Question

Describe with sketches the procedure to troubleshoot the traffic light controller.

Answer 1

Considerations of Traffic Signal 

1) Traffic light may have sensors integrated to provide real time traffic information 

2) Based on the traffic information provided by the sensor, the duration of the green/Red LED light for each direction may vary so that the traffic for both the directions are roughly balanced. Time left for the green light should be displayed 

3) When the traffic light for one signal is green, then the traffic for the other directions should be red (with duration displayed in red) 

4) The red light will be switched to yellow when the timer value is 5 sec before switching to red.

5) Violations happen when user expectancy is not met. A user like pedestrian does not expect to stand for more than a minute or two at a signal, when this user expectancy is not met, the pedestrian tries to venture out and violate the signal 

6) The smooth movement of conflicting vehicles is determined by the availability of gaps in traffic. This is true for both pedestrians and vehicular traffic. Understanding of gaps is important for justifying the type of traffic control device, including a traffic signal.

Points to consider for determining signal timings 

1) The signal operational parameters are reviewed and updated (if needed) on a regular basis to maximize the ability of the traffic control signal to satisfy current traffic demands 

2) Geometry of the intersection is the next step in the signal timing process. Determining the lane use (which traffic mode), dedicated vs. shared lane, type of roads interacting (arterial with arterial etc.), type of road infrastructure (ramps, one way streets, etc.) will impact the timing. 

3) Basic signal timing parameters comes next. Pedestrian walk times, flashing don’t walk, yellow time, all red clearance interval, detector gap times all need to calculated or established. 

4) Identify bottlenecks, review conditions, conduct warrant analysis and use engineering judgment in determining traffic signal installation 

5) Determine AM and PM peak hour traffic volumes. 

6) Condition diagram which includes roadway geometrics, parking, driveways, sidewalks, signing, pavement markings, development of intersection quadrants, and any other features pertinent to the study peak hour delay study 

7) A conflict analysis 

8) Capacity analysis of the intersection for current and future years using growth