It is really important to maintain a space cushion all around your vehicle, especially at high speeds, when things can happen very quickly. You need space in order to react to situations and in order to see situations before it is too late. You should have sufficient space between you and the vehicle in front to stop (2-3 seconds at a bare minimum). You should not drive beside other vehicles, especially large transport trucks and keep out of all other vehicles blind spots and keep them out of your by adjusting speed or even what lane you are in. Not leaving sufficient space would be a major mark.