Notes

Despite the advantages of expressways, high-speed driving poses complex risks that you need to be aware of:

Braking distances are longer
Your field of vision is narrowed
Highway hypnosis and velocitation often occur
Two vehicles may attempt to move into the same lane simultaneously
Vehicles may drive in a pack or cluster
Speeding may leave you with insufficient following distance

Large vehicles can block your vision
The effect of being distracted (e.g., by disabled vehicles or billboards) is amplified
Wind and other weather conditions become more dangerous
Wet surfaces can result in hydroplaning
The frequency of entrance and exit ramps in cities can pose hazards

On expressways, speed limits are typically between 60 and 75 mph, although they may be lower in urban areas where more traffic is entering and exiting the expressway.
Remember, the Basic Speed Rule prohibits operating a vehicle at a speed greater than is safe under prevailing traffic and road conditions, regardless of the posted speed limit. On expressways, it's especially important to abide by this law.


Careful observation of signs, signals, and roadway markings is critical when traffic is moving at high speeds.

Speed limit signs and laws are easy to understand, yet speeding violations represent a disproportionately large percentage of total citations. Watch for minimum speed limit signs, as driving too slowly can be especially dangerous on an expressway.
Green guide signs indicate route directions and distances to specified destinations. Within a mile of an exit, three signs will be posted so drivers wishing to exit will have enough time to prepare.
Mile markers help you keep track of the distance traveled and identify when you're nearing your destination.

Shield-shaped interstate signs indicate the number of the expressway you're using so you can identify your position on a map or in an emergency.

North/south routes have odd numbers while east/west routes have even numbers.
Most routes use two-digit numbers.
Alternate routes use three-digit numbers. If the first digit is even, the route goes around the city. If odd, the route goes through the city.

While collisions tend to occur on high-speed expressways less frequently than they do on other roadways, they often have severe consequences due to the higher speeds involved.
According to the NHTSA, while less than 10% of all vehicle collisions that occurred in 2013 took place on roads with speed limits of 60 mph or higher, 21% of all fatal collisions took place on these roadways.


Remember these strategies for reducing risks on an expressway:

Stay alert and know when you are approaching your exit.
Adjust your vehicle's position and speed to compensate for road and weather conditions.
Steer as gently as possible at higher speeds.
Don't change lanes without signaling and checking for an open gap. If you have to change lanes, change one lane at a time.
Never park, back up, or stop on the expressway. Stop on a shoulder only in an emergency.
Make room for vehicles entering traffic from an entrance ramp.
Increase your following distance when behind a truck, bus, or motorcycle.
At higher speeds, search 20 to 30 seconds ahead of you to compensate for the speed at which visual cues are coming.

A number of features are employed on modern expressways to reduce the chance of a deadly impact when a car drives off of the roadway.
The first goal of these design features is to reduce the risk that vehicles will leave their lane and drift into oncoming traffic or off the roadway. The second goal is to reduce the severity of a crash if a vehicle does drift out of its lane.


Wider lanes and shoulders give drivers extra space to navigate.
Most expressways are divided by concrete or cable barriers so that cars can't cross the center of the roadway into oncoming traffic.
Guardrails are used on roadsides to keep drivers from driving off the roadway, especially in places like mountains where no shoulder is available.


Bridges and bridge supports are constructed to support more weight and make it less likely that cars will drive over the side of the bridge.
Light poles, signs, trees, and other obstructions have been removed from the roadside, making it less dangerous to drive onto the side of the road.
Breakaway support posts ensure that traffic signs will not cause severe damage or injuries.

Raised rumble strips and lane reflectors alert inattentive or drowsy drivers when they veer out of their lane or off the road.
Liquid- or sand-filled drums are placed in front of some road barriers to decrease the severity of collisions with these barriers.
Protected merge lanes provide extra protection for drivers maneuvering across traffic.
Clearer signage standards ensure that road signs can be understood quickly and at a distance.
Electronic message signs allow drivers to anticipate specific situations.


To allow vehicles to move from one road to another without crossing streams of traffic, highways and expressways frequently come together at multi-level junctions known as Interchanges.


Cloverleaf Interchange

A cloverleaf interchange allows traffic to flow between two crossing expressways without having to stop or turn. It consists of eight ramps (four are looped and four are curved).
The ramps require drivers to slow down to a safe speed. Reflector poles posted on the ramps help drivers navigate through the curves.

Diamond Interchange

A diamond interchange is used to connect a major expressway with a secondary road with less traffic. Traffic signal lights on the secondary road are often used to control access to the entrance and exit ramps.
A typical diamond interchange uses four directional ramps for entering and exiting.


