Gaseous brake wear emissions from heavy duty and light duty vehicles

Wandera Kisimbiri, Romain Couval, Sophie Haslett, Karine Elihn, Ulf Ulofsson, Sarah Steimer

Exhaust and non-exhaust emissions from road vehicles contribute to the degradation of air quality through release of particulate matter (PM) and gaseous pollutants into the atmosphere. With the goal to quantify gases emitted from brake wear, this study utilizes a high-resolution proton transfer reaction time-of-flight mass spectrometer (PTR-TOF-MS) for measurements.

The dataset provided was collected during a campaign at KTH Royal Institute of Science and Technology from January to April 2025. The study involves laboratory chemical characterization and quantification of gaseous emissions from the vehicle braking process by use of a high-resolution proton transfer reaction time-of-flight mass spectrometer (PTR-TOF-MS). The mixing ratios were calculated using sensitivity calibration factors based on multipoint calibrations from a multicomponent gas-phase standard mixture of 13 VOCs contained in a calibration gas cylinder (Apel Riemer Environmental, Inc.), of nominally 1 ppmv ± 5% of each standard. The particulate matter size distribution was measured using the GRIMM optical particle counter (OPS). Other instruments used to collect data during the campaign include Dekati PM10 Impactor, and Thermocouple.

AtmosphereAerosolsBrake Wear EmissionsChemical Ionization Mass SpectrometryNon-exhaust Emissions

Name

Version

Citation

References

Wandera Kisimbiri, Romain Couval, Karine Elihn, Sophie L. Haslett, Ulf Olofsson, and Sarah S. Steimer (2026). Gaseous brake wear emissions from heavy duty and light duty vehicles

Data description

LOGBOOK

The file Logbook_HDV_LDV_campaign.xlsx provides the chronological record of the experimental campaign, including the date and start time of each experiment, and links individual experimental runs to their corresponding measurement files. Each row corresponds to an individual tribometer test and contains information on the brake pad pin and disc materials, instrumentation used, experimental conditions, test duration, and pre- and post-test masses.

The logbook contains the following information:

1. Test_No Sequential identification number assigned to each experiment.
2. Pin_Mat Material designation of the brake pad pin used in the experiment.
3. Pin_No Identification number of the brake pad pin.
4. Disc_mat Material designation of the disc used in the experiment.
5. Disc_No Identification number of the disc.
6. PM_Instrumentation Particulate matter measurement instruments used during the experiment.
7. Other_instrumentation Other instruments used during the experiment.
8. Air_Inlet Instrument or air supply used to provide air to the tribometer chamber.
9. AirFlow_L_min Airflow through the tribometer chamber in L/min.
10. Date Date on which the experiment was performed.
11. Start_Time_Tribometer Start time of the tribometer experiment.
12. Temperature_C Room temperature recorded during the experiment in °C.
13. RH_percent Relative humidity recorded during the experiment in %.
14. Velocity_m_s Sliding velocity used during the experiment in m/s.
15. Contact_Pressure_Mpa Nominal contact pressure applied during the experiment in MPa.
16. Test_Time_min Test duration in minutes.
17. Test_Time_sec Test duration in seconds.
18. Sliding_Distance_m Total sliding distance during the experiment in m.
19. Pin_Radius_mm Radius of the brake pad pin in mm.
20. Weight_Kg Nominal load applied to the pin in kg.
21. Real_weight_use_Kg Actual load used during the experiment in kg.
22. Real_CP_Mpa Actual contact pressure calculated from the applied load and contact area in MPa.
23. Pin_position_m Pin position on the disc during the experiment in m.
24. RPM Rotational speed of the disc.
25. Pin_i_mass_mg Initial mass of the brake pad pin before the experiment in mg.
26. Pin_end_mass_mg Final mass of the brake pad pin after the experiment in mg.
27. Pin_delta_mg Change in brake pad pin mass during the experiment in mg.
28. Disc_i_Mass_g Initial mass of the disc before the experiment in g.
29. Disc_end_mass_g Final mass of the disc after the experiment in g.
30. Disc_delta_g Change in disc mass during the experiment in g.
31. Comments Additional experimental observations and notes.

The Date and Start_Time_Tribometer fields provide the temporal reference for the experiments. These fields are particularly relevant for relating the thermocouple temperature measurements, which contain elapsed time rather than time of day, to the corresponding experimental period.

Handling missing data in the Logbook
Blank cell = the measurement/data was not recorded.
#VALUE! = a calculated field could not be calculated because the required input, such as contact pressure, was not applicable for that test. For example contact pressure is not applicable for blank tests
#DIV/0! = a calculation error resulting from a formula referencing a blank/non-applicable input cell. For example referencing the contact pressure for blank measurements which is not applicable to blank tests.

PTR-TOF-MS_Final1_HDV_LDV

The dataset consists of CSV files generated and exported from TOFWARE within the Igor Pro environment. It contains measurements of gaseous emissions generated during vehicle braking processes, along with sensitivity calibration data.
Further processing and analysis of the PTR-MS data are presented in the accompanying analysis notebook provided as a zip file.

Each PTR-MS CSV file includes the following columns:

1. Date and Time Timestamps are recorded in local time (UTC+1 or UTC+2). The format follows YYYY-MM-DD HH:MM:SS.
2. Chemical Formulas` Columns representing the identified chemical species, expressed as molecular formulas for the detected compounds. The concentrations are in ions/second.
3. Total Ion Current (TIC) total measured ion signal.

GRIMM

The OPC (GRIMM model 1.108/1.109) measured the particle size distributions in the range of 250 to 32000 nm, classifying particles into 31 stages. The raw data files contain the following columns:

1. Date and Time Timestamps are recorded in local time (UTC+1 or UTC+2). The format follows YYYY-MM-DD HH:MM:SS.
2. Particle size bins contain particle number concentrations for discrete aerodynamic diameter intervals in nanometers (nm). The units are in number concentrations per ml of air

Dekati PM10 Impactor

Dekati PM10 Impactor Filter Masses.csv contains data from Dekati PM₁₀ impactor, which was coupled to the tribometer to collect particles for gravimetric analysis. Note that measurements using the PM10 impactor were only conducted during the 6-hour tests. The filter masses are recorded alongside their respective brake pad materials.

TEMPERATURE

The disc temperature was recorded using a Type K thermocouple (TC Disc) with a sliding electrical contact, measuring the temperature at the disc--pin interface. A second Type K thermocouple (TC Pin) was positioned inside the tribometer chamber without being connected to the pin; therefore, its measurements represent the air temperature inside the chamber.

Temperature measurements are provided for SM-Bus and SM-Truck brake pad materials under mild, medium, and harsh braking conditions, and for LM-Passenger and NAO-Passenger brake pad materials under medium braking conditions.

The thermocouple data contain elapsed time in seconds rather than the actual time of day. To plot the temperature data against the actual time of day, the experimental logbook provided in Excel format is required to identify the exact time at which the sliding contact between the pin and disc was established. This time may differ from the thermocouple recording start time because the thermocouples could have started recording before the tribometer was started and before contact between the pin and disc was established.
The start temperature for each experiment is as recorded in the logbook and as presented in the experiment summary in the temperature files.

The temperature files are named according to the test number, brake pad material, and experimental condition. In the file names, "Low2h.txt" denotes the medium condition, "Mild.txt" denotes the mild condition, and "Harsh.txt" denotes the harsh condition. For example, "Temp_Test52_HDV1_Low2h.txt" corresponds to an HDV1 medium condition test 52. The test number are those reported in the campaign logbook.

The temperature files contain the following information:

1. Start times Start date and time of the temperature recording for each measurement channel, recorded with high time resolution.
2. dt Sampling interval between consecutive temperature measurements, given in seconds.
3. Data Temperature measurements recorded by each thermocouple. The data are provided as numerical values in degrees Celsius.

CODE

Brake-Wear-VOCs-KTH-2024-campaign-Vocus-PTR-1.1.0.ipynb contains analysis code associated with the dataset in a jupyther notebook.

Comments

Specifically, the data was recorded from 11th February 2025 to 1st April 2025 during a campaign at KTH Royal Insitute of Science and Technology. Detailed methodology has been described in our paper titled "Gaseoues Emissions From Heavy Duty and Light Duty Vehicles" in the methodology section of the main text and sections in the Supplimentary Information

Materials Description

HDV represent brake pad materials from Heavy-Duty Vehicles, whereas LDV represent brake pad materials from Light-Duty Vehicles. Within the HDV category, HDV1 corresponds to bus brake pad materials and HDV2 corresponds to truck brake pad materials. Within the LDV category, LDV1 represents low-metallic (LM) brake pad materials, while LDV2 represents non-asbestos organic (NAO) brake pad materials. For consistency, the HDV categories have also been relabeled as SM-Bus (formerly HDV1) and SM-Truck (formerly HDV2), whereas the LDV categories have been relabeled as LM (formerly LDV1) and NAO (formerly LDV2).

Readers should refer to the published article for the complete description of the experimental methodology.

Author Contributions

Wandera Kisimbiri prepared and organized the dataset and performed the data processing and analysis. The other authors aforementioned contributed to the experimental work, supervision, interpretation of the results, and development of the associated study.

Other Contact person

Name: Sarah S. Steimer Email: sarah.steimer@aces.su.se

Acknowledgements

W.K. gratefully acknowledges the support from Athanasia Christou of KTH for setting up and operating the POD tribometer. W.K. also acknowledges Anna Breuninger for assisting with the \ce{PM10} filter sampling.

Project

This project was supported by the Swedish Research Council under the grant number 2023-04363) and the Carl Trygger Foundation (CTS 23:2809).

Publisher

Bolin Centre Database

License

Open Data Commons Attribution License (ODC-By) v1.0

First name

Wandera

Last name or organisation

Kisimbiri

Email address

wandera.kisimbiri@aces.su.se

Address

Department of Environmental Science; Stockholm University

Postal code

SE-106 91

City

Stockholm

Province or state

Stockholm

Country

Sweden

GCMD science keyword

Earth science services > Data analysis and visualization

GCMD location

Continent > Europe > Northern Europe > Scandinavia > Sweden

Dataset language

English

Begin date

2025-02-11

End date

2025-04-01

DOI

Time