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Unformatted text preview: Chapter 20 Chapter 20 Basic Principles of Intersection Signalization Basic Definitions 1. Cycle 2. Cycle Length ( C ) 3. Interval Green Interval Change Interval Clearance Interval Red Interval 4. Phase Types of Signal Control 1. Pretimed Operation 2. SemiActuated Operation 3. FullActuated Operation Types of Signal Coordination Master Controllers ComputerControlled Systems Adaptive Traffic Control Systems: SCOOT (Split Cycle Offset Optimization Technique) SCATS (Sydney Coordinated Adaptive Traffic System) RHODES (RealTime Hierarchical Optimized Distributed Effective System) Application of Types of Signal Control: Type of Fixed Applicable Principal Operation Cycle? Conditions Benefits Pretimed YES Detection Temporary Isolated not available installation Pretimed YES Consistent Predictable operations; Coordinated demand; Lowest costs of Closely operation and spaced maintenance. intersections. Application of Types of Signal Control: Type of Fixed Applicable Principal Operation Cycle? Conditions Benefits SemiActuated NO Light xstreet Lowcost for Isolated traffic. flexibility Full Actuated NO Isolated Responsive to wide Isolated location. variation in demand. Coordinated YES Arterial with Lower arterial varying side delay; lower system street demands. delay potential. Permitted Left Turns Protected Left Turns Compound Left Turns Protected Plus Permitted Permitted Plus Protected LeftTurn Options Four Basic Mechanisms: Four Basic Mechanisms: DISCHARGE FROM A STANDING QUEUE DISCHARGE FROM A STANDING QUEUE StartUp Lost Time: StartUp Lost Time: Clearance Lost Time: Clearance Lost Time: Total Lost Time Per Phase: Total Lost Time Per Phase: Basic Concepts Basic Concepts Saturation Headway: Saturation Headway: Saturation Flow Rate: Saturation Flow Rate: ) / ( ) / ( ) / ( ln) / / ( 600 , 3 ) / ( 2 1 2 1 phase s t phase s phase s e hg veh h s veh s h L i + = = = ā Basic Relationships Time Required to Move āNā Vehicles Through a Single Green Phase (T): Effective Green Time for Phase i (g i ): Capacity of an Intersection Lane: h N T + = 1 = C g s c i i i e G g e Y ar y Y t t Y G g i i i i i i L L i i i + = = + = + = + = 1 2 2 1 Sample Problem C = 90 seconds G = 40 seconds Y = 4 seconds l 1 = 2 seconds/phase e = 2 seconds/phase h = 2.2 seconds/vehicle Find: Capacity of Movement Per Lane NOTE: l 2 =Ye=42=2 secs Cycles Per Hour : h cycles N c / 40 90 600 , 3 = = Time Available for Use at Saturation Headway : Seconds in Hour: 3,600 Deduction for Red Time: (90404) 40 = 1,840 Deduction for Lost Times: (2+2)40 = 160 Time Available (secs) = 1,600 Capacity Per Lane : h veh c / 727 2 . 2 1600 = = Alternative Approach : Find the Saturation Flow Rate: Find the Capacity of a Lane: Find the Effective Green Time: ln / / 636 , 1 2 . 2 3600 hg veh s = = s e G g . 40 . 2 . 2 . 40 1 = + = + = h veh C g s c / 727 90 40 636 , 1 = = = Four Basic Mechanisms:...
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 Spring '10
 Lee
 Delay, saturation flow rate, overflow delay, average overflow delay

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