1. Modelling Motor Vehicle Emissions
The Applications of
EMFAC in Hong Kong
Mobile Source Emission Group
Environmental Protection Department

2. Run-down of the Workshop
9:00 – 9:30 Registration
9:30 – 10:00 Guideline on Modelling Vehicle
Emissions, and
EMFAC-HK
10:00 – 10:15 Tea Break
10:15 – 1:00 Demonstration
Questions and Answers

3. Purpose of the Workshop
- To explain the background of developing the Guideline on Modelling Vehicle Emissions;
- To demonstrate the applications of the Guideline in local EIAs.

4. Background The existing practice:
- Making reference to the vehicle tailpipe emission database in MOBILE; and
Having regard to the local motor vehicle emission control measures;
Working out a common set of fleet averaged vehicle emission factors for the whole Hong Kong.

5. Background
Vehicle tailpipe emissions are sensitive to driving patterns (In EMFAC, they are characterized by average vehicle speeds), ambient conditions, etc.
A common set of fleet averaged vehicle emission factors irrespective of driving patterns - no longer accepted by advanced countries like the EU and the USA.

6. Guideline on Modelling Vehicle Emissions
- To help EIA consultants to come up with a suitable set of project specific fleet averaged vehicle emission factors;
- Not binding on EIA consultants;
- EIA consultants free to adopt it or otherwise;
- Deviations from the Guideline acceptable if there are good justifications.

7. Guideline on Modelling Vehicle Emissions
For RSP, NOx, CO and VOCs:
- EMFAC-HK
For SOx and lead.:
- Mass-balance equation (Ref.: USEPA’s PART 5 Model).

8. EMFAC-HK
Adopted from California Air Resources Board’s EMFAC2002 with modifications to cater for local factors such as local vehicle fleet characteristics.
Alternatives are USEPA’s MOBILE6, MOVES, EU’s COPERT and German Swiss Handbook

9. EMFAC-HK Key features of modelling methodology:
based on driving patterns characterized by average vehicle speeds;
taking into account vehicle emission design technologies and vehicle emission deterioration rate;
other local factors.

10. EMFAC-HK
The model is a tool for estimating project specific fleet averaged vehicle emission factors and vehicle emission inventories for the following primary pollutants:
hydrocarbons (TOG, THC, VOC/ROG, CH4)
　carbon monoxide (CO)
　nitrogen oxides (NOx)
　particulate matters (PM10 & PM2.5)　

11. EMFAC-HK Modelling the following tailpipe emissions: Running exhausts;
　Starting exhausts (for petrol vehicles only).

12. EMFAC-HK Supporting Data for Modelling
Engine-specific;
Local fleet composition and characteristics;
Project specific (traffic pattern, ambient conditions).

13. EMFAC-HK Supporting Data - Engine Specific
Zero mile emission factors (ZMEF) – hard-coded in the model and provided in the graphic user interface (GUI) in the form of different technology group indexes for selection (Appendix III of the Guideline);
Engine emission deterioration rates (DRs) – hard-coded in the model.

14. EMFAC-HK Supporting Data - Local Fleet Specific
Vehicle age distribution for each vehicle class (the existing one posted on EPD’s website);
Annual mileage distribution vs. vehicle age (a set of default distribution is provided in the model);
Daily trips per vehicle (for petrol vehicles only; hard-coded in the model);
Distribution of high emitters vs. vehicle age (hard-coded in the model)

15. EMFAC-HK Supporting Data – Project Specific (I)
Fleet composition in respect of emission control design standards and the retrofit of after-exhaust treatment devices for each model year (first registration year) – existing distribution posted on EPD’s website;
Diurnal variation of vehicle kilometer travelled (VKT); and
Diurnal variation of total daily trips (to be explained in the examples)

16. EMFAC-HK Supporting Data – Project Specific (II)
Distribution of VKT fractions for each average speed bin;
Ambient temperature and relative humidity.

17. EMFAC-HK Project Specific Input Data Diurnal Variation of VKT
Site-specific figures should be used whenever available.
In the absence of site specific figures, they can be estimated based on the traffic data in the Annual Traffic Census (ATC) Report of the Transport Department for roads bearing similar road traffic pattern.

18. EMFAC-HK Project Specific Input Data VKT Distribution for Vehicle Speed Bins
References:
Speed vs. volume/capacity ratio (like those published in Comprehensive Transport Study, CTS-3, report) diurnal variation of traffic flow from ATC
Posted speed limits on roads obtained from Highway Department

19. EMFAC-HK Project Specific Input Data VKT Distribution for Vehicle Speed Bins
Mandatory requirements:
Maximum speed for buses and goods vehicles > 5.5 tonne is 70 km/hr.

20. EMFAC-HK Project Specific Input Data VKT Distribution for Vehicle Speed Bins
For peak hour
Roads with similar traffic patterns; or
Average vehicle speeds can be estimated from speed vs. volume/capacity ratio.

21. EMFAC-HK Project Specific Input Data VKT Distribution for Vehicle Speed Bins
For non-peak hour,
Can be estimated from roads with similar traffic patterns
Average vehicle speeds can be estimated from speed vs. volume/capacity ratio, or
Average vehicle speeds can be taken to be the same as the speed limits of the concerned roads (for speed limit > 50 km/hr)

22. Link Speed Flow Curves

23. Link Speed Flow Curves (CTS-3)
Road Type Vf Vu V1 Vm X Y Z
Rural Road A 60 55 35 22
0.4
1.0
1.2
Rural Trunk Road 75 70 45 30
Urban Local Distributor 12 5
0.1
Urban District Distributor 40 11
Urban Primary Distributor 50 27 16
0.2
Urban Trunk Road
Expressway 90 85 65

24. EMFAC-HK Project Specific Input Data Ambient Temperature & Relative Humdities
At least one year of recent hourly ambient temperature and relative humidity data.
Obtained from Hong Kong Observatory representative data - from a weather station either nearest or having similar characteristics as the study area;
90% valid data in the data set.

25. EMFAC-HK Others
Delete the Inspection and Maintenance Option in the model.
The Guideline may be reviewed from time to time. Reference should be made to the latest version.

26. Thank you!!