How can I account for travel time without adding it to the service time

I am using appointments+ for a photography website to schedule on-location appointments.

http://promediatours.com/make-an-appointment/

I have no problem with the time allowed for a given service. But I travel to and from each appointment. I need to account for 1/2 hour travel time on either side of any appointment. How can I do that without adding to a service's time?

Thanks for your help.