Correct, I did not correctly interpret the question. However, if you portray someone who is moving into the area nd making a special trip for apartment/house hunting, calling ahead by even a couple of days and stating that arrival time will depend on traffic/road conditions, should help in your scenario.
I also try to start calling a week (or more) in advance. (For an apartment this is completely normal for a prospective resident moving from out-of-state to call the leasing office well in advance of a visit for appointment.
I have had a few times when I could not get the target on my routes and the scheduler has ALWAYS been understanding about.
In terms of scheduling myself, I categorize my shops in terms of geographical locations and "flexible v. "not-flexible" visit times. I get the "not-flexible" times set ASAP as they often dictated how many/which other shops I can take on my routes.
MFJ, you said it all much better than I.
I was not being snide; I really thought that you provided a more cogent explanation than I did. Good on you !