Once I noticed that reports in Synchro and Simtraffic about emissions are very diferent, so today I made an simple experiment. I made 3 legs unsignalized intersection with no traffic on minor street ant free traffic on major street (no turn traffic). Eastbound volume was 500 vph, Westbond volume was 500 vph. I compared results of synchro measures of effectiveness report and simtraffic measures of effectiveness report (1 hour recording). There are results:

Synchro

Volume (vph): EBT-500, WBT-500
Total traveled time (hr): EBT-4, WBT-4
Distance trveled (km): EBT-215, WBT-184
Fuel consumed (l): EBT-20, WBT-18
CO emissions (kg): EBT-0.38, WBT-0.33
NOx emissions (kg): EBT-0.07, WBT-0.06

Simtraffic

Vehicles entered: EBT-515, WBT-503
Travel time (hr): EBT-5.0, WBT-4.2
Travel dist (km): EBT-219.2, WBT-184.8[/B]
Fuel used (l): EBT-198.5, WBT-176.4
[B]CO emissions (g): EBT-2042 (2.04 kg), WBT-1928 (1.98 kg)
NOx emissions (kg): EBT-24, WBT-20

Is there software bug? or I don't understand properly? Could someone help me?

Hi Marius,

This isn't really a software bug but more of a limitation to the methods and to differences in the models. First, the way that emissions are determined is very different between the models. Synchro is a simplfied equation. SimTraffic uses emission rate and fuel consumption tables. Then, each individual vehicle is measured and summed at the end. This value in SimTraffic will change based on your recording interval (Synchro is 1 hour).

SimTraffic also captures the delays, fuel and emissions that are missed by macro models. The big one would be when vehicles are blocking each other in turn pockets.

Always think of fuel and emission measures as relative to other alternatives. Do not rely on the absolute values.

We would really like to find better models for this. However, we have found little concensus on the best methods out there for this. We'd like to implement models that have wide-spread approval.... I just don't know if this is possible. Any suggestions from users is appreciated.

Thanks,

John.