Long Red, Short Green, I Got Skipped, and Why Do I Always Have To Stop Who Runs These Signals and How Do I Get Ahold Of Them?

Transcription

1 Long Red, Short Green, I Got Skipped, and Why Do I Always Have To Stop Who Runs These Signals and How Do I Get Ahold Of Them? A Primer on Traffic Signal Operations In Sacramento County August 21, 2014

2 What Makes up a Traffic Signal? Start with an intersection that has a lot of cars and/or a lot of collisions Put up traffic control devices Poles with signal heads/indications (vehicle, pedestrian, bicycle, transit) Signs and markings to designate what you can do where Sensors to detect vehicles, bicycles, pedestrian, and emergency vehicles

3 What Makes up a Traffic Signal? Start with an intersection that has a lot of cars and/or a lot of collisions Put up traffic control devices Poles with signal heads/indications (vehicle, pedestrian, bicycle, transit) Signs and markings to designate what you can do where Sensors to detect vehicles, bicycles, pedestrian, and emergency vehicles

4 What Makes up a Traffic Signal? Start with an intersection that has a lot of cars and/or a lot of collisions Put up traffic control devices Poles with signal heads/indications (vehicle, pedestrian, bicycle, transit) Signs and markings to designate what you can do where Sensors to detect vehicles, bicycles, pedestrian, and emergency vehicles

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7 What Makes up a Traffic Signal? Start with an intersection that has a lot of cars and/or a lot of collisions Put up traffic control devices Poles with signal heads/indications (vehicle, pedestrian, bicycle, transit) Signs and markings to designate what you can do where Sensors to detect vehicles, bicycles, pedestrian, and emergency vehicles

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9 What Makes up a Traffic Signal? continued Sensors to detect vehicles, bicycles, pedestrian, and emergency vehicles Inductive loops in the pavement Video Microwave/Radar Thermal Push buttons Infrared/Optical GPS Why? So the signal can respond to only vehicles, bikes, and peds when they actually are there and need service: Traffic Responsive Operation

10 What Makes up a Traffic Signal? continued Install a controller (computer) in a cabinet at the intersection The controller takes information from the sensors: inputs And tells the indications what they should be displaying: outputs There is additional equipment in the cabinet Used to be LOTS of wires. Not so much anymore Sensor/detector processing cards that interface between the information coming from the street and the controller Drivers to power the indications the controller says to turn on Conflict Monitor (MMU) to make sure conflicting greens don t come on

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12 What Makes up a Traffic Signal? continued Install a controller (computer) in a cabinet at the intersection The controller takes information from the sensors: inputs And tells the indications what they should be displaying: outputs There is additional equipment in the cabinet Used to be LOTS of wires. Not so much anymore Sensor/detector processing cards that interface between the information coming from the street and the controller Drivers to power the indications the controller says to turn on Conflict Monitor (MMU) to make sure conflicting greens don t come on

13 Lot a Wires Not so Much

14 So why doesn t it serve me right away and stay green as long as I need? (long red, short green) Usually it s the detection in the field or sometimes the equipment in the cabinet If the sensor(s) for the side street or left turn pockets, or the pedestrian push buttons for crossing in front of you are stuck/locked, the controller thinks there are vehicles or peds there and stays green up to it s maximum programmed green time. (Could be seconds) The controller has been programmed to go back serve a direction every cycle: recalled

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16 So why doesn t it serve me right away and stay green as long as I need? (long red, short green) continued If the a couple of loops are bad, a vehicle could be missed and have to wait until another vehicle comes up and puts in a call for service. This could make for a long wait, or if enough sensors are bad, skip that direction all the time. Other things that can happen On rare occasions, an emergency vehicle in an opposite direction will pre-empt the signal and hold it there until they ve passed through. This can result in a long red or a skip The intersection is being coordinated with the nearby signals by a master controller

17 So why doesn t it serve me right away and stay green as long as I need? (long red, short green) continued Somebody was texting and forgot to pay attention to the signal until all their (and your) time was gone The intersection is being coordinated with the nearby signals by a master controller That changes the order left turns are served during coordination from the order they re served when running independently (lead-lag operation versus lead-lead) That can change how long the maximum green is by time of day Bad coordination can cause frequent stops

18 Speaking of signal coordination, this is why I REALLY like my job.

19 I get to sit in a high tech TOC, watching traffic and affecting peoples commutes (lives) from miles away.

20 The central system or advanced transportation system (ATMS) provides access to the master controller, surveillance video and the intersection signal timing.

21 The central system or advanced transportation system (ATMS) has tools for analyzing how much green time different directions have been using at intersections in order to optimize how much time to program for them under coordination and a graphic to calculate when to turn the main street green going down the road and what s the best order to serve the left turns.

22 From the comfort of the TOC we can make changes to an intersections timing and observe the results in real-time.

23 So what do I do if it doesn t seem to be operating the way it s supposed to? Call 311 This is our new one-stop shop for customer service County-wide including traffic signals Call BUG-DOUG My staff s idea Call Doug s direct line, or maasd@saccounty.net