http://www.tunnels.mottmac.com/news/?id=26278

http://www.tunnels.mottmac.com/tunnelsexpertise/tunnelventilationandaerodynamics

http://www.mottmac.com/skillsandservices/software/stepssoftware


additional stuff from Mott Macdonald:

http://www.tunnels.mottmac.com/downloads/presentations

http://www.tunnels.mottmac.com/downloads/papers

Hi all,
I just want to say that data from FDS about fire can be imported in the new version of STEPS. I am testing the results between some scenarios with fire simulated with STEPS and with FDS+Evac. I will tell you my results. It is very interesting to check the differences in the results using models based in different approaches (i.e. some models consider FED values and others the effect of visibility in wayfinding).

Thanks,

This is a new and important feature to have. STEPS, in my opinion, is one the best models.

I think comparison between models is very important; and more studies should be conducted though.

regards,

Rodrigo

Hi all,

I'm new to the application of evacuation models, I'm currently studying STEPS and I'd like to ask you a clarification about the setting of the number of runs to be performed for a given scenario.
How can I choose a proper number of runs, mainly when using distributions?

Thank you in advance!
Regards
maria grazia

Hi Maria,

The reason many evacuation models produce different results for repeating exactly the same scenario is because random numbers are used somewhere in the model. This is typically done when either a process is not well understood e.g. conflict resolution when 2 agents compete for the same location, or , gaining a value from a probability distribution e.g. response time range. As such, the number of runs needed will be dependent on the extent these occur and the size/types of distributions used. A sufficient number of runs should reflect a 'suitable' spread of these random numbers about the distributions and the extent that they occur.

One way to give an indication of the level of variability between runs would be to use the change in total evacuation time (TET) between runs. The larger the differences between TET in each run the more that are needed. You could state that enough runs have been performed when the last X runs vary from the average TET by no more than Y%. This method can have problems but it is one way.

I think choosing the number of simulation runs is a bit of a black art and many people just run many simulations to ensure they are representative.

Hope this helps,

Michael

Hi Michael,

thank you so much for your advice!!

Kind regards,
Maria Grazia