acceleration increased and the peak occurred at 0 m/s2 without considering idling conditions. For HC and CO, the emission rates were low and changed gently with VSP when VSP < 0, while emission rates increased gradually with the VSP increase when VSP > 0. For NOx NOx emission rates were lower and had no obvious change when VSP < 0. However, NOx emissions were positively correlated with VSP, when VSP > 0.

Are internally observable vehicle data good predictors of vehicle emissions?

Scientific research has demonstrated that on-road exhaust emissions in diesel passenger vehicles (DPV) exceeds the official laboratory-test values. Increasing concern about the quantification of magnitude for these differences has meant an increasing use of Portable Emissions Monitoring System (PEMS), but the direct use of Internally Observable Variables (IOVs) can be useful to predict emissions.The motivation for this paper is to develop an empirical approach that integrates second-by-second vehicle activity and emission rates for DPV. The objectives of this research are two-fold: (1) to assess the effect of variation in acceleration-based parameters, vehicle specific power (VSP) and IOVs on carbon dioxide (CO2) and nitrogen oxides (NOx) emission rates; and (2) to examine the correlation between IOV-based predictors of engine load and VSP. Field measurements were collected from four DPV (two small, one medium and one multi-purpose) in urban, rural and highway routes using PEMS, Global Positioning System (GPS) receivers and On-board Diagnostic (OBD) scan tool, to measure real-world exhaust emissions and engine activity data.Results suggest the relative positive acceleration (RPA) and mean positive acceleration (MPA) allowed a good differentiation with respect to route trips. IOVs models based on the product of manifold absolute pressure (MAP) and engine revolutions per minute (RPM), and VSP showed to be good predictors of emission rates. Although the CO2 correlation was found to be good (R2 > 0.8), the models for NOx showed mixed results since some vehicles showed a reasonable correlation (R2 ~ 0.7) while others resulted in worst model predictions (R2 < 0.6).IOVs models have potential to be integrated into vehicle engine units and connected vehicles, for instance, to provide real-time information on emissions rates, but other parameters regarding the thermal management on after treatment system must be included in NOx prediction. This would allow for a better understanding of true physics behind NOx emissions in DPV.

The evaluation of exhaust emission in RDE tests including dynamic driving conditions

Abstract The article presents and discusses the research results on the impact of RDE test dynamic parameters on the emission of selected exhaust components. The measurements were carried out in compliance with the latest legislative procedures applicable to passenger cars. Two passenger cars with similar curb weight, equipped with gasoline engine, were selected for the tests in real traffic conditions. All tests were performed on the same research route, which includes urban, rural and motorway conditions. The obtained results were analyzed of RDE procedure’s requirements and the Euro 6c toxicity standard. Then the values of dynamic parameters of both tests were compared (the vehicle velocity and acceleration product, relative positive acceleration and 95th percentile of V·a+). Their effect on the obtained emission results was determined. As a summary, the correlations between the on-road exhaust emission and dynamic parameters were defined.

RDE-based assessment of a factory bi-fuel CNG/gasoline light-duty vehicle

On-road exhaust emissions of a Euro 5 factory bi-fuel CNG/gasoline light-duty vehicle equipped with the TWC were assessed considering the Real Driving Emissions (RDE) guidelines. The vehicle was equipped with a Portable Emission Measurement System (PEMS) that enabled the measurement of THC, CO, NOx, CO2, and CH4. With respect to the characteristics of the vehicle, the appropriate Worldwide Harmonized Light-Duty Vehicle Test Cycles (WLTC) were selected and based on the requirements of the RDE legislation a suitable route was conceived. In addition to the moderate RDE-based route, an extended RDE-based route was also determined. The vehicle was driven along each defined route twice, once with each individual fuel option and with a fully warm vehicle.RDE routes feature a multitude of new driving patterns that are significantly different to those encountered in the NEDC. However, as these driving patterns can greatly influence the cumulative emissions an insight in to local time trace phenomena is crucial to understand, reason and to possibly reduce the cumulative emissions. Original contributions of this paper comprise analyses of the RDE-LDV local time resolved driving emissions phenomena of a CNG-powered vehicle that are benchmarked against the ones measured under the use of gasoline in the same vehicle and under similar operating conditions to reason emission trends through driving patterns and powertrain parameters and exposing the strong cold-start independent interference of CO and N2O infrared absorption bands in the non-dispersive infrared (NDIR) analyzer. The paper provides experimental evidence on this interference, which significantly influences on the readings of CO emissions. The paper further provides hypotheses why CO and N2O interference is more pronounced when using CNG in LDVs and supports these hypotheses by PEMS tests.The study reveals that the vehicle's NOx real-world emission values of both conceived RDE-based routes when using both fuels are within Euro 5 and type-approval limits. Additionally, the THC and the NMHC emissions of both RDE-based routes using both fuels are within the Euro 5 limits indicating reasonable CH4 emissions. Notable increases above the type-approval and Euro 5 limits appeared in the CO emissions profile when using gasoline, while the CO2 emissions profile expectedly also exceeded the type-approval specifications.

