How to Really Drive On a Highway (in the U.S.)

You've no doubt heard many times that you should drive no faster than the speed limit, leave ample room between your car and the car in front of you, and always drive in the far right lane. The people who say such things have obviously never driven on the highways before. Here's how it works in actual real-life traffic conditions.

About Speed Limits

Every road has a natural speed at which cars naturally want to drive. This speed seldom has any relation to the posted speed limit, and is usually higher. The other cars on the road will have a predictable range of speeds, with approximately 10 mph difference between the slowest and fastest. You should drive within this speed range if you want to avoid being a road hazard to everyone else.

If you're worried about police, just pay careful attention to how fast everyone else is driving. If all other cars on the road have suddenly, inexplicably slowed down, it means there's a police car ahead. Slow down along with everyone else to avoid becoming a target.

Following Room

The official rule of thumb is to have four seconds between you and the car in front of you. That is, there should be a four second gap between the time the car in front of you passes a stationary object (road sign, bridge, etc.), and the time you pass it.

On most actual highways, however, this means you're driving too slowly, and is an open invitation for everyone else on the road to cut you off. Why? A four-second gap is very large, which means everyone will be cutting in front of you. If you attempt to maintain a four-second gap after someone has cut in, you have to slow down. Soon you're moving far slower than everyone else - which makes you a road hazard via getting in the way of natural traffic flow.

Don't bother trying to maintain an officially proper gap. Give yourself enough room if you need to hit the brakes suddenly, but otherwise try to maintain the same bumper distances as other cars around you. If you pay careful attention to the brake lights of the cars in front of you in your own lane, and watch the cars in the lanes to either side, you will have plenty of warning before someone does something unexpected. Cars have body language, even when they aren't using their turn signals. Reading car body language is a learnable skill.

Defining Highway Lanes

A few definitions before we continue. Where I say "cruising lane" below, you may have heard it as "slow lane" or "driving lane." Also, when I talk about number of lanes, what I mean is the number that are going in the same direction. A two-lane is two lanes going one way and two more lanes going the other - usually referred to as a four-lane highway. But when you're actually driving on it, you don't care about those other lanes - the only ones that matter are the ones going your way.

The Slow Lane

If the highway has more than two lanes, the far right lane is never the cruising lane. If it's a three lane or five lane highway, you want to slow-cruise in the middle. On a four lane highway it's the second from the right. On a six lane or greater, third from the right. That's where you want to drive if you're on the slow end of the speed range, and you don't want to pass anyone, ever.

Lanes in General

Now let me expand on the above.

There are four basic types of lanes on any given highway. There's always one for entrances and exits. One for slow drivers. One for fast drivers. One for fast passing. On highways with less than four lanes, some lanes will be more than one type. On highways with more than four lanes, there will be multiple lanes for the same basic purpose.

The Far Right Lane

The rightmost lane has several purposes. It's for people who are entering the highway and merging in, preparing to exit the highway, driving much slower than everyone else (speed limit drivers tend to be here), or driving much faster than everyone else because they're executing a complex right passing maneuver because someone in the far left lane is being slow and oblivious.

Entrances and exits are the main thing, however. On any highway with three or more lanes, you want to reserve the rightmost lane for that purpose. On a two-lane, observant drivers will move over to the left lane as they approach entrance ramps if they see a car coming in. On a highway with five or more, the two rightmost might both be entrance and exit lanes.

Different Speeds in Different Lanes

As a general rule of thumb, slow driving occurs in the right lanes, faster driving occurs in the left lanes. The average cruising speed goes up as you move left. When traffic is heavy, this will include the leftmost lane - which is otherwise mainly for passing. On many highways with four or more lanes, big trucks aren't allowed in the leftmost lane at all.

Notable Exceptions

Then there are the occasional left exits and entrances. And the mountains with steep grades and runaway truck ramps - which can be left or right. If in doubt about where you should drive, try to stay in the middle.