We handle travel time in one of two ways, depending on the distance and associated estimated travel time. The base is 1/2 the hourly rate, one way. So basically 1/4 of the time spent traveling. The other is to specify a minimum number of hours billed for on site visits, usually 2. Both of these are typically never questioned by the clients, so figure out which one is most beneficial to you, and go with that one.
For out of town travel, we bill actuals for airfare, hotel room, rental car, and a per diem (meals and incidentals) based on what GSA allows https://www.gsa.gov/travel/plan-book/per-diem-rates This is all spelled out in the SOW or Master Services Agreement. We give our guys the per diem and they can choose to do whatever they want. So they will typically eat fast food and pocket the rest. Provide the actuals for the airfare hotel and car when you make the reservations or before the the reservations are booked if they seem expensive for whatever reason.