Intersections & Turnabouts Intersections Come in a Variety of - - PowerPoint PPT Presentation

Intersections & Turnabouts

Intersections Come in a Variety of Designs

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A crossroad - Two or more roads intersect

T A Tee - One road ends where the other road crosses.

At a Tee intersection, vehicles on the through road have the right of way. Stop and yield the right-of-way to the vehicles on the through street.

Y One road becomes two, or two roads become one

• A traffic circle is where several roads meet in a circle

Traffic moves around the circle and exits at the desired new road

Search for Intersection Clues

Search at least 20-30 seconds ahead for intersection clues:

• Street signs and lights
• Roadway markings
• Stop signs
• Signal lights
• Crossing traffic
• Parked vehicles on cross streets
• Turning traffic
• Traffic preparing to stop or stopped
• Changes in road surface
• Power lines

What clues identify the next intersection?

Search for Directional Types

Intersections can change the way traffic flows. Examples of different traffic flows include:

• Two-way
• One way to one way
• One way to two way
• One way to multi-lane
• Two way to one way
• Lane reduction/merging

APPROACHING INTERSECTIONS

When approaching:

• Look for an open POT
• Search left, front, right

zones – pause during search

12-15 sec. ahead 4-6 sec. ahead

• Search 12-15

seconds ahead

• Search 4-6

seconds

• Search 90 degrees

to the left and right

RIGHT OF WAY

Who must yield when:

• One vehicle arrives first?
• Two vehicles arrive at the same time?

Right of Way Must be Given, Not Taken

Failure to yield right of way causes collisions every day!

CONTROLLED INTERSECTIONS

Signs and Signals at Controlled Intersections

SIGNAL LIGHTS

How should a driver treat a “fresh” green light and a “stale” green light? What is the “point of no return” when approaching a yellow light?

TURNING RIGHT ON RED

Permitted in all states and the District of Columbia, except where prohibited

Did the driver in the white SUV yield the right of way?

LEFT ON RED

Can a driver approaching this Boise intersection make a left turn on a red light?

PEDESTRIAN CROSSING LIGHTS

Crossing signs burn steadily when a pedestrian may cross

Don’t walk signals burn steadily when crossing is not permitted The light flashes to warn the light is preparing to turn red

PEDESTRIAN CROSSINGS

At some crossings, pedestrians carry highly visible flags while in the crosswalk At others, a clock counts down seconds letting pedestrians know available time to cross

PEDESTRIAN CROSSINGS

Watch for pedestrians crossing in the middle of a block. They have the right of way!

COMPUTERIZED SIGNAL SENSORS

• Traffic signals are actuated

from 6' x 6' wire loops embedded in the pavement

• Also known as traffic detection

loops

• The loops detect vehicles as

they approach the traffic signal and send information to a control cabinet located on a corner near the intersection

• The traffic control cabinet then

assigns most of the available green time to the heaviest traffic movements

Sensors imbedded in the pavement

“Dog House” Signals

• The Doghouse” signal is a new type of left turn

signal to improve traffic flow at major intersections

• A five light display incorporates both a green and

yellow left turn arrow

• The green arrow (indicating a protected turn)

will turn yellow while the solid green light remains.

• When the green

arrow goes off, an unprotected left turn is still allowed until the light turns RED

STAGGERED STOPS

A staggered stop gives more room for cars turning left in front of you as shown in the picture below

RIGHT TURNS AT INTERSECTIONS

• Usually requires more time

than turning left

• Usually requires merging

with other traffic

• Enter correct lane position
• ne block prior to turning
• Signal at least 100 feet,

preferably 5 seconds before the turn

• Check rear zone before slowing

Is this driver making a legal right turn?

RIGHT TURNS AT INTERSECTIONS

Time and Gap Needs for a Right Turn

• Merging with traffic

moving at 30 mph requires at least 6-7 seconds (one block gap)

• Merging with traffic

moving at 55 mph requires at least a 3 block gap

Did the driver in the white truck have a safe gap for a right turn?

RIGHT TURNS AT INTERSECTIONS Search Intersections for:

• Vehicles approaching

the intersection

• Pedestrians
• Bicyclists
• LOS-POT

Restrictions

RIGHT TURNS AT INTERSECTIONS Searching Intersections

If there is a LOS or POT restriction – REDUCE SPEED Final search is in the direction of the turn Confirm an open zone exists Exit and enter corresponding lanes Be alert to drivers drifting in their lane Cancel signal Describe the conditions at this intersection

RIGHT TURN LANE MERGE AREAS Turn lanes help move traffic

• Signal right
• Search for stopped

traffic in the merge lane

• Will the light stay

green long enough to provide sufficient time for the merge?

LEFT TURNS AT INTERSECTIONS

More risky because:

• Crossing multiple lanes
• Vehicle in intersection

longer Yield at unprotected left turns Protected turn lanes are less risky

LEFT TURNS AT INTERSECTIONS

Time and Gap Needed for a Left Turn

• Merging with traffic moving

at 30 mph requires at least 7-8 seconds (more than one block gap)

• Merging with traffic moving

at 55 mph requires at least a 3½ block gap

These vehicles are approaching at 30 mph. Is the gap large enough to make a left turn here?

LEFT TURNS AT INTERSECTIONS Good Habits

When should a driver signal before turning left? What lane position should a driver enter before turning left? Before braking, what should a driver do? At least 100 feet, or 5 seconds Lane Position 2 Check rear zone When should the tires be turned for a turn? When beginning the turn

LEFT TURNS AT INTERSECTIONS

• Is there time to clear the

intersection?

• Is there an open zone

available to enter?

• How fast is traffic moving?
• Any LOS-POT Restrictions?
• Will on-coming traffic continue into the

intersection or will they turn?

• Is the gap sufficient?

Ask yourself these questions at intersections:

LEFT TURNS AT INTERSECTIONS Searching Intersections

Prior to turning, in what direction is the last area to search? If the light is green and the intersection is blocked, what should the driver do?

• To the left
• To the front
• To the right
• To the target area

When the light turns green, what should this driver do?

DRIVING IN TRAFFIC CIRCLES Traffic circles are circular intersections controlled by yield signs

• They increase traffic flow and studies have shown they

have less crashes, injuries, and fatalities

Photo courtesy of the Insurance Institute for Highway Safety

Most Idaho cities now have several of these!

DRIVING IN TRAFFIC CIRCLES Good Habits

• See the Yield sign on approach
• Slow, search for pedestrians,

bicyclists

• Stop only if necessary
• Yield to traffic in the circle
• Select a safe gap when entering the

circle

• When traveling in the circle, Yield to

traffic attempting to leave

• Signal for your exit
• Search for pedestrians and bicyclists

Photo courtesy of the Insurance Institute for Highway Safety

UNCONTROLLED INTERSECTIONS

Typically located in neighborhoods and areas of light traffic Why are uncontrolled intersections dangerous?

UNCONTROLLED INTERSECTIONS Look for clues, an oncoming driver may intend to turn left:

• Head is moving; driver is

looking to the left

• Vehicle is slowing
• Wheels are turning left

TURNING AT UNCONTROLLED INTERSECTIONS

• Search 4-6

seconds ahead – and 45 degrees left and right.

• Then search

12-15 seconds ahead and 45 degrees left and right

• Is traffic approaching?

Where?

• Are there LOS-POT

restrictions?

• What is your best lane position?
• When should you signal?

U-TURNS AT INTERSECTIONS Know if a U-Turn is permissible

When making a legal U-Turn, use these good habits:

• Look for a 20-30 second gap in traffic
• Be able to see 500 feet in all directions
• Start the U-Turn from the left most lane
• Check rear, tap brake lights
• Signal left, move to LP2
• Turn head, look to target area at the end of the U-Turn
• Turn sharply left, moving slowly, eyes on target area
• Do not stop if there is sufficient space for a complete U-Turn

U-Turns can be protected or unprotected

CROSSING RAIL GRADE INTERSECTIONS

Every year about 4,000 collisions

• ccur at highway-rail grade

crossing in the United States

• About 500 deaths
• 1,500 serious injuries

RAIL GRADE PASSIVE SIGNALS

Non-electric signs that warn drivers the road ahead crosses a railroad track

RR Warning Sign Yellow Diamond Shape Sign Pavement Markings Stop Line

RAIL GRADE ACTIVE SIGNALS

Flashing Red lights, with or without bells

Electric signs warn drivers Of an approaching train

Flashing Red lights, with bells and gates close the road when a train approaches

Identify the active and passive signals at this crossing

The school bus lights are flashing. Why?

TRAIN FACTS

• What takes a mile to stop when traveling 55 mph?

A fully loaded train with 100 cars, weighing about 12 million to 20 million pounds needs 18 football fields to stop

• The weight ratio of a 3,000 pound car to a can of pop is 4,000 to 1
• The weight ratio of a 12 million pound train to a 3,000 car is 4,000 to 1
• A train is 17 feet high and 10 feet wide
• A train is three feet wider than both sides of the track

• Every day in the United States, a vehicle or

pedestrian is struck by a train every two hours

• Almost 50 percent of all collisions at public grade

crossings occur where active signals exist (gates, bells, lights)

• Most crashes occur within 25 miles of home

TRAIN FACTS

SAFE BEHAVIORS AROUND RR CROSSINGS

• ALWAYS EXPECT A TRAIN. Scheduled passenger trains can

run early or late, and freight trains do not follow set schedules

• Do not walk, run, ride bicycles or motorcycles, or operate all-

terrain vehicles on railroad right-of-way, or through tunnels

• Cross tracks only at designated pedestrian or roadway

crossing—observe and obey all warning signs and signals

• Do not hunt, fish or bungee jump from railroad trestles
• Do not attempt to hop aboard railroad equipment at any time

—a slip of the foot could cost you a limb, or your life

SAFE BEHAVIORS AROUND RR CROSSINGS

• Never drive around lowered gates—it’s illegal and deadly. If you

suspect a signal is malfunctioning, call the 1-800 number posted on

• r near the crossing signal or your local law enforcement agency
• Never race a train to the crossing—even if you tie, you lose
• Do not get trapped on the tracks. Only proceed through a highway-

rail grade crossing if you are sure you can completely clear the crossing without stopping

• If your vehicle stalls on a crossing, immediately get everyone out and

far away from the tracks. Move away from the tracks in the direction from which the train is approaching—debris will move away from you, not toward you

• Call your local law enforcement agency for assistance

• At a multiple track crossing while waiting for a train to pass,

search for a second train on the other tracks, approaching from either direction

• Do not shift gears on railroad tracks; your vehicle may stall
• STOP

If there is a stop sign If the gates are going down If the lights are flashing and bells are sounding If a train is approaching

• Turn off the radio when approaching a

crossing—LISTEN for a train!

SAFE BEHAVIORS AROUND RR CROSSINGS

The Good, the Bad, and the Ugly

Intersections are a necessary part

• f our highway

transportation system – but they are also where most conflicts and collisions occur. Knowing the laws and driving defensively will help you navigate these crossroads.

TURNABOUTS

TURNABOUT OPTIONS

• Consider the Options

Ask yourself: Is it needed? Legal? Safe?

What are the turnabout choices?

• Go around the block
• Use a parking lot
• U-Turn
• Two-Point Turn
• Three-Point Turn

TURNABOUT RESTRICTIONS

• Drivers may not turn the vehicle around

unless it can be done safely and without interfering with other traffic Turnabouts are restricted when

• in a curve
• approaching or near a hill where you can’t

see 500 feet in either direction

• in a no passing zone

Mid Block U-Turn

• Ask these questions:

How wide is the street? How much traffic is there? What is the turning radius

• f your vehicle?

Is it legal? Is this a safe location and time for a U-Turn?

Mid Block U-Turn

• If no traffic is behind

you or coming in the

• pposite lane, signal,

check all mirrors, and slowly turn around and continue in the

• pposite direction.

Two-Point Turnabout – Backing to the Right

• Use this maneuver in a low-volume area

with no legal restrictions for using a driveway or street

Advantage: drivers are able to re- enter traffic by driving forward This is the safest maneuver from the right side of the road

Two-Point Turnabout – Backing to the Right

• 1

2

Two-Point Turnabout to the Left

• 1

2 1 3 4

Three-Point Turnabout

• The most hazardous turnabout

Consider if:

• a driveway/street is not available
• driving around the block is not

an option

• available space is insufficient for

another type of turnabout

Three-Point Turnabout

• 2

1 3 4

Be Safe!