I charge for travel generally. I recommend that the client cut down my travel by giving me PCAnywhere access. If they want me on site, they can pay for me to get there. There is one case when I don't charge - since I choose to live an hour from a major city and I am competing with consultants in the metro area, I will sometimes charge from the time I reach the city limits until I leave them again. My advice is, plan to charge for it, and if the client doesn't like it and you can afford to be negotiated out of it, trade for some other benefit.