Trumpet Interchange

A trumpet interchange is a T-intersection where an expressway comes to an end at an intersection. Trumpet interchanges allow traffic to transition smoothly between a secondary, two-way street and the major roadway while keeping the flows of traffic separate.


Frontage Road Interchange

A frontage road is a secondary road that runs parallel to an expressway to allow dense flows of city traffic to mix efficiently with traffic on the expressway. At these interchanges, it's easy for a driver to get back on the expressway, in the same direction or the opposite direction, soon after exiting it.


Because it involves rapidly merging with traffic already moving at high speeds, entering an expressway can be especially difficult—and dangerous. For novice drivers, the prospect of joining such a fast-moving stream of traffic, often from a stopped position, can be a stressful one.
Entering an expressway doesn't have to be difficult. As long as you pay attention, signal your intentions, adjust your speed appropriately, and maintain a safe space around your car, you should always be able to merge with high-speed traffic safely.


Before entering an expressway, pay attention to road signs indicating the route number and direction of the road to make sure you're entering at the right place.
Frequently, there will be entrances to the opposite sides of the expressway close to one another. If you don't pay attention to the signs, you may end up traveling in the wrong direction.


If you're not careful when you enter an expressway, you may even start to drive up an exit ramp!
If you try to enter what you think is an entrance ramp and you see red and white signs marked DO NOT ENTER or WRONG WAY, immediately pull over to the side of the road, turn around, and exit the ramp.


Expressway entrances include three areas: the entrance ramp (1), the acceleration lane (2), and the merge area (3).
As you approach the expressway, evaluate the traffic conditions and look for a gap in traffic. Always yield the right-of-way to vehicles on the expressway.


Entrance Ramps

Entrance ramps (also known as "on-ramps") deliver drivers to the acceleration lane and give them time to scan the road and determine their speed and space needs before entering the flow of traffic. These ramps may be uphill, downhill, or level with the expressway.
As soon as you enter an entrance ramp, begin checking traffic on the expressway. Quickly glance in your side mirror and over your shoulder to find a gap in traffic. As you approach the expressway, be sure your turn signal is activated.


On some entrance ramps, it may be difficult to see what's happening on the expressway because the ramp is curved, the expressway is higher than the ramp, or there is a high wall between the ramp and the expressway.
In these situations, pay attention to the end of the ramp to watch for potential conflicts. Adjust your speed if you see heavy traffic on the ramp or expressway.

To reduce risks on entrance ramps:

Look at the speed limit sign as you enter the ramp and adjust your speed appropriately. Be especially careful on entrance ramps with sharp curves.
Be sure you're in the correct lane to enter the expressway (on some ramps, another lane will lead back to the roadway).
Be ready for slow or stopped traffic on the ramp or expressway. Avoid stopping abruptly or encroaching on traffic ahead of you.



At some entrances, timed entrance lights, or Ramp Meters, are used to control traffic flow by providing a gap between vehicles entering the expressway. Ramp meters usually have only two signals, red and green. Typically, only one car can enter on a green light, although a different limit, such as two cars per green light, may be posted.
When you approach a ramp meter, come to a full stop and wait for the light to turn green. Never try to rush through a ramp meter.


Some expressway entrance ramps have two lanes that merge into one lane at the end of the ramp. The double merge lanes allow vehicles on high volume entrance ramps to create gaps in traffic and merge safely.
On these ramps, there may be separate ramp meters for each lane. Drivers may use any lane available to them and should obey the signal light associated with that lane.


Acceleration Lane

The acceleration lane is the area of an expressway entrance that is used by drivers to speed up before merging with traffic. Pay attention to the speed of traffic on the expressway so you know how fast you should be driving.
On shorter acceleration lanes, you'll need to accelerate more quickly to match the flow of traffic. Search for a gap as you approach and be prepared to adjust your speed.


Sometimes there may not be an acceleration lane between the entrance ramp and the merge area. At other times, the acceleration lane will be clear but the expressway will be so crowded that you'll need to stop and wait before merging.
Don't proceed until you can identify a safe gap to enter. As you enter, accelerate quickly so you can match the speed of traffic.

Merge Area

Immediately following the acceleration lane, the merge area is identified by a broken white line. It is in this area that you are allowed to change lanes to merge with expressway traffic.
You may only attempt to merge over a broken white line. The triangular area between the acceleration lane and the roadway delineated by solid white lines is known as a Gore Area. Never drive in a gore area.

Before you enter an expressway, you must adjust your speed to match the flow of traffic.
Once you're on the expressway, help other drivers merge with traffic by reducing your speed near expressway entrances. When you notice drivers trying to merge, slow down or move into an adjacent lane to give them a safe gap for merging.

