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As type approval driving cycles were found to be insufficient to represent the real impact of emissions from on-road vehicles, it became clear that real-driving emissions must be considered to effectively address the current transportation challenges. The expected introduction of on-board emission monitoring is believed to require tools that will evaluate the on-road emissions conformity of vehicles over their lifetime. In this regard, the significant amount of data made available from modern vehicles opens for improved emissions prediction and diagnostics opportunities. This article explores therefore the effectiveness of predicting instantaneous engine-out N O x emissions given in-service vehicle data alone. To this end, a 9 months daily vehicle usage database was used to calibrate and evaluate a semi-empirical N O x emission model and the results showed good agreement with measurements provided by the production sensor. This approach offers a tool for simulating real-driving engine-out N O x emissions that could help to comply with emission standards by feeding and updating advanced emissions control strategies. [ABSTRACT FROM AUTHOR]

With a strong legal basis and regulatory authority, cost-effective transient emission sensors that reflect real-driving emissions are key factors for accomplishing environmental requirements. It is difficult for the existing NOx emission monitoring techniques to achieve a balance between accuracy and timeliness. Fundamentally, in-cylinder combustion is the thermodynamic cause of NOx emissions and the main excitation source for engine vibration and noise emissions. A novel vibration-based virtual NOx sensor is developed based on these critical relationships for real-time NOx monitoring. First, the correlation between vibration and NOx emission was characterized in-depth. Then, a technique of constructing two-dimensional filters for vibration signals is proposed to extract combustion-related information. A principal component regression (PCR) model for NOx prediction was established based on the reconstructed in-cylinder pressure. Finally, the virtual NOx sensor is tested and validated on a single-cylinder diesel engine bench. The virtual NOx sensor is proven to meet the accuracy requirement of vehicle emission monitoring for both steady-state and transient conditions and has a better frequency response compared to the emission measurement system. [ABSTRACT FROM AUTHOR]

In the pursuit of policies and regulations on real-world driving emissions, it becomes necessary to quantifiably define what constitutes “real-world driving.” Measurements of ambient temperature, pressure, and humidity can be used to quantify the weather. Routes can be quantified by their fixed characteristics such as length, road grades, and speed limits. Variable traffic conditions can be quantified by the number of traffic encounters, the number of traffic stops, the fraction of traffic limited driving, et cetera. A real-world drive cycle arises from the interactions between the driver, weather, route, and traffic. People sometimes colloquially described drive cycles in terms of aggressiveness. This subjective characteristic of aggressiveness is here quantified using dynamics metrics, and it is discussed how such metrics could be used by researchers and regulators. A new dynamics metric, the average judicative element, is presented in this investigation. This new metric is compared to previously developed metrics, and its advantages and disadvantages are considered. It is argued how the average judicative element is a superior aggressive-dynamics metric for characterizing drive cycles in scientific studies and governmental regulations.

With a strong legal basis and regulatory authority, cost-effective transient emission sensors that reflect real-driving emissions are key factors for accomplishing environmental requirements. It is difficult for the existing NOx emission monitoring techniques to achieve a balance between accuracy and timeliness. Fundamentally, in-cylinder combustion is the thermodynamic cause of NOx emissions and the main excitation source for engine vibration and noise emissions. A novel vibration-based virtual NOx sensor is developed based on these critical relationships for real-time NOx monitoring. First, the correlation between vibration and NOx emission was characterized in-depth. Then, a technique of constructing two-dimensional filters for vibration signals is proposed to extract combustion-related information. A principal component regression (PCR) model for NOx prediction was established based on the reconstructed in-cylinder pressure. Finally, the virtual NOx sensor is tested and validated on a single-cylinder diesel engine bench. The virtual NOx sensor is proven to meet the accuracy requirement of vehicle emission monitoring for both steady-state and transient conditions and has a better frequency response compared to the emission measurement system.

Based on a large number of test data obtained from real driving emission test of gasoline vehicles, the emission performance of vehicles with different technique route under real driving conditions were studied, the emission sensitivities and feasible schemes to meet the China 6 RDE standards for vehicles with different technologies were also evaluated. It is revealed that for the tested fleet covering different emission control technologies and under current proposed RDE limit, the passing rate can reach 72% at the initial implementation stage of China 6 standard, and increased to more than 85% after more than one year of China 6 standard implementation, the main failure cause were the over standard emission of PN; the RDE pollution control level of domestic brands is equivalent to that of the foreign brands, but there is a certain gap between WLTC pollution control level; adding GPF is a relatively safe technology to deal with PN emission both in on road RDE tests and laboratory WLTC tests, and vehicles with additional coated GPF can obtain relatively better NOx emission performance.

