Chapter 7 _3_

Chapter 7 _3_ - Signalized Intersections: Timing...

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Unformatted text preview: Signalized Intersections: Timing & Analysis square6 Signalized intersections serve as the major routing nodes of a roadway network. square6 Optimized signal timing improves the efficiency of intersection traffic operations. 2 Popular Traffic Detectors square4 Acoustic square4 GPS (tracking) square4 Infrared Sensors square4 Inductance Loop Detector (ILD) square4 Video Imaging Processing (VIP) square4 3 Freeway Monitoring Popular Traffic Detectors 4 Actuated Signal Control Popular Traffic Detectors 5 Ramp Meter Control Popular Traffic Detectors 6 Structure of Traffic Detection Systems Detector Processor/Controller Storage Video Image Processors Scene Camera Image Segmentor Parameter Estimator Traffic Controller Video Image Processors 9 Signal Control Modes square6 Pre-timed or fixed-time square6 Cycle length, phase sequences, green times, etc are all pre-determined and fixed for a period of time square6 Generally needs no sensors square6 Mostly found on downtown streets, or streets with fixed traffic demand patterns. 10 square6 Semi-actuated square6 Sensors are installed on minor street to detect vehicle presence. Green rest on main street until a vehicle call from minor street. square6 Responsive to traffic demand changes square6 Usually found on major/minor street intersections square6 Cycle length and phase sequences are variable Signal Control Modes 11 square6 Fully-actuated square6 Sensors are installed on all approaches square6 Responsive to changes in traffic demand square6 Cycle length and phase sequences are variable Signal Control Modes 12 Initial and Extension Green Time square6 Typical minimum initial green times are on the order of 10 seconds square6 If vehicle is arriving, 2 to 4 seconds for extension 13 Max-out and Gap-out Conditions square6 If the phase terminates at the maximum green time, it is referred to as a max-out condition . square6 If the phase terminates prior to reaching the maximum green time, due to the time gap in successive vehicle arrivals exceeding the extension interval, this is referred to as a gap-out condition . 14 Procedure for Designing and Analyzing Pre-timed Signals square4 Select signal phasing plan square4 Determine demand/capacity levels square4 Establish analysis lane groups (unit of analysis) square4 Adjustments to demand and saturation flow rates (PHF, etc) square4 Compute critical lane or lane groups flow ratio (or v/s ratio) and total lost time square4 Determine signal timing plan square4 Compute cycle length square4 Allocate green times square4 Compute clearance and change intervals square4 Check pedestrian crossing time square4 Compute LOS (based on delays) 15 I. Select Signal Phasing Odd numbers to indicate left turns, goes clockwise starting from the NB....
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This note was uploaded on 03/10/2012 for the course ECI 161 taught by Professor Tafazzoli during the Winter '12 term at UC Davis.

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Chapter 7 _3_ - Signalized Intersections: Timing...

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