I charge an additional fee for travel over 15 minutes one way (ie. if it takes me 15 minutes to get there and 15 minutes to get home, no fee). The fee is whatever portion of an hour or more multiplied by my regular fee for the type of training that I will be doing. I can’t train anyone during the time that I must travel to and from, so that is part of the time spent on training them.
I always quote the fee up front based on an estimate of the time I will travel. And if I find the time is less, I reduce the cost. If it is longer, I charge more and they know this is the deal going in.