During a job interview for a position that relates to traffic engineering, interviewers may ask you to explain your understanding of traffic light systems. While answering, it’s important to discuss the concepts and key elements that create a safe intersection. Understanding how to explain the traffic light system design process may help you to show your knowledge and qualifications in traffic engineering. In this article, we discuss why interviewers may ask you how to design a traffic light and provide steps to help you answer the question effectively.
Ep 063: Introduction to State Machines: Designing a Simple Traffic Signal
Example answers for “How do you design a traffic light?”
Here are three examples of answers to the question, “How do you design a traffic light?” to help you better prepare for your interview:
Use keywords
To show your familiarity with traffic-design concepts and safety regulations, consider using engineering keywords that may get the hiring managers attention. By doing so, they may recognize that youre a well-qualified and knowledgeable candidate. Here are some examples of keywords that you may use to discuss traffic light system designs:
Example 1
“To begin, I first observe traffic footage of the intersection where we are placing the new traffic light system. If theres an existing light system, I look for areas of improvement within the traffic flow and light cycles. If there isnt a light system, I begin thinking of ideas to increase motorist and pedestrian safety and I analyze the intersections lanes, traffic and pedestrian frequency and local landmarks that may cause higher traffic during the day. Then, I review the traffic patterns to understand which light cycles may lower the chance of slow traffic.
Next, I create a design that matches the areas basic traffic and safety needs. To do so, I program a system to use a set number of signals based on the feedback that the systems receives from the trigger points within a road. After testing this model to ensure the trigger points provide effective feedback, I program a timer that ensures that each light at the intersection coordinates with a timer that changes the signals automatically to lower the flow of traffic in the opposite direction.”
Example 2
“To create a safe and effective traffic light system, I first determine the amount of vehicle and pedestrian traffic in the area. To do so, I review traffic footage, which also helps me create a list of traffic flow requirements, including the length of each light cycle and pedestrian crossing time. I also review the time that it takes for a group of vehicles to clear an intersection fully so that I can better understand how long to program the timer before transitioning to a new signal.
When programming a light, I first input the proper traffic signals that respond to feedback from trigger points. Then, I program a timer to allow for 20-30 seconds between signal transitions, depending on the size of the intersection and the time it takes a vehicle to cross it. Before implementing the light system within an intersection, I ensure to select a placement for the traffic light that allows enough room for pedestrians to cross the street and to ensure that the system is visible to motorists.”
In this blog, I will explain the concept to design a traffic light system, using a Design Pattern like State Design Pattern.
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No GUI is required, only system logic is considered, and program running results can be displayed in Log mode.
Compared with traditional threads, the use of thread pool improves the performance of the system, and users do not need to care about which thread is executed
Each Road object has a name member variable to represent the direction, and a vehicles member variable to represent the collection of vehicles in the direction. In the construction method of the Road object, start a thread to add a vehicle to the vehicles collection at random intervals (represented by a string in the form of “route name_id”). Start a timer in the construction method of the Road object and check whether the light in the direction is green every second. If yes, print the vehicle collection and remove the first car in the collection.
The traffic lights cannot be green on both roads at the same time. That means when the light is green on road A, it is red on road B and when the light is green on road B, it is red on road A.
Initially, the traffic light is green on road A and red on road B. When the light is green on one road, all cars can cross the intersection in both directions until the light becomes green on the other road. No two cars traveling on different roads should cross at the same time.
Your answer is considered correct if it avoids cars deadlock in the intersection. Turning the light green on a road when it was already green is considered a wrong answer.
There is a traffic light located on each road before the intersection. A traffic light can either be green or red.
There is an intersection of two roads. First road is road A where cars travel from North to South in direction 1 and from South to North in direction 2. Second road is road B where cars travel from West to East in direction 3 and from East to West in direction 4.
FAQ
How do you design a traffic control system?
How do you make a traffic light controller?
