It's a whole lot easier to bill a flat trip charge...
And then a pmh rate from the time the truck comes to a complete stop at the customer's property.
For example I simply charge a flat $xx amount to come out, same amount, every customer, regardless of distance(s), every time.
Once I arrive at the customer's house the clock starts and a separate pmh rate gets tacked on top of the trip charge.
When I am done working the clock stops, and the amounts totaled.
Otherwise you'll drive yourself nuts with lunch breaks and gas stations, etc.
Which would also explain how that $20-$24 pmh might be a lot higher, such as when you don't have traffic lights figured in.
Unless I misunderstood what you were doing...