Question. *Redesign and improve the pelican crossing ladder diagram attached by adding timer rungs and counter rungs between rungs 12 and 14 (or any similar workable scheme) together with the necessary contacts inserted in the amber and green man lights of rungs 7 and 10, etc. The chart below shows the required sequence of events. Note that a section of the chart is repeated a total of 16 times. The time intervals are given below. Time period 1 is the ‘normal’ conditions. Time period 2 is after the pedestrian presses the push button. The change from period 2 to period 3 can only be made after at least one five second check of the road sensors. The time interval between 3 and 4 is 4 seconds. The time interval between 4 and 5 is 10 seconds. The time interval between 5 and 6 is 0.5 seconds. The time interval between 6 and 7 is 0.5 seconds. It is not necessary to show the whole of the traffic light ladder diagram shown, only rungs which have been modified. There must, however, be a comprehensive explanation of the operation of the modified rungs accompanying the modified ladder diagram.
Ladder Diagram of pelican crossing.