We consider that you commit to travelling in any chosen vehicle, starting from the moment you confirm the booking by paying the amount for the rental. This step happens right after the owner has accepted your request. We then send you an email allowing you to "Confirm" or "Cancel" your rental, you will just have to click on the green button to confirm.
You can also either confirm or cancel your requests by logging in to your profile, in the section 'My trips'
The confirmation implies a payment in one or two installments.