Arduino project · Distance and parking · Hard
Smart Traffic Junction (Queue Priority)
Road A normally has green. When a car waits on road B and none waits on road A, road B gets the green. A car on road A always takes priority.
What you will learn
- How a junction reacts to waiting cars
- How a later rule can give priority
- How smart traffic lights save waiting time
How it works
IR sensor 2 on road B turns road B green. IR sensor 1 on road A then overrides it. A 1.5 s minimum keeps the lights from flickering. LEDs 1 and 2 are road A red and green, LEDs 3 and 4 are road B red and green.
Try this next
- Add yellow lights for a safe change.
- Add pedestrian buttons.
- Use an ultrasonic sensor to measure the queue length.
The simulator program and explanation on this page are original. The idea follows a classic Arduino project that students have built for years.
Parts: sensors and actuators (tap to show or hide)
Try the inputs (virtual sensors)
Pins (you can change them)
| Part | Arduino pin (change it here) | How to wire it |
|---|
Every wire, one by one
Red rail = 5 V from the Arduino 5V pin. Black rail = GND. The coloured wires carry signals. Match the wire colours on the drawing to this list.
| # | Colour | From (part and leg) | To |
|---|
Steps run from top to bottom, then start again. While the simulation runs, the active step is highlighted in green.
Quantities come from the parts you added. The store links open a search for that item on Robu.in, Amazon.in and ThinkRobotics, so you always see what is in stock today. Check the model, voltage and price before you order.
| # | Item | Qty | Search term | Buy / compare |
|---|
The PDF has the circuit sketch, pin table, every wire, sequence, full code, the parts list with store links, do’s and don’ts for each part, and the safety notes. The project file lets you come back and keep editing.
In the real world
A smart city junction
Press the sensors in the simulator and watch the real junction change: road A keeps priority and road B gets the green only when its car is waiting alone.
Tip: use the gold tab at the bottom of the circuit drawing to pull the real-world view up over the Arduino board. Your parts stay visible above it, so you can press a button and watch the real scene react.
- LED 1 and 2 = road A: red and green
- LED 3 and 4 = road B: red and green
- IR sensors = cars waiting on road A and road B