The Euro 7 standard is expected to intensify its focus on real-driving emissions compliance thanks to the on-board monitoring (OBM) system. OBM is designed to bridge the gap between emission limits and real-world vehicle emissions by continuously monitoring their levels using on-board sensors and models. Essentially, this system aims to verify vehicles compliance, prompt timely repairs otherwise, and provide authorities with emissions data for fleet inspection. Leveraging a large real-driving emissions database from an in-service Euro 6d-Temp vehicle, this paper reviews the current OBM proposal and discusses its possible outcomes and challenges using available sensor technology. • The Euro 7 on-board monitoring concept is reviewed and discussed. • On-board monitoring emissions assessment is analyzed with real-driving data. • Challenging aspects regarding the correct emissions estimation are highlighted. • More than 60% of the NOx trip information can be lost due to sensor light-off delay. [ABSTRACT FROM AUTHOR]

Recent recommendations given by WHO include systematic measurements of ambient particle number concentration and black carbon (BC) concentrations. In India and several other highly polluted areas, the air quality problems are severe and the need for air quality related information is urgent. This study focuses on particle number emissions and BC emissions of passenger cars that are technologically relevant from an Indian perspective. Particle number and BC were investigated under real-world conditions for driving cycles typical for Indian urban environments. Two mobile laboratories and advanced aerosol and trace gas instrumentation were utilized. Our study shows that passenger cars without exhaust particle filtration can emit in real-world conditions large number of particles, and especially at deceleration a significant fraction of particle number can be even in 1.5–10 nm particle sizes. The mass concentration of exhaust plume particles was dominated by BC that was emitted especially at acceleration conditions. However, exhaust particles contained also organic compounds, indicating the roles of engine oil and fuel in exhaust particle formation. In general, our study was motivated by serious Indian air quality problems, by the recognized lack of emission information related to Indian traffic, and by the recent WHO air quality guidance; our results emphasize the importance of monitoring particle number concentrations and BC also in Indian urban areas and especially in traffic environments where people can be significantly exposed to fresh exhaust emissions. [Display omitted] • Real-world particles emissions of passenger cars were studied down to 1.5 nm • Nanoparticle emissions were detected especially at deceleration conditions • Black carbon emissions were detected especially at accelerations • Chemical composition of particles revealed the roles of fuel and engine oil [ABSTRACT FROM AUTHOR]

Abstract Hybrid electric vehicles (HEVs) are perceived to be more energy efficient and less polluting than conventional internal combustion engine (ICE) vehicles. However, increasing evidence has shown that real-driving emissions (RDE) could be much higher than laboratory type approval limits and the advantages of HEVs over their conventional ICE counterparts under real-driving conditions have not been studied extensively. Therefore, this study was conducted to evaluate the real-driving fuel consumption and pollutant emissions performance of HEVs against their conventional ICE counterparts. Two pairs of hybrid and conventional gasoline vehicles of the same model were tested simultaneously in a novel convoy mode using two portable emission measurement systems (PEMSs), thus eliminating the effect of vehicle configurations, driving behaviour, road conditions and ambient environment on the performance comparison. The results showed that although real-driving fuel consumption for both hybrid and conventional vehicles were 44%–100% and 30%–82% higher than their laboratory results respectively, HEVs saved 23%–49% fuel relative to their conventional ICE counterparts. Pollutant emissions of all the tested vehicles were lower than the regulation limits. However, HEVs showed no reduction in HC emissions and consistently higher CO emissions compared to the conventional ICE vehicles. This could be caused by the frequent stops and restarts of the HEV engines, as well as the lowered exhaust gas temperature and reduced effectiveness of the oxidation catalyst. The findings therefore show that while achieving the fuel reduction target, hybridisation did not bring the expected benefits to urban air quality. Graphical abstract Unlabelled Image Highlights • Two pairs of HEVs and ICE vehicles were tested in a novel convoy mode using PEMS. • Both HEVs and ICE vehicles had higher RDE fuel consumption than laboratory results. • HEVs saved 23%–49% fuel relative to their ICE counterparts in real-driving. • HEVs showed no reduction in HC and consistently higher CO compared to ICE vehicles. [ABSTRACT FROM AUTHOR]

