I have a very specific question about fasting. I am a travelling salesperson. My daily average mileage is about 150 miles. During Ramadan, I have no problem keeping my fast and doing my normal routine - currently our fasts are about 19 hours, but I am still able to cope. However on a regular basis, I have to travel further and my daily drive can become closer to 300 miles or more, sometimes I am aware of the fact that I have a long journey, sometimes as the day progresses, I find myself further and further away and then have a long drive back home. Generally when I know I have a long drive, I do not keep a fast on that day, but what happens if my day starts with a fast, and then I find I am many hundred miles away, tired, even exhausted. Is it permissible for me to break my fast and what then do I have to do?