Impact of driving style and road grade on gaseous exhaust emissions of passenger vehicles measured by a Portable Emission Measurement System (PEMS)

Motivated by the upcoming Euro-6c regulation including Real Driving Emissions (RDE), the present study addresses the impact of different driving styles and route characteristics on on-road exhaust emissions. Gaseous emissions of two Diesel test vehicles (Euro-5 and Euro-6) were measured using a Portable Emission Measurement System (PEMS) on an RDE compliant test route.The driving parameters relative positive acceleration (RPA), mean positive acceleration (MPA) and v∗apos95 allowed a favorable classification of different driving styles. The comparison of driving parameters for normal PEMS trips with reference data obtained from the World harmonized Light-duty Test Cycle (WLTC) and from Field Operational Tests (FOT) indicated a good representation of normal driving. Severe driving led to elevated CO2 and NOx emissions as compared to normal trips while CO and HC did not allow a distinct classification of different driving styles.Route characteristics of four different routes were investigated applying the parameter cumulated altitude gain using Google Elevation data. The distance specific NOx emissions were in the same range for trips with comparable driving dynamics on routes with similar cumulated altitude gain. Based on repetitive measurements the road grade was calculated within 100m segments. CO2 and NOx emissions measured by a PEMS showed a linear increase with road grade. Larger emissions at higher road grades could be explained by more frequent high engine load points. In this study cumulated altitude gain and road grade were directly correlated to emissions measured by the PEMS and the step from 0 to 5% road grade led to a CO2 increase of 65–81% and a NOx increase of 85–115%.

Development of On-Road Exhaust Emission and Fuel Consumption Models for Motorcycles and Application through Traffic Microsimulation

This study developed on-road exhaust emission and fuel consumption models for application in traffic microsimulations to estimate motorcycle emissions and fuel consumption in an Asian developing city. The motorcycle onboard measurement system was developed to instantaneously measure and continuously record on-road driving data, including the speed-time profile, exhaust emissions, and fuel consumption per second. The test motorcycle was driven on roads around Khon Kaen City, Thailand, to collect on-road driving data during the morning peak hours for a total of 112 hours. The collected on-road driving data were applied to develop on-road exhaust emission and fuel consumption models using regression analysis. The models were developed with high correlations among the amount of exhaust emissions and fuel consumption and the instantaneous speed and acceleration rate. The developed models were applied with a traffic microsimulation to evaluate the exclusive zone for motorcycles stopping at a signalized intersection. The evaluation results reveal that it could improve the level of intersection service by decreasing travel times, delays, and queue lengths at intersections, as well as by reducing the fuel consumption and emissions of vehicles travelling through intersections compared with these values under the existing conditions.

The On-Road Exhaust Emissions from Vehicles Fitted with the Start-Stop System

The paper describes the influence of the start-stop system on the exhaust emissions and fuel consumption. The tests were performed for two vehicles. The first one was a vehicle designed specifically to operate in city conditions. It was fitted with a gasoline engine of the displacement of 0.9 dm3 and maximum power output of 63.7 kW. The other vehicle was an SUV (Sports Utility Vehicle) fitted with a diesel engine of the displacement of 3.0 dm3. The measurements of the exhaust emission were carried out on the same route under actual traffic conditions. For the tests a portable exhaust emissions analyzer from the PEMS group SEMTECH DS was used (PEMS Portable Emissions Measurement System).

On-road exhaust emission testing

The paper presents the reasons behind on-road vehicle exhaust emission testing. The latest legislation has been presented in the paper applicable in the EU as well as the research potential of the Institute of Combustion Engines and Transport of Poznan University of Technology. The presentation of the results of the on-road tests pertains to passenger vehicles, buses and non-road machinery (construction machinery, tractors) and aircraft. The comparison of the exhaust emissions from different means of transport under real traffic conditions constitutes an important trend included in the normative legislation related to exhaust emissions

The on-road exhaust emissions characteristics of SUV vehicles fitted with diesel engines

The paper presents the results of on-road exhaust emission tests of Sport Utility Vehicles fitted with diesel engines, and a DPF (diesel particulate filter). Under such conditions the authors could determine the actual vehicle emissions. The tests were performed on a road portion of a hundred kilometers or so – these tests provide information on the on-road emissions and are a basis for their ecological evaluation. For the measurement of the exhaust emissions the authors used a portable exhaust emissions analyzer SEMTECH DS by Sensors Inc. The analyzer measured the concentration of the exhaust components at the same time measuring the exhaust mass flow. The measurements of the particulate matter (mass, number and spectral distribution) were done with the use of particle analyzer by AVL and a mass spectrometer by TSI. The obtained data were used to calculate the relations that characterize the influence of the dynamic engine parameters on the exhaust emissions. These properties were taken into account indirectly using the whole range of speeds and accelerations of the vehicle for the preparation of the matrices of the emissions rate. The used data were averaged within individual speed and acceleration ranges thus obtaining the characteristics of the share of operation in individual ranges and the characteristics of the emission matrices of the individual emission components. The above results served for defining of the emission level indicator of the vehicles that can be used for classification of vehicle fleet in terms of their emission level.

On-Road Exhaust Emissions from Passenger Cars Fitted with a Start-Stop System

On-Road Exhaust Emissions from Passenger Cars Fitted with a Start-Stop System