Abstract Remote sensing provides a rapid detection of vehicle emissions under real driving condition. Remote sensing studies showed that diesel nitrogen oxides emissions changed little or were even increasing in recent years despite the tightened emission standards. To more accurately and fairly evaluate the emission trends, it is hypothesized that analysis should be detailed for individual vehicle models as each model adopted different emissions control technologies and retrofitted the engine/vehicle at different time. Therefore, this study was aimed to investigate the recent nitric oxide (NO) emission trends of the dominant diesel vehicle models using a large remote sensing dataset collected in Hong Kong. The results showed that the diesel vehicle fleet was dominated by only seven models, accounting for 78% of the total remote sensing records. Although each model had different emission levels and trends, generally all the dominant models showed a steady decrease or stable level in the fuel based NO emission factors (g/kg fuel) over the period studied except for BaM1 and BdM2. A significant increase was observed for the BaM1 2.49 L and early 2.98 L models during 2005–2011, which we attribute to the change in the diesel fuel injection technology. However, the overall mean NO emission factor of all the vehicles was stable during 1991–2006 and then decreased steadily during 2006–2016, in which the emission trends of individual models were averaged out and thus masked. Nevertheless, the latest small, medium and heavy diesel vehicles achieved similar NO emission factors due to the converging of operation windows of the engine and emission control devices. The findings suggested that the increasingly stringent European emission standards were not very effective in reducing the NO emissions of some diesel vehicle models in the real world. Graphical abstract Image 1 Highlights • Hong Kong diesel vehicle fleet was dominated by a few models in each class. • Each diesel vehicle model showed very different NO emission levels and trends. • Largest NO increase attributed to change from indirect to direct injection engines. • All the latest diesel vehicle models achieved similar NO emission levels. • Euro standards failed to reduce NO emissions of some models during specific stages. The European emission regulations were not very effective in reducing the NO emissions from some diesel vehicle models in the real world. [ABSTRACT FROM AUTHOR]

Motivated by the fact that the real driving NOx emissions (RDE) of conventional diesel vehicles can exceed the legislation norms by far, a concept for the control of RDE with a diesel parallel hybrid electric vehicle (HEV) is proposed. By extending the well-known equivalent consumption minimization strategy (ECMS), the power split degree of freedom is used to control the NOx emissions and the battery state of charge (SOC) simultaneously. Through an appropriate formulation of the problem, the feedback control is shown to be separable into two dependent PI controllers. By hardware-in-the-loop (HIL) experiments, as well as by simulations, the proposed method is shown to minimize the fuel consumption while tracking a given reference trajectory for both the NOx emissions and the battery SOC.

Tests with Portable Emissions Measurement Systems (PEMS) have demonstrated that diesel cars emit several times more NO X on the road than during certification on the New European Driving Cycle (NEDC). Policy makers and scientists have attributed the discrepancy to the unrealistically low dynamics and the narrow temperature range of NEDC testing. Although widely accepted, this assumption was never been put under scientific scrutiny. Here, we demonstrate that the narrow NEDC test conditions explain only a small part of the elevated on-road NO X emissions of diesel cars. For seven Euro 4–6 diesel cars, we filter from on-road driving those events that match the NEDC conditions in instantaneous speed, acceleration, CO 2 emissions, and ambient temperature. The resulting on-road NO X emissions exceed by 206% (median) those measured on the NEDC, whereas the NO X emissions of all unfiltered on-road measurements exceed the NEDC emissions by 266% (median). Moreover, when applying the same filtering of on-road data to two other driving cycles (WLTP and CADC), the resulting on-road NO X emissions exceed by only 13% (median) those measured over the respective cycles. This result demonstrates that our filtering method is accurate and robust. If neither the low dynamics nor the limited temperature range of NEDC testing can explain the elevated NO X emissions of diesel cars, emissions control strategies used during NEDC testing must be inactive or modulated on the road, even if vehicles are driven under certification-like conditions. This points to defeat strategies that warrant further investigations by type-approval authorities and, in turn, limitations in the enforcement of the European vehicle emissions legislation by EU Member States. We suggest applying our method as a simple yet effective tool to screen and select vehicles for in-depth analysis by the competent certification authorities. [ABSTRACT FROM AUTHOR]

