unit 14

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.

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.

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.

Pay attention to all signs, signals, and road markings: In addition to route and exit signs, you should also watch for indications that traffic lanes are merging, the speed limit is changing, or that a lane is reserved for certain drivers. Signal your intentions: Be sure to flash the appropriate turn signal when changing lanes. Flash your brake lights when you notice traffic slowing ahead.

Adjust your speed to weather conditions: Driving at high speeds when visibility or road traction is reduced by rain, snow, or fog is especially dangerous. Remember that posted speed limits are based on ideal conditions. Avoid driving too slowly: If you are driving slowly relative to other vehicles, you should drive in the right lane so you don't impede other drivers. Maintain a safe gap: A five-second gap is preferable on expressways. Increase the gap in front of your car if you are being tailgated and are unable to change lanes. Don't count on other drivers to do the right thing: Defensive driving requires that you anticipate and avoid potential problems yourself.

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As you review the information presented in this unit, consider how to incorporate the following topics into your driving plan. To reduce risk on the road, you must: Interact with multiple streams of traffic moving in different directions on multi-lane roadways and at intersections Understand the particular advantages and disadvantages associated with driving on expressways Execute the proper procedure for entering and exiting an expressway safely Choose the ideal lane for expressway driving given your speed and destination and the condition of the driving environment Watch for situations on the expressway, such as HOV lanes, toll booths, or disabled vehicles, that will require you to make driving adjustments

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

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.

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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

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.

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.

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.

HOV Lanes When driving on an expressway, be prepared to encounter special lanes designated for the exclusive use of carpools and buses. These are known as High Occupancy Vehicle (HOV) Lanes. HOV lanes are designed to reduce traffic congestion on expressways. They will generally be indicated with road signs and diamond pavement markings.

To drive in a HOV lane, you must have the required minimum number of occupants in your car. This requirement (usually two or three people, including the driver) will be indicated on signs posted along the expressway. These signs may also indicate the hours of the day that the HOV requirements apply. Some HOV lanes can only be entered and exited at locations designated by a broken white line. When double white lines separate an HOV lane from other lanes, it may not be entered or exited.

turnin left

Turning left can be especially difficult at multi-lane intersections because the driver will need to travel through several lanes of cross traffic to complete the turn. On some roads, a short lane reserved for traffic turning left will appear shortly before you reach the intersection. Designed to facilitate traffic flow, these lanes are known as left turn bays.

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.

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.

Signs warning you that your exit is approaching may provide information including the exit's number and name, the distance to the exit, the number of exit lanes available, and whether the exit is on the left or right of the roadway. Watch for yellow panels with the message EXIT ONLY on guide signs posted above the expressway. Lanes beneath these panels will end at the off-ramp and cannot be used by through traffic. If you're not planning to exit the expressway, make sure you're not driving in an EXIT ONLY lane.

deceleration lane and an exit ramp. Use the deceleration lane to reduce your speed to merge with slower traffic on the roadway. An EXIT ONLY lane becomes a deceleration lane when it splits from the expressway. The exit ramp connects the deceleration lane to the roadway. It may be curved, uphill, or downhill.

Before driving on an expressway, be sure your car is in good working order and that you have everything you may need: Check your fuel level as well as your car's tires, lights, and fuel levels. Make sure you have an emergency kit, a spare tire and tools for changing it, battery jumper cables, water, and snacks, as well as any weather-appropriate equipment. If travelling with luggage, be sure to distribute the weight evenly, especially if you'll be driving up or downhill.

When driving on an expressway, always keep the following considerations in mind: Be alert: Keep your eyes moving between several visual ranges and use your rearview and side mirrors constantly to check the traffic behind you. Stay out of others' blind spots: Because drivers change lanes so often on expressways, it's especially dangerous to travel in a position where another driver can't see you. Always allow plenty of room when passing

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.

@ least 4 seconds

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.

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

Even the best drivers can experience an equipment failure or other emergency while driving. If you have to make an emergency stop on the expressway: Warn drivers behind you by tapping the brake pedal. Turn on your hazard lights as soon as possible. Look in your rearview mirror before applying the brakes. Move to the shoulder of the road as quickly and safely as possible. Avoid the shoulder by the center divider, if possible. Once you're on the shoulder, come to a full stop. Remember that it is extremely dangerous to stop or back up on the expressway itself.

If you must stop on the shoulder of the road, you should set up flares or reflectors around your car to warn other drivers. In general, you shouldn't attempt to repair your car on the side of the road. Have it towed for repairs. If the problem is not severe and you can return to the road, exit the shoulder with the same technique you would use to enter from an on-ramp: signal, accelerate as much as possible on the shoulder, and yield to traffic until there is an adequate gap for you to enter.

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.

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.

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 travelling 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

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.

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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.

When preparing to turn right or left at an intersection, remember that you must:

Scan the intersection and the area of the roadway you intend to enter for pedestrians, bicycles, and other vehicles. Move to the proper position for making a turn and activate your turn signal at least 100 ft before you reach the intersection. Proceed cautiously if your view is blocked.

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.

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 travelled and identify when you're nearing your destination.

The monotony of driving on an expressway can often lead to velocitation and highway hypnosis. To avoid velocitation, check your speedometer regularly. Remember to reduce your speed when exiting the expressway. To avoid becoming drowsy or dazed by highway hypnosis, be sure you keep your eyes moving, actively pay attention, and take frequent breaks from driving.

Watch for the following situations and adjust your speed appropriately: Upcoming toll booths, immigration check points, or traffic breaks Disabled vehicles on the road Traffic congestion, especially near urban areas Construction zones and road workers Approaching emergency vehicles

toll booths

Toll Booths On some roads and bridges, you'll need to pay a toll to proceed. Often, drivers face increased dangers at toll booths because of the high volume of vehicles at the toll gate. Moreover, you may encounter distracted drivers trying to get across the roadway at the last minute, as tollbooth lanes are typically designated for specific road users, such as carpools, buses, and trucks. As you approach a tollbooth, make sure you're driving in an appropriate lane.

As you travel across an expressway, look out for tollbooth signs and reduce your speed early as you advance. Watch for traffic backed up at the booth so you can judge whether and when you will need to stop. An open toll booth will be identified by a green light or sign posted above the lane. Once you've passed through the tollbooth, search to your sides for a safe place to merge. Accelerate smoothly to rejoin the flow of traffic.

Exiting an expressway, like entering one, poses additional risks to drivers because it requires driving through multiple lanes of high-speed traffic and making speed adjustments rapidly. The need to exit an expressway should never come as a surprise. Even if you're driving on an unfamiliar road, guide signs posted around the expressway should provide plenty of warning before you arrive at your destination

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.