Some designers do charge for travel time, and 50% of the hourly fee is normal. Personally, I invoice only when I leave Manhattan, never within Manhattan. Why? Primarily I have two things to sell: talent and time. Both have value; and talent/time not expended on project work impacts everyone negatively, including you. Projects that do not run smoothly are not time/cost efficient and end up costing everyone more money. If I’m concerned about other issues and am hampered in my ability to achieve resolution, I cannot focus fully on your project! Further, if I’m in the subway I may have limited access to cell service. If I’m on a train I may not be able to speak freely or at length or there may be line interference; and it may be a situation where texting and emailing will not suffice. If I’m driving, I shouldn’t be on the phone at all! Think of it this way: an hour or more each way to/from your home and three hours on your job site fills most of a work day. It’s time dedicated to you and no one else. If that’s not valuable to you, then you may be working with the wrong designer.