In this paper we present the results corresponding to on-road traffic emissions measurements obtained during two field campaigns developed in the Madrid region (Spain) during 2014 and 2015 in the framework of the CORETRA project. The experimental strategy was based on the use of a RSD 4600 remote sensor in interurban roads. These measurements have produced a global database of > 190,000 vehicles with their associated emission data (NO/CO 2 , HC/CO 2 and CO/CO 2 ), which can be considered representative of the current Spanish circulating fleet. The results of M1 vehicles were analysed according to their distribution by Euro Standard and engine model. One of the relevant findings is that, despite the progressive introduction of increasingly stringent standards, no NO emission reduction is observed for diesel vehicles with time, although this behavior shows significative differences among brands and engine models. We have also investigated the presence of “high emitter” (HE) vehicles in the Spanish M1 circulating fleet and most of the HE detected corresponded to diesel vehicles with very high NO/CO 2 values. With these results at hand, we strongly propose the future incorporation of the “high emitter vehicle” definition into the European environmental legislation, as well as the establishment of specific strategies in each country/region in order to identify these anomalous vehicles. Identification and repair of HE vehicles within the European circulating fleets, although are not easy tasks, should be considered very important for the improvement of air quality in the EU. The use of non-intrusive optical technologies (i.e. RSD) is an excellent option to provide instantaneous real emission data of each individual vehicle without disturbing traffic and for on-road fleet monitoring. In summary, it is a good strategy to obtain valuable information about the long term surveillance of real vehicle emission trends, specially after the introduction of new standard. [ABSTRACT FROM AUTHOR]

Motivated by the fact that the real driving NOx emissions (RDE) of conventional diesel vehicles can exceed the legislation norms by far, a concept for the control of RDE with a diesel parallel hybrid electric vehicle (HEV) is proposed. By extending the well-known equivalent consumption minimization strategy (ECMS), the power split degree of freedom is used to control the NOx emissions and the battery state of charge (SOC) simultaneously. Through an appropriate formulation of the problem, the feedback control is shown to be separable into two dependent PI controllers. By hardware-in-the-loop (HIL) experiments, as well as by simulations, the proposed method is shown to minimize the fuel consumption while tracking a given reference trajectory for both the NOx emissions and the battery SOC. [ABSTRACT FROM AUTHOR]

Tests with Portable Emissions Measurement Systems (PEMS) have demonstrated that diesel cars emit several times more NO X on the road than during certification on the New European Driving Cycle (NEDC). Policy makers and scientists have attributed the discrepancy to the unrealistically low dynamics and the narrow temperature range of NEDC testing. Although widely accepted, this assumption was never been put under scientific scrutiny. Here, we demonstrate that the narrow NEDC test conditions explain only a small part of the elevated on-road NO X emissions of diesel cars. For seven Euro 4-6 diesel cars, we filter from on-road driving those events that match the NEDC conditions in instantaneous speed, acceleration, CO 2 emissions, and ambient temperature. The resulting on-road NO X emissions exceed by 206% (median) those measured on the NEDC, whereas the NO X emissions of all unfiltered on-road measurements exceed the NEDC emissions by 266% (median). Moreover, when applying the same filtering of on-road data to two other driving cycles (WLTP and CADC), the resulting on-road NO X emissions exceed by only 13% (median) those measured over the respective cycles. This result demonstrates that our filtering method is accurate and robust. If neither the low dynamics nor the limited temperature range of NEDC testing can explain the elevated NO X emissions of diesel cars, emissions control strategies used during NEDC testing must be inactive or modulated on the road, even if vehicles are driven under certification-like conditions. This points to defeat strategies that warrant further investigations by type-approval authorities and, in turn, limitations in the enforcement of the European vehicle emissions legislation by EU Member States. We suggest applying our method as a simple yet effective tool to screen and select vehicles for in-depth analysis by the competent certification authorities., (Copyright © 2016 The Authors. Published by Elsevier Ltd.. All rights reserved.)