Would you expand on this?
I make it apparent to the homeowner when they are interfering with the production, for both of our sakes.
I started off based on a spreadsheet I made using a TCIA guide for estimating your hourly cost. Basically you take your annual expense and divide it by your annual billable hours, and you have a beak even cost. Add profit, and you have a goal hourly rate.
For the mileage I initially took added up all of my fixed vehicle related expenses and divided them by estimated annual mileage. Then I figured out the cost per mile of fuel for each truck. Then I figured out the cost per mile of labor based on an average wage at an average speed such as 30 or 40 MPH.
Initially I came up with $1.25/passenger, and $2.00/driver and truck. It worked on an all day job, but when we had more than one job I was missing my daily goal because of the lower mobilization rate. I upped the rate to $1.50/passenger, $2.50/chip truck and driver, $3.00 bucket truck and driver. So for example, google maps says job site is 12 miles from "home" I double that for roundtrip and we have 24 miles. I need a 3 man crew with both trucks onsite. We have $7.00/mile x 24 miles = $168 mobilization charge. That same charge for just the two trucks with drivers, and no 3rd man would be 24 miles x $5.50 / mile = $132.
On long trips I can come down a little since our average speed usually increases, but then we often have to deal with traffic so I might not lower it. On the other hand, when I'm going a couple miles down the road I still charge $30-50 minimum since there is loadup time etc that needs to be factored in. Kinda discretionary.
When I got started I was bidding mobilization time based on time at hourly standard rates. It seems like it's easier for customers to understand it based on mileage for some reason, and they don't feel like I'm charging them for traffic. Unless it's time and materials I don't disclose my mobilization rates. I have not had a complaint about the charge. Well maybe once, and she complained about a minimum charge too, even though her work exceeded it. Some people just complain...
The goal initially was to cover cost, not necessarily making profit on the mobilization time. That way I knew cost was covered, and it helped with bidding competitively on long drives into other markets (30-60 mins 1 way). Then I reconsidered and while we don't necessary make the same profit on mobilization time, we generally still do make some, and it's a buffer for traffic etc.