module 6 2009

Mod 6

Characteristics of Expressways

Entering & Exiting

High Speed Considerations

Controlled access (limited Controlled access (limited entry and exit)entry and exit)

High speed (up to 65 mph)High speed (up to 65 mph)

Divided by a barrier or Divided by a barrier or median median

Multiple lanesMultiple lanes

May have minimum speed May have minimum speed limitlimit

Only for motorized vehiclesOnly for motorized vehicles

Characteristics of an ExpresswayCharacteristics of an Expressway

As speed increases,As speed increases,

Steering input to maneuver the vehicle DECREASES

The faster you travel the less you have to steer

Cloverleaf InterchangeCloverleaf Interchange

A cloverleaf interchangeA cloverleaf interchange has a series of entrance and exit ramps that resemble the outline of a four leaf clover.

allows for the interchange of two expressways or major roadways.

has shared entrance and exit weave lanes.

This designThis design

Traffic is permitted to move ONLY in the direction indicated by the arrows.

Diamond InterchangeDiamond Interchange

A diamond interchangeA diamond interchange is designed to be used when a road with slower speeds crosses a busy expressway.


for the interchange of a major roadway with a secondary dual or multiple lane roadway.

This design allows:This design allows:

Trumpet InterchangeTrumpet Interchange

A trumpet interchangeA trumpet interchange is used when an intersecting side road forms a T intersection with the expressway.


This design:This design:

accommodates the T-intersection flow of traffic at the junction of two roadways.

allows for traffic on a secondary two-way street to merge onto a multiple lane roadway.

Frontage Road InterchangeFrontage Road Interchange

Frontage Road InterchangesFrontage Road Interchanges allow vehicles using parallel secondary two-way or one-way roadways to merge onto a major multiple lane roadway.


drivers to exit a multiple lane roadway and use the parallel frontage road.

secondary road traffic flows to mix efficiently with higher speed traffic flows on the multiple lane roadway.

This design allows:This design allows:

Common Expressway SignsCommon Expressway Signs

Interstate signsInterstate signs

Warning signsWarning signs

Guide signsGuide signs

HOV = HOV = Restricted laneRestricted lane

A major contributor to your decision as to how you will maintain a safe A major contributor to your decision as to how you will maintain a safe path of travel, proper lane position, and your lane choice, is based on path of travel, proper lane position, and your lane choice, is based on the information provided by the road signs and lane markings.the information provided by the road signs and lane markings.

Entrance RampsEntrance Ramps

EntranceRamp

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Entrance ramps provide one-way Entrance ramps provide one-way directional access to an expressway.directional access to an expressway.

The ramp is divided into three sections:The ramp is divided into three sections:1. 1. The Entrance or Access RampThe Entrance or Access Ramp — — gives the

driver time to begin evaluating traffic conditions.

2. 2. The Acceleration LaneThe Acceleration Lane — — allows a driver to adjust vehicle speed to the speed of traffic on the expressway.

3. 3. The Merging AreaThe Merging Area — — allows the driver to merge onto the expressway.

*Search for: entrance # & direction

wrong way or do not enter signs

Use the left-lane signal indicator

Accelerate to the speed of traffic

Monitor gap on expressway

Never STOP!

Acceleration LaneAcceleration Lane

Acceleration LaneAcceleration Lane

Reduced Risk Lane ChangesReduced Risk Lane Changes

Entering or exitingEntering or exiting

Allowing another driver Allowing another driver to enterto enter

Following large or Following large or slow-moving vehiclesslow-moving vehicles

Lane ahead becomes Lane ahead becomes blockedblocked

Being tailgatedBeing tailgated

AnimalsAnimals

PassingPassing

Reasons for changing lanes include:Reasons for changing lanes include:

EntranceEntranceRampRamp

ExitExit

RampRamp

Choosing Lanes at Exit or EntranceChoosing Lanes at Exit or EntranceRight Lane:Right Lane: Heavier and slower vehicles

Vehicles entering the expressway

Vehicles getting ready to exit

Left Lane:Left Lane:Higher speed and passing traffic

Exit / Entry

Right Lane

Center Lane

Left Lane

Center Lane:Center Lane:Long distance or passing

Multiple Lane Roadway ExitMultiple Lane Roadway Exit

An expressway exit has two An expressway exit has two components:components:

1. The Deceleration Lane —1. The Deceleration Lane — gives the driver the time and space needed to adjust his/her vehicle’s speed to the slower posted ramp speed without disrupting the flow of traffic on the expressway.