To merge with expressway traffic, you must identify a gap large enough for your car to fit into without conflict. In general, there must be a gap of at least four seconds between two cars for you to enter, as this will give you about two seconds in front of and behind your car once you enter the expressway.
Remember that vehicles on the expressway have the right-of-way. Don't try to squeeze into a gap that is too small. Wait at the end of the merge area until there is a sufficient gap.


To reduce risks while merging:

Make sure your signals are activated and continue signaling until you've completely merged with traffic.
Be sure you maintain a safe following distance with vehicles on the entrance and the expressway.
Watch for vehicles changing lanes at merge points.
Anticipate the actions of the driver entering ahead of you, as he or she may suddenly slow or stop.


Once you've started to enter an expressway, do not stop or turn around. Continue until you've merged with expressway traffic. If you stop suddenly while entering an expressway, other drivers may not be prepared to react in time and a collision may result.
Even if you realize you're going the wrong way, you should enter the expressway. Exit at the next opportunity and turn around.


Weave Lanes

On some expressways, a Weave Lane is used by both entering and exiting traffic. In places where a weave lane is used, drivers enter and exit the expressway at the same location.
Because multiple lanes of traffic must interact with each other on weave lanes, the potential for conflict is high. When entering an expressway on a weave lane, yield to drivers using the same weave lane to exit.


Once you're on the expressway, make sure you're driving at a speed that is legal and safe given current visibility and road conditions, and that allows you to keep up with the flow of traffic.
When you go faster or slower than other traffic on the expressway, you increase the risk that you'll be involved in a collision. Maintain a following distance of at least four seconds and try to keep an open area to at least one side so you'll have an escape route in an emergency.


Drive in the lane that allows you to proceed safely and with the fewest conflicts with other drivers. Your lane choice may be affected by the volume and speed of traffic, the types of vehicles on the road, and the location of your intended exit.
If you have to cross several lanes to reach the ideal position, change one lane at a time.

The extreme left lane of an expressway is for faster traffic, and the right lane is for slower traffic:

Use the right lane for driving more slowly or if you're planning to leave the expressway after a short time. Due to their speed limitations, large vehicles are more likely to drive in lanes on the right.
Use the center and left lanes for passing and driving at high speeds. In general, the fastest traffic will be in the leftmost lane of the expressway.


Pay attention to the actions of other drivers around you and move into another lane if you can reduce the risk of a collision by doing so.

If another vehicle is following closely behind you, move to your right, into a slower lane.
If another driver is trying to merge into your lane, move into another lane to give him or her more space, if possible.


Avoid weaving through lanes as it increases the risk of collisions and irritates other drivers on the expressway. In heavy traffic conditions, it can also create further congestion by slowing down other drivers.
When you intend to leave the expressway, begin moving towards the exit lane well in advance. Never attempt to cross several lanes at the last minute. If you wait too long, remain on the expressway and exit at the next opportunity.

After you enter an expressway, move into the most appropriate lane as soon as you can and remain in that lane as long as possible. Due to the volume of other traffic and the speed with which you must make decisions, you'll face increased risk whenever you have to make a maneuver.
The key to driving on the expressway is to keep up with the flow of traffic and maintain a safe space around your car. By doing so, you'll be better prepared to perform any necessary maneuvers.

Because there are no intersections on expressways, most maneuvers you'll perform will involve changing your lane position or moving between lanes. You may need to change lanes when:

Entering or exiting the expressway
Allowing a driver to enter your lane
Following large or slow-moving vehicles
Approaching an obstruction on the road ahead
Passing another vehicle


The risks associated with changing lanes are increased on an expressway because more than one driver may seek to enter the same lane at the same time from different positions.
When preparing to change lanes, check your mirrors and over your shoulders and make sure that the drivers around you aren't about to change lanes. At high speeds, vehicles to your rear can enter your blind spot very suddenly.

Always scan the expressway at least 10 to 15 seconds (about a quarter of a mile) ahead of your position so you can anticipate potential hazards and avoid last minute maneuvers.
Remember the importance of shifting your gaze across several different visual ranges. On expressways, it's especially important to keep your eyes moving so you can spot hazards quickly, as you'll have less time to process and respond to a situation when driving at high speeds.



Keep in mind that when traveling at 60 mph, you'll travel almost 900 ft in the span of ten seconds. To pass another vehicle safely, you'll need twice that—over a third of a mile!
It can be difficult to judge the speed and distance of cars a third of a mile away. In general, if a car is close enough that you can see it approaching, it's probably not safe for you to pass.


Avoid passing on an expressway when:

You're approaching a No Passing zone or a place where the road narrows, including a bridge, tunnel, or underpass
There's a long line of slow-moving or stopped vehicles ahead of you
The vehicle ahead of you has suddenly slowed for an unknown reason
There are obstructions to your line of sight