Emission Calculation - bellevuewa/BKRCast GitHub Wiki
The emission script originally in Soundcast is now accessible in BKRCast, with adjustments made to emphasize the cities of Bellevue, Kirkland, and Redmond.
The emission calculation comprises three components: emission generated between OD pairs (interzonal), emission generated inside TAZs (intrazonal), and generated during the start-up phase of operation.
https://github.com/USEPA/EPA_MOVES_Model/blob/master/docs/MOVES4CheatsheetOnroad.pdf
Emission Rates
Emission rates utilized in BKRCast were initialliy sourced from Soundcast. Due to the file size limitations on Github, some rates for areas outside of King County were omitted from the original from Soundcast input files. These rates are now stored in running_emission_rates_by_veh_type_bkr.csv and start_emission_rates_by_veh_type.csv. They remain consistent EPA MOVES4 model.
Emission rates are influenced by ambient temperature. Generally, winter emission rates are applied in calculations for pollutants. However, an exception exists for VOCs, for which the summer rate is utilized.
Emission rates are additionally influenced by the vehicle speed, time of day, road way type and vehicle type. In BKRCast, the time period spans more than one hour. To streamline the calculation process, specific hours have been selected to represent each time period.
| TOD | selected hour for emission calculation purpose |
|---|---|
| 6to9 | 7 |
| 9to1530 | 12 |
| 1530to1830 | 17 |
| 1830to6 | 19 |
running_emission_rates_by_veh_type_bkr.csv and start_emission_rates_by_veh_type.csv
| Column | Value | Description |
|---|---|---|
| pollutantID | integer | pollutant ID |
| roadTypeID | integer | 4: urban restricted access; 5: urban unrestricted access; 0: outside of King County. Defined in EPA MOVES4. |
| avgSpeedBinID | integer | speed group in 5 mph interval. See below. Defined in EPA MOVES4 |
| monthID | integer | 1: Jan 7: July |
| hourID | integer | in one hour interval |
| ratePerDistance | float | emission rate per vehicle mile |
| county | King |
|
| veh_type | string | light, medium, heavy, transit |
| year | integer | 2018, 2030, 2040, 2050 |
Pollutant included in the calculation:
| pollutant ID | pollutant name |
|---|---|
| 1 | Total Gaseous HCs |
| 2 | CO |
| 3 | NOx |
| 5 | Methane |
| 6 | N20 |
| 79 | Non-methane HCs |
| 87 | VOCs |
| 90 | Atmospheric CO2 |
| 91 | Total Energy |
| 98 | CO2 Equivalent |
| 100 | PM10 Exhaust |
| 106 | PM10 Brakewear |
| 107 | PM10 Tirewear |
| 110 | PM25 Exhaust |
| 112 | Elemental Carbon |
| 115 | Sulfate Particulate |
| 116 | PM25 Brakewear |
| 117 | PM25 Tirewear |
| 118 | Composite NonECPM |
| 119 | H20 Aerosol |
| 200 | Total PM10 |
| 201 | Total PM25 |
avgSpeedBinID
Interzonal Emission
Emission generated by interzonal trips are calculated by multiplying VMT by speed bin and emission rate. VMT calculation relies on an output file named network_summary.csv, which is generated by scripts/summarize/standard/network_summary.py. This file provides vehicle volume by user class, travel time, facility type (@facility_moves). It is essential to ensure this network summary file is kept up-to-date for accurate calculations.
Intrazonal Emission
Similar to interzonal emission, emission generated by intrazonal trips are also calculated by multiplying VMT and emission rate. Intrazonal VMT calculation requires another output file, 'iz_vol.csv, from network_summary.py` script. This file provides intrazonal volume and intrazonal travel distance.
Intrazonal speed is assumed as speed bin 4 (12.5 ~ 17.5 mph), and all intrazonal roadways are urban streets without restricted access.
Start Emission
Start emission includes the following vehicle types: light vehicle, medium truck, heavy truck and transit vehicle.
Start emission utilizes the total vehicle growth rate between the model year and base year to scale up the base year total vehicle population to the future year. This scaled total vehicle population in model year is then used to calculate start emission. The base year's total vehicle population is defined in the file named vehicle_population_bkr.csv.
Input Files
| File Name | Path |
|---|---|
| bus_vehicles_bkr.csv | inputs\model\emission |
| running_emission_rates_by_veh_type_bkr.csv | inputs\model\emission |
| start_emission_rates_by_veh_type.csv | inputs\model\emission |
| vehicle_population_bkr.csv | inputs\model\emission |
| _household.tsv | outputs/daysim |
| iz_vol.csv | outputs/network |
Outputs
All emission outputs are saved in outputs/emissions/ folder.