I am using average-speed emission functions for NOx which are reported in the UK national atmospheric emission inventory. I am using these, alongside traffic flow and speeds data I got from elsewhere, to calculate vehicle emissions across a city and then simulate dispersion.
My understanding is that these functions (in the UK NAEI) are sourced from COPERT 4 (version 10.0).
We would like to better understand the data underlying the functions and as I could not find a clear documentation of that, I am looking for any documentation/experiences that may help answer my queries below:
- What is the data underlying the curves/functions development? (laboratory measurements, PEMS, remote-sensing, modelled emissions, a mix of what exactly??)
- How well do the reported curves fit the data? (do you report a measure of goodness of fit or error somewhere)
- How was the averaging done so as to come up with the data points underlying the curves/functions? (speed and emission rates averaged over a trip? Over a defined time period? Or traveled distance?)
- Is there a relation between COPERT and the instantaneous emission model PHEM?
I would very much appreciate your help with this.
Interesting question, been around for 12 days without an adequate response. I really cannot help you either, but you may want to check out a few contacts from this site (link). The developers of the emission database HBEFA checked their model in the context of what has been around at the time. Maybe, they can give you a pointer towards the underlying data/functions. Good luck with your search!
http://www.hbefa.net/e/index.html
Thanks Ingo. I have also sent a few emails to COPERT developers but still no news. Will post the answer if I get it. Thanks for the direction.
Hi Haneen,
Your question is a very interesting and valid one. I've come across several references in the past dealing with the questions you've just pointed out. Here are some examples that could be a good starting point for you:
- Kousoulidou et al., 2013: Use of portable emissions measurement system (PEMS) for the development and validation of passenger car emission factors.
- Borge et al., 2012: Comparison of road traffic emission models in Madrid (Spain).
- Kioutsioukis et al., 2010: Uncertainty and sensitivity analysis of national road transport inventories compiled with COPERT 4.
- Smit et al., 2010: Validation of road vehicle and traffic emission models – A review and meta-analysis.
This is there official reference of the COPERT methodology, in case you haven't come across it yet.
http://www.eea.europa.eu/publications/emep-eea-emission-inventory-guidebook-2009/part-b-sectoral-guidance-chapters/1-energy/1-a-combustion/1.a.3.b-road-transport-gb2009-update.pdf
Hope this helps,
Michel
Hi, some answers and a document I received from the model's developers. Answers some of the queries but not all. Please do share your thoughts here. Cheers, Haneen
• What is the data underlying the curves/functions development? (laboratory measurements, PEMS, remote-sensing, modelled emissions, a mix of what exactly??)
Old (pre Euro 4) emission factors in COPERT are based on laboratory measurements over real-world cycles, like Artemis, Modem, BAB, etc. These cycles have been split in subcycles and average emission levels per subcycle have been associated with mean subcycle speed.
What is the definition of a subcycle here?
New (post Euro 4) ones are based on regressions over the HBEFA driving cycles. These have been developed by using laboratory measurements as an input to a virtual vehicle model, which is then run over specific driving patterns. In this sense, Euro 6 and 6 emission factors are based on synthesized information over real-world driving patterns.
You may find some more information in the COPERT version reports, at http://emisia.com/products/copert-4/versions.
No PEMS data have been used yet – although we are in the process of start using them at a Euro 6 level. Remote sensing data have been used for validation of emission factors but in next COPERT versions, we may start using them to deliver degradation functions with mileage.
Unfortunately, it is not possible to deliver more specific information as this is largely case-specific and vehicle-specific. I should clarify that COPERT has been developed using results of several projects over the years so, depending on what one is looking for (hot, cold start, evaporation, fuel effects, etc.) and vehicle category, the underlying dataset may vary.
• How well do the reported curves fit the data? (do you report a measure of goodness of fit or error somewhere)
You may find attached a report where uncertainty of emission factors is provided. This corresponds to an earlier COPERT version but you do get a feeling of the order of magnitude per pollutant.
• How was the averaging done so as to come up with the data points underlying the curves/functions? (speed and emission rates averaged over a trip? Over a defined time period? Or travelled distance?)
I guess I have responded to you on this previously. You may also see attached an overview of the process so you better understand. I think this will also explain your next question.
• Is there a relation between COPERT and the emission model PHEM developed by Graz?