Re: [CTPP] A Question - work flow vs. HBW trip rate

Binbin--Elaine's response is certainly dead on but your question prompted a broader discussion that I was having with one of my colleagues. Here what he had to say. Suffice it to say your local model and more importantly your local conditions will play prominently. Ed -- A Work to Home trip would actually be counted as two separate trips -- two HBW productions and two HBW attractions. Using a factor of 1.5, 1,000 employees would generate 1,500 HBW trips; then you'd need to divide by two to approximate a CTPP-derived home-to-work trip, giving you 750 trips. This, of course, presumes that travelers will be making round-trips, when we know that many make stops on the way home from work. Often rules are applied that reallocate a HBW work trip as two distinct NHB trips (e.g. with a stop of more than 30 minutes); some models get around this by specifying trips as a 'journey-to-work', which can include longer duration stops. The use of the 1.5 scaling factor is intended to capture chaining, absenteeism, and should be understood to be a rough approximation that may not accurately reflect local conditions or the labor market. In terms of comparing with the NHTS trip rates, the analyst could impose their own rules in terms of how a HBW trip is defined -- and depending on NHTS sample size for the area considered, a comparison between the two may be meaningful and shed light on adjustments to the factor used to convert flows to trips, thereby producing a more reliable CTPP derived trip-table. Eric eric.pihl(a)dot.gov Binbin Chen wrote: -- Ed Christopher 708-283-3534 (V) 708-574-8131 (cell) FHWA RC-TST-PLN 19900 Governors Dr Olympia Fields, IL 60461