Since you’re already using Google Maps, have you looked into their more in-depth API integration which gives you a total logistics solution? You can see demos and learn more about their Transportation API here. Or, there are professional apps like Lepton that are based on Google Maps, with an easy to use interface. Or, apps like Routific have their own mapping. Routific starts at just $39/mo. per vehicle so they’re not too costly to try out.
I hope this information helps!