A busy intersection needs to upgrade the current 3-light 3-state traffic light system (see illustration below) to a 4-light 5-state system to address an increasingly heavy demand for left turns. A computer simulation needs to be developed as a proof of concept.

Looking at the light that is red, we see the cars are stopped, waiting for the light to turn green. If 5 of more cars line up, the car sensor will signal the light to turn green sooner, as described below. The pedestrian who wants to go in the same direction as the cars stopped on the red light is also stopped. If the pedestrian presses the walk button on the light pole, this will also decrease the wait time for the red light as described below. The 4 lights in the new system are as follows: 1. Red 2. Amber 3. Green 4. Advance left turn (Green to Amber) 4-Light 5-State Traffic Light: Sequence of states The sequence of a 4-light 5-state system is shown in the above illustration. Below are the 5-states including the time duration for each state: 1. Solid Green + Advanced Left Green Arrow [15 seconds] 2. Solid Green + Advanced Left Amber Arrow [5 seconds] 3. Solid Green + Advanced Left Arrow (off) [45 seconds] 4. Solid Amber [10 seconds] 5. Solid Red [?? seconds YOU FIGURE THIS OUT ] APS145 Applied Problem Solving Page | 3 Additional Features Request-To-Walk Button A button is provided for pedestrians to press to alert the system a person needs to cross. This is only effective when the lights are in a red-light state. This request will reduce the remaining wait time of the red-light state to 10 seconds. Car Sensor There is a sensor mounted on the light fixtures that monitors the number of waiting cars when in a red-light state. When the number of cars waiting reaches 5 or more, the sensor will trigger the system to reduce the remaining wait time of the red-light state to 10 seconds. Interrupt The defined system should take in to account an interrupt. This is something that can occur at any time and will take over/supersede the active state. Examples of this type of interruption can be the traffic controllers setting all lights to flash amber (for caution) or to flash red (4-way stop) etc... You dont need to specify what the interrupt should do only account for it by checking if there is an interrupt to the normal process flow and how the system should resume when the interrupt has completed.

Work Breakdown [Logic 1] Define a standard 3-light system (red, green, amber) with an interrupt (no advance green, request to walk, or car sensor). The light durations are: Green=40 sec., Amber=15 sec., and Red=? [you figure this out].

[Logic 2] Define a standard 3-light system (green, amber, red) with no advance green, request to walk light, car censor, or interrupt. The light durations are: Green=45 sec., Amber=10 sec., and Red=? [you figure this out].

[Logic 3] Define a red-light waiting sequence (do not include the other light states) with a request to walk button and a car sensor. Determine the red light duration if the following durations are applied to the other light states: Green=50 sec., Amber=5 sec.

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