Intersections & Turnabouts
Intersections Come in a Variety of Designs � + 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 o 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 What clues • Power lines 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: 12-15 sec. ahead • Look for an open POT • Search left, front, right zones – pause during search o Search 12-15 4-6 sec. ahead seconds ahead o Search 4-6 seconds o Search 90 degrees to the left and right
R IGHT OF WAY � Right of Way Must be Given , Not Taken � Failure to yield right of way causes collisions every day! � Who must yield when: • One vehicle arrives first? • Two vehicles arrive at the same time?
CONTROLLED INTERSECTIONS � Signs and Signals at Controlled Intersections �
SIGNAL LIGHTS � How should a driver treat What is the “ point of no return ” a “ fresh ” green light and a when approaching a yellow light? “ stale ” green 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 The light flashes to warn the light is preparing to turn red Don ’ t walk signals burn steadily when crossing is not permitted
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 Sensors imbedded traffic movements 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 one block prior to turning • Signal at least 100 feet, preferably 5 seconds before the turn Is this driver • Check rear zone before slowing 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 Protected turn lanes are less risky Yield at unprotected left turns
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 3 ½ 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? At least 100 feet, or 5 seconds What lane position should a driver enter before turning left? Lane Position 2 Before braking, what should a driver do? Check rear zone When should the tires be turned for a turn? When beginning the turn
LEFT TURNS AT INTERSECTIONS � Ask yourself these questions at intersections: • How fast is traffic moving? • Will on-coming traffic continue into the intersection or will they turn? • Is the gap sufficient? • Any LOS-POT Restrictions? • Is there an open zone available to enter? • Is there time to clear the intersection?
LEFT TURNS AT INTERSECTIONS � Searching Intersections Prior to turning, in what direction is the last area to search? • To the left • To the front • To the right • To the target area If the light is green and the intersection is blocked, what should the driver do?
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 Photo courtesy of the Insurance Institute for Highway Safety • Search for pedestrians and bicyclists
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 • Is traffic approaching? Where? and right • 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 U-Turns can be protected or unprotected 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
CROSSING RAIL GRADE INTERSECTIONS � Every year about 4,000 collisions occur 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 Pavement Markings Yellow Diamond RR Warning Sign Shape Sign Stop Line
RAIL GRADE ACTIVE SIGNALS � Electric signs warn drivers Of an approaching train Flashing Red lights, with or without bells 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?
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