[adamjb]

1) How is assignment actually done? i.e given a trip from O to D, how does the model decide which mode to take and which roads/routes to take?

2) How well does it validate? I couldn't find any reference to observed traffic count data anywhere

[dabreegster]

1) Mode choice is fixed, coming from https://www.psrc.org/activity-based-travel-model-soundcast. Next work focus will be on adjusting mode choice when edits make it favorable to bike/walk. Route assignment is mentioned in https://dabreegster.github.io/abstreet/how_it_works.html (documenting all assumptions in an organized way has been really hard). There are score functions in https://github.com/dabreegster/abstreet/tree/master/map_mode... -- they're pretty simple right now.

2) I wrote a bit here: https://old.reddit.com/r/urbanplanning/comments/hdylmo/ab_st... In short, validation is hard, and I'd say I'm a bit understaffed.