 One rule of thumb is to allow at least one second for each 10 feet of vehicle length at speeds below 40 miles per hour. At greater speeds, add an additional second. It's impossible to keep other drivers from tailgating you, but there are some things you can do to make it safer, such as increasing your following distance, avoiding quick lane changes, and slowing down. There are also several things you should do to ensure that there is plenty of space between the side of your vehicle and other vehicles.