hi,your question is confusing.  More details should be given.

Just count the vehicles in 24 hours?  How far is the distance from the light? .....

maybe,  ultrared  sensor ; RFID; pyroelectric sensor, ......

There are very many ways how to count vehicles - see for example FHWA Traffic Monitoring Guide (https://www.fhwa.dot.gov/policyinformation/tmguide/) or http://ftp.jrc.es/EURdoc/JRC47967.TN.pdf

The simplest way would be to install some pneumatic tubes for two weeks or so. 

Yes, this is one of the methods. But each one has its pros and cons, including the price considerations (staff needed for installing and possibly also observing, in order not to get stolen :-))

I started this type of research, a lot of time ago, using a camera. You have to find the best place for camera and after that to record all traffic. You can count and classify all traffic using this record, in your office. If you want advanced solutions please give us more details.

Dear Akinbode ALANI Owodolu,

you can adopt Doppler and Radar Microwave Sensors.

Doppler microwave detection devