Non-exhaust traffic related emissions – Brake and tyre wear PM

Traffic related sources are a significant contributor of particulate matter, particularly in urban environments and major cities. Traffic related particles can be distinguished into: exhaust traffic related particles, which are emitted as a result of incomplete fuel combustion and lubricant volatilization during the combustion procedure, and non-exhaust traffic related particles, which are either generated from non-exhaust traffic related sources such as brake, tyre, clutch and road surface wear or already exist in the environment as deposited material and become resuspended due to traffic induced turbulence. It is estimated that exhaust and non-exhaust sources contribute almost equally to total traffic-related PM10 emissions. However, as exhaust emissions control become stricter, relative contributions of non-exhaust sources to traffic related emissions will increasingly become more significant. The aim of the present literature review study is to present the state-of-the-art of the different aspects regarding particulate emissions resulting from non-exhaust sources and particularly from brake and tyre wear. For this reason several different literature sources such as peer reviewed papers, research project reports, technical publications, as well as licentiate and doctoral theses were examined and the most significant findings in terms of importance, physicochemical characteristics, EFs and possible adverse health effects are discussed.JRC.F.8-Sustainable Transpor

Brake wear particle emissions: A review

Traffic related sources have been recognized as a significant contributor of particulate matter particularly within major cities. Exhaust and non-exhaust traffic related sources are estimated to contribute almost equally to traffic related PM10 emissions. Non-exhaust particles can be generated either from non-exhaust sources such as brake, tyre, clutch and road surface wear or already exist in the form of deposited material at the roadside and become resuspended due to traffic induced turbulence. Among non-exhaust sources, brake wear can be a significant PM contributor, particularly within areas with high traffic density and braking frequency. Studies mention that in urban environments brake wear can contribute up to 55% by mass to total non-exhaust traffic related PM10 emissions and up to 21% by mass to total traffic related PM10 emissions, while in freeways this contribution is lower due to lower braking frequency. As exhaust emissions control become stricter, relative contributions of non-exhaust sources - and therefore brake wear - to traffic related emissions will become more significant and will raise discussions on possible regulatory needs. The aim of the present literature review study is to present the state-of-the-art of the different aspects regarding PM resulting from brake wear and provide all the necessary information in terms of importance, physicochemical characteristics, emission factors and possible health effects.JRC.F.8 - Sustainable Transpor

Analysis of WLTP typical driving conditions that affect non-exhaust particle emissions

Driving conditions have a large influence on particle generation from brake and tyre wear processes. Different driving conditions in experimental investigation of particle emissions from brake and tyre wear is one of the reasons why different - or even sometimes- contradictory conclusions are reported. In order to harmonize future studies on particles from brake and tyre wear and improve the comparability of the relative results, the definition of “normal” or “typical” driving patterns has been identified by PMP group as an important working item. The proposed approach is to use activity data collected in the framework of other projects in order to investigate typical acceleration / deceleration frequency distributions. The main objectives of this activity are to compare “typical/normal driving conditions” derived by existing datasets like the WLTP vehicle activity database with the industry standards, as well as to reach, if possible, a shared definition of normal, severe, extreme or infrequent conditions. This will narrow down the range of driving conditions to be taken into consideration as far as non-exhaust particle emissions are concerned and will improve the comparability of future studies. This report describes the results of a detailed analysis of the WLTP in-use database. The results are provided in this report and in dedicated ACCESS databases.JRC.C.4-Sustainable Transpor

Assessment of the Heavy-Duty Natural Gas technology

Heavy Duty Vehicles (HDV) powered by Compressed Natural Gas (CNG) are seen as a possible option for curbing CO2 emissions, fuel consumption and operating costs of goods transport. CNG engines have been employed in public use HDVs as an alternative to diesel engines due to their environmental benefits, and particularly due to lower particulate matter (PM) and nitrogen oxides (NOx) emissions. In the framework of the current project, an advanced newly designed CNG prototype engine developed as part of the 7th Framework Programme research project “CO2 Reduction for long distance transport” (CO2RE), is benchmarked against its parent Euro V compliant CNG engine (reference) in order to quantify the improvement in terms of real-world emissions. Results indicated a significant reduction in CO2 emissions with the prototype CNG engine both at low and high loads, which varied between 5.0-8.4%. The highest CO2 reduction was observed during on-road testing, with the corresponding reduction at low loads being more pronounced compared to high loads. Furthermore, reductions of NOx and CO emissions were observed under all testing conditions. On the other hand, hydrocarbon and methane emissions were increased with the introduction of the Prototype engine.JRC.F.8-Sustainable Transpor

Particle Number (PN) - Portable Emissions Measurement Systems (PEMS): Heavy Duty Vehicles Evaluation phase at the Joint Research Centre (JRC)

JRC evaluated the feasibility of using PN-PEMS systems for Heavy Duty Vehicles (HDV) applications. The main evaluation phase took place between February and June 2016. One Compressed Natural Gas (CNG) vehicle and three vehicles equipped Diesel Particulate Filters (DPF) and Selective Catalytic NOx Reduction (SCR) were tested. The key conclusion of the evaluation phase is that PN-PEMS testing for HDV is feasible. However, low ambient temperatures were challenging for the instruments regarding their robustness. Re-testing of the commercial instruments in September with a DPF and SCR equipped vehicle showed that most of the issues were resolved. The PN-PEMS instruments measurement uncertainty is around 30% at the moment. Similar uncertainty (35%) was found when comparing the best performing system with the reference system at the dilution tunnel (CVS); i.e. PEMS method uncertainty.JRC.C.4-Sustainable Transpor

Assessment of the monitoring methodology for CO₂ emissions from heavy duty vehicles: Pilot phase test-campaign report and analysis of the ex-post verification options

Following a request from DG-Clima and DG-GROW, JRC launched a test-campaign in order to investigate the validity, accuracy and plausibility of the methodology proposed for the verification of the certified CO2 emissions from Heavy Duty Vehicles (aka ex-post verification methodology). In addition scope of the test campaign was to demonstrate the representativeness of the CO2 emissions calculations made by the official simulator (VECTO) by comparing against the actual performance of vehicles. Experiments were conducted on four Euro VI trucks, both on the chassis dyno and on the road with the aim of understanding the advantages and disadvantages of different approaches proposed. Two main verification approaches were investigated, steady state measurements in chassis-dyno / controlled conditions, and measurements under transient conditions on chassis-dyno and actual on-road operating conditions. The official simulation software (VECTO) was used for simulating the operation of vehicles under the different test conditions. The key conclusion of the test campaign is that an ex-post verification method which is based on transient, on-road tests is possible for trucks and comes with the advantage that it could potentially cover also other vehicle types which are difficult to be validated under steady state conditions in a laboratory or on a test track under controlled conditions. However, there is a clear need to work on the details of the test protocol to be finally implemented, define boundary conditions for transient tests on road, and establish the necessary acceptance and rejection margins for any such validation. Finally, additional testing is necessary in order to calculate accurately any systematic deviation between the officially reported, simulated, CO2 values and those actually occurring in reality. VECTO results should be periodically controlled and assessed in order to make sure that its CO2 estimates remain representative and minimize the possibility that discrepancies will occur in the future between the officially reported and actually experienced fuel consumption.JRC.C.4-Sustainable Transpor

Development of Heavy Duty Vehicles CO2 certification for Heavy Buses and Medium Lorries

In 2019, a Verification Test Procedure (VTP) – to be applied randomly on complete vehicles after the certification processes – became a part of the HDV CO2 Certification Regulation (EU/2019/318). The VTP consists of an on-road test to verify the CO2 emissions of new vehicles after production. At the same time, a new regulatory initiative aiming at the certification of the FC from HDVs not covered in EU/2017/2400 was initiated. The new methodology will also include a VTP test; however, adapted for vehicle categories such as Heavy Buses and Medium Lorries. In this framework, DG-GROW requested JRC to launch a test campaign to investigate the validity, accuracy, and feasibility of the proposed methodology for these vehicle categories. Experiments were conducted on four Euro VI HDVs; two Heavy Buses and two Medium Lorries. All on-road tests proved to be highly repeatable with the SE for the WSFC not exceeding 2%. Both Coaches showed a quite good agreement between the measured and simulated WSFC with the deviation not exceeding 5.5%. Medium Lorries exhibited a different behaviour mainly due to the overestimation of the electrical power demand of auxiliaries by VECTO in the VTP Mode. Overall, a less transient route, similar to the regulated, seems more appropriate for the VTP of Coaches. On the other hand, a more transient route might be more suitable for the VTP of Medium Lorries. Increasing the payload from 60% to 80% does not seem to affect the test repeatability. The CVTP for both vehicles fulfilled the pass criterion defined in 2019/318 for Heavy Lorries in all 14 tests. The FC data were analyzed to understand the suitability of different instruments to provide accurate FC measurements. The FC calculated from the PEMS CO2 emissions is generally close to the reference FFM FC with the averaged deviation not exceeding 4% in the vast majority of the tests. The ECU FC seems to be slightly less accurate compared to the PEMS FC. Both PEMS and ECU seem to perform equally well both under non-transient and highly transient conditions. Finally, one of the goals of the study was to collect experimental data of pollutant emissions during the VTP test. NOx emissions were generally low and did not exceed the EURO VI engine certification limit (0.46 g/kWh). The more transient routes exhibited higher NOx emissions pointing to a less effective operation of the catalyst under these conditions. CO emissions were generally low and well below the EURO VI engine certification limit (4.0 g/kWh).JRC.C.4 - Sustainable Transpor

Brake Wear Particle Emissions of a Passenger Car Measured on a Chassis Dynamometer

Brake wear emissions with a special focus on particle number (PN) concentrations were investigated during a chassis dynamometer measurement campaign. A recently developed, well-characterized, measurement approach was applied to measure brake particles in a semi-closed vehicle setup. Implementation of multiple particle measurement devices allowed for simultaneous measurement of volatile and solid particles. Estimated PN emission factors for volatile and solid particles differed by up to three orders of magnitude with an estimated average solid particle emission factor of 3∙109 # km−1 brake−1 over a representative on-road brake cycle. Unrealistic high brake temperatures may occur and need to be ruled out by comparison with on-road temperature measurements. PN emissions are strongly temperature dependent and this may lead to its overestimation. A high variability for PN emissions was found when volatile particles were not removed. Volatiles were observed under high temperature conditions only which are not representative of normal driving conditions. The coefficient of variation for PN emissions was 1.3 without catalytic stripper and 0.11 with catalytic stripper. Investigation of non-braking sections confirmed that particles may be generated at the brake even if no brakes are applied. These "off-brake-event" emissions contribute up to about 30% to the total brake PM10 emission

Estimating the CO2 Emissions Reduction Potential of Various Technologies in European Trucks Using VECTO Simulator

Heavy-duty vehicles (HDVs) account for some 5% of the EU’s total greenhouse gas emissions. They present a variety of possible configurations that are deployed depending on the intended use. This variety makes the quantification of their CO2 emissions and fuel consumption difficult. For this reason, the European Commission has adopted a simulation-based approach for the certification of CO2 emissions and fuel consumption of HDVs in Europe; the VECTO simulation software has been developed as the official tool for the purpose. The current study investigates the impact of various technologies on the CO2 emissions of European trucks through vehicle simulations performed in VECTO. The chosen vehicles represent average 2015 vehicles and comprised of two rigid trucks (Class 2 and 4) and a tractor-trailer (Class 5), which were simulated under their reference configurations and official driving cycles. The effects of aerodynamics, auxiliary systems, curb-weight, tyre rolling resistance, engine internal losses, and engine and gearbox efficiency were investigated. Factors exhibited a varying reduction potential that depended on the vehicle category and the driving cycle. Results indicate where focus should be given for improving the energy performance of trucks in view of the Commission’s future efforts to propose CO2 reduction targets for HDVs.JRC.C.4 - Sustainable Transpor

Study of brake wear particle emissions of a minivan on a chassis dynamometer

Car brakes appear to be a significant atmospheric pollutant source, with a contribution to total non-exhaust traffic-related PM10 emissions being estimated at approximately 55% in big cities and urban environments (Bukowiecki et al., 2009). Brake wear particle emissions of a minivan running on a chassis dynamometer were measured using a custom sampling system, positioned close to the braking system, under different initial speeds (30 km/h and 50 km/h), deceleration rates (0.5 m/s2, 1.5 m/s2, 2.5 m/s2), and ambient temperatures (0 °C, 15 °C and 25 °C). Braking from 50 km/h to full stop, results in 40–100% more particles compared to 30 km/h, depending on the deceleration rate. It was also found that only 9–50% of the total particles emitted, are released during the braking phase and therefore the most significant amount is released on the following acceleration phase. High brake pad temperature results in a bimodal distribution with the first peak being at 1 μm and the second falling at the nanometer scale at 200 nm. The ambient temperature appears to have a negligible effect on the particle generation. Document type: Articl