A project that combines traffic signals and car over-speed detection using an Arduino Uno can be an interesting and educational endeavor. Here's a basic outline of how you could approach such a project:

Components Needed:
1. Arduino Uno board
2. Ultrasonic distance sensor
3. LED lights (for the traffic signal)
4. Buzzer (optional, for audio alerts)
5. Jumper wires and breadboard (for circuit connections)

Project Steps:

1. Set up the Arduino Uno:
Connect the Arduino Uno to your computer using a USB cable.
Install the Arduino IDE software if you haven't already.
Ensure that you have the necessary drivers installed for the Arduino Uno.

2. Connect the components:
Connect the ultrasonic distance sensor to the Arduino Uno. Use the sensor's VCC, GND, and signal pins, and connect them to the respective Arduino pins.
Connect the LED lights to the appropriate pins on the Arduino Uno. Assign different pins for each color (red, yellow, and green).
Connect the buzzer (if using) to a digital pin on the Arduino Uno.

3. Write the code:
Open the Arduino IDE software and create a new sketch.
Write the code to read the distance data from the ultrasonic sensor.
Implement a logic to determine if a car is overspeeding based on the measured distance and a predefined threshold. For example, if the distance suggests a car is moving too fast, trigger an alert.
Write code to control the traffic signal lights based on the car's speed. For instance, if the car is overspeeding, switch the signal to red.
Add any additional functionalities, such as audio alerts with the buzzer.

4. Upload the code to the Arduino Uno:
Connect the Arduino Uno to your computer via USB.
Select the appropriate board and serial port from the Arduino IDE menu.
Click the "Upload" button to upload the code to the Arduino Uno.

5. Test and calibrate:
Mount the ultrasonic sensor and set up the LED lights to mimic a traffic signal.
Test the project by moving an object (or your hand) in front of the ultrasonic sensor, simulating a passing car. Observe if the appropriate LED lights are triggered based on the car's speed.
Adjust the speed threshold and other parameters in the code to ensure accurate detection and signaling.

Remember to take necessary precautions while testing the project, especially if you're working with real vehicles or roadways. Additionally, this project serves as a basic example, and you can enhance and expand it based on your requirements and creativity.