4. 2 hours
If you have to drive on a long trip, get plenty of rest before you leave and plan on stopping every 2 hours.
As a general rule, it is safe to drive for more than 8 hours a day, taking breaks of at least 15 minutes in every 2 hours.
This means that you can drive safely for about 500 miles, without having to worry about external factors such as slow toll traffic, traffic, child travel and fatigue.