I do like meliftman's company does.
The difference is that I don't charge the customer for travel time but for the distance covered. Inside the price of one kilometer I have all my expenses covered including my time (calculated on 80 km/h average basis).

Also before, thank god, I was never called out after hours.
Once I left the workshop it's over for the day. I used to work almost all Saturdays, but when I was free I was never called out. That's really stressful.