"exclusive bus lanes along with transit signal priority DO reduce travel times as shown in some cities"..... Is just a little vague and a wee bit too "anecdotal" for my professional tastes, as to the causality and/or documented benefits.....would you care to elaborate further?

This would be the question I'd probably be asking you at your interview, back when I hired idealistic young folks, just like you.

Which has the greatest impact on travel times, signal priority/pre-emption (ITS), or an exclusive arterial Bus lane itself, and how much of the travel times savings effect in "some" "cities" is attributed to each of the elements?,

David was a little harsh in his generalization, but for every one like you, who seems genuine and committed to learning your craft, I've seen a dozen planning school graduates, long on planning theory, with all of the new urbanist anecdotal reports of miraculous results, short on data methods and analytical skills to collect data in order to assess or test some of these theories, and with little actual experience of any kind, in the "field".

I am a big proponent of the documented results from some of the signal priority/pre-emption projects, which do have some good results along several corridor in LA where it is in operation. I found almost no net travel time savings on any of the corridors we tested in LA in the 90's from extended systems of arterial HOV lanes. I have nothing that has changed since we did that extensive analysis, including the collection of time and motion data, collected in the field.

There are locations where for purposes of cue bypassing, or egress and departure from high volume stops (like the section of Spring Street in front of LA City Hall) which was the only location, even on the rest of the then "reverse flow" Spring Street arterial bus lane section, where we found any significant "net" operational and/or travel time savings.