Develop an easy to use interface

Provide a step-by-step flow that user can solve answering to questions
Reduce as much as possible the number of steps to activate or use the service (possibly around 3/5 steps including payment)
Include visual aids to provide a direct estimation of the order/trip price
Provide a completion bar to show the % or number of steps remaining to place an order, to help people not familiar with apps reducing anxiety and uncertainty.