Under what circumstances would the customer be charged two single trips vs. one return trip?

If the waiting time between the outbound and return leg of the trip is more than 3 hours, then it will be classed and charged, likely by separate Cab providers as 2 separate trips, which we call a 'split trip'. The customer could, in theory, have each leg of the trip weeks apart but the advantage of this approach is it minimises the need for the Customer to repeat the process of booking 2 trips if the pickup and final drop off points are the same e.g. if a family is booking a trip to a holiday destination, and want to be collected a week later.