2. The Exit Ramp —2. The Exit Ramp — allows traffic to enter an adjoining roadway.

ExitRamp

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**Slow down!

Potential Exiting ProblemsPotential Exiting Problems

“Weave” lane conflicts

Short deceleration lane

Sharp curve on ramp

Traffic stopped on the exit ramp

There may be a STOP There may be a STOP sign or a traffic light at sign or a traffic light at the end of the exit ramp. the end of the exit ramp. The driver must adjust The driver must adjust from a fast speed to a from a fast speed to a STOP in a short distance.STOP in a short distance.

Weave LaneWeave Lane Traffic entering and exiting the expressway uses the same lane.Traffic entering and exiting the expressway uses the same lane.

To avoid a conflict, To avoid a conflict, the driver in the the driver in the BLUE car entering from the car entering from the entrance ramp must yield the right-of-way to the driver in the entrance ramp must yield the right-of-way to the driver in the RED car who is leaving the expressway (entering yields to exiting). who is leaving the expressway (entering yields to exiting).

Weave Lane

R.O.W. = RED car is already on the road!

High Speed ConsiderationsHigh Speed Considerations

1. If you miss your exit on the interstate, you must exit & re-enter going the correct direction.

2. If you miss your exit, you should continue the next one.

3.Where are U-turns allowed on expressways? NO WHERE

4. Pack driving is when vehicles get “bunched up.”

-- Dangerous because driver’s have no space cushion. No time to avoid crash

5. No space & no escape routes cause chain reaction collisions.

Highway HypnosisHighway Hypnosis

Plan breaks and rest stops to combat highway hypnosis or go to a safe area for rest or sleep when tired.

Is a dulled or drowsy condition that can occur when driving long distances

Situation becomes worse when the driver’s eyes focus on the center line.

Ramp MeteringRamp Metering

Used to control large volumes of traffic entering Used to control large volumes of traffic entering expresswaysexpressways

Uses a system of lights and sensorsUses a system of lights and sensors

Allows only a few cars at a time to enter congested Allows only a few cars at a time to enter congested limited access highwayslimited access highways

How does Urban differ from Rural?How does Urban differ from Rural?

A lot more traffic in urban areas.A lot more traffic in urban areas.

Slower speeds, too.Slower speeds, too.

Special Roadway ConditionsSpecial Roadway Conditions

Disabled vehiclesDisabled vehicles

Expressways through citiesExpressways through cities

• Don’t be a “rubber necker”

• Give the disabled vehicle plenty of room

• Pull as far off the roadway as possible if your vehicle becomes disabled

• Avoid driving in the right lane when vehicles are merging

• Search for signs, signals, and roadway markings

• Search for exits early and adjust position in adequate time to exit safely

• Don’t make last minute lane changes to gain access to an exit

• Monitor the zones around your vehicle and adjust position to create space cushions

Short Trips on ExpresswaysShort Trips on Expressways

Know the name, route, and number of the entrance and exit to be used

In VA mile markers = Exit numbers

Take a local map

Plan a time to travel to avoid Plan a time to travel to avoid congestion around major citiescongestion around major cities

Identify theIdentify the Exit Exit EarlyEarly

Exits are marked with guide signs, usually one to two miles before the exit.

You can determine if an exit is a right exit or a left exit by the position of the exit number on the sign. So, Exit 45A is a right exit, because in this picture the exit number on the upper right-hand side of the sign.

In Virginia, exit numbers correspond with mile marker numbers.

About one-half mile (20- to 30- seconds) before the exit, signal and move to the lane closest to the deceleration lane.

Multiple Lane Roadway DangersMultiple Lane Roadway Dangers

Vehicles moving onto the shoulder Vehicles moving onto the shoulder or re-entering the roadwayor re-entering the roadway

Tires losing traction and hydroplaning Tires losing traction and hydroplaning during wet weather conditionsduring wet weather conditions

Slow moving vehicles ahead or “Pack Slow moving vehicles ahead or “Pack Driving”Driving”

Two vehicles changing lanes at the Two vehicles changing lanes at the same time into same lanesame time into same lane

Windy and/or wet sections of the roadwayWindy and/or wet sections of the roadway