Guard your safety by actively creating space around your vehicle, never allowing yourself to get "boxed in." Adequate space creates time and helps you avoid collisions. Maintain at LEAST two seconds of following distance, more if you can. Adjust your position in traffic as necessary to avoid driving in others' blind areas. Don't allow yourself to be tailgated--change lanes or adjust your speed to encourage tailgaters to pass you.
Many of us were taught to use the car-length rule for following distance (one car length for every ten mph). That rule is no longer recommended because car lengths are difficult to visualize, impossible to visualize when moving, and the rule didn't provide enough space in the first place. For example, 6 car lengths at 60 mph provide roughly 108 feet of space. At 60 mph, the average alert reaction time eats 60 to 130 feet (and in the real world, closer to 135 feet for many), leaving little or no time to act. Two seconds of following distance at 60 mph, on the other hand, gives you over 176 feet of pavement to react and respond. Even at two seconds of following distance, you must respond quickly, but it can be done under normal circumstances.
How do you apply the two-second rule? Watch as the vehicle ahead passes some object--I often use shadows or marks on the road surface--then count "one-thousand-one, one thousand two." If you pass that same spot before getting to "two," you're too close--back off!
There ARE times when two seconds isn't enough. Leave more space when you can, and leave additional space if following a vehicle with different characteristics than yours--motorcycles or trucks, for example--or if the road surface is slippery. Motorcycles can often stop faster than you, and trucks (or trailers) impede your vision, which can cause you not to see hazards until too late. Ice can increase your stopping distance many times over, so leave lots of extra space if it might be present. Eight or ten seconds is not unreasonable around ice.
It is an error to think you cannot leave the appropriate space in heavy traffic. Some don't try, because they think other vehicles will change lanes in front of them and fill the space. It is not as common a problem as you probably think, and heavy traffic is one time when you really need the space! If someone cuts into your space, simply back off a little and get it back! Lose the ego--"It doesn't matter"--what counts is your safety. I once counted the number of times other drivers cut in front of me over about fifteen miles of city freeway during rush hour traffic. Over fifteen miles, it only occurred three or four times. I have found that typical, and I use the two-second rule every day with no problems.
Here's a tip--drive a mile or two per hour slower than traffic flow. This doesn't cost any appreciable time, and traffic will be slowly pulling away from you, helping you to maintain the space. If you do this, keep to the right and out of the way for courtesy's sake. In many states, this is a legal requirement when you're driving slower than other traffic.
Pay attention to anyone driving next to your vehicle in other lanes. Adjust your speed to keep your vehicle "in the open," with no vehicles to the left or right, as much as you can. Be very uncomfortable if vehicles are "packed" around you. Traffic tends to move in packs, so watch out and try to occupy the spaces between the packs, so you have clear lanes on both sides. (This is an absolute necessity for motorcyclists!)
It is important to leave space even when stopped for a light. Leave room in front so you can pull away if the car ahead stalls or doesn't move, or if you need to move because of danger approaching from behind. You also don't want to be boxed in and unable to move for personal safety reasons. Stop far enough back so you can see the rear tires of the vehicle in front of you where they touch the pavement--this will give you room to pull out and around when necessary.
Remember, leave yourself an "out!" May all your roads be new, smooth, rubberized asphalt!