Traffic Signal Clearance chart 1

[kaparous]

I am a junior traffic Engineer, and I have being struggling to understand the arrangement of the traffic signal clearance chart. Can anyone help?
Thanks in advance

 

[teeman]

I'm not clear as to what you are referring to as a "signal clearance chart". Traffic signal clearance intervals are calulated based on the speed of approach traffic, the width of the intersection and an "average" length of vehicle. The ITE handbook has a discussion of these calulations. I have seen these arranged into charts for convenience. Calculated clearance intervals should always be reviewed in the field and adjusted if necessary.

 

[kaparous]

Thank you teeman
What I meant with the Clearance chart is a chart that usually prepared by the signal designer showing the sequence and display of all of the traffic heads during a complete cycle length, ie green, yellow and red and which phase clears to which phase and so on.

 

[teeman]

We call it a Phase and Timing Chart. It shows the display of each signal head during each phase of operation, and the basic timing parameters (min, extension, max, Y, R)associated with the phase. When properly set up the chart ensures there are no conflicting signal head displays during signal operation.

The manufacturer of the signal cabinet uses the chart to design the cabinet wiring, assigning the signal head wiring to the appropriate cabinet load-switch. The load switches (one for each signal phase)are used to activate the various displays (RYG) in the signal heads. The interval timing is used to program the basic operating parameters.

Our Phase & Timing Chart does not show the signal phase sequence (1-2-3 or other), we utilize a separate phase sequence diagram to illustrate the phase sequence and the organization (single-ring, dual-ring, multiple-ring) of the phases.

Is this helpful?

 

[kaparous]

Definitely yes.
Thank you Leeman