How does the WFRC model deal with trip chaining?

Was drafting a blog post on trip lengths vs. trip frequency, and the though struck me:

We know that the evening peak is longer and 'lower' than the morning peak. I think that's because people run errands after work (rather than before work). 

Economically speaking, as congestion worsens, the average amount of distance per unit of time falls. As the cost of that time rises, people travel less. I'm thinking that the way people travel less is by chaining trips together. 

The home to work journey is typically the longest people make. Assuming that journey is the hypotenuse of a triangle, the maximum journey  of chained trips is an equilateral triangle. Given the triangle inequality (the sum of two sides is always greater than the third), the minimum diversion is tiny. Looking at the maximum diversion, the greatest distance from the hypotenuse is radical(3)* the hypotenuse, or about 87% of it. So for any trip up to 87% of the distance of your work trip, it makes sense to chain that trip with the work trip. 

I know the WFRC model has HBW, HBO...but is there a WBO (Work-based other)? Or does that just get rolled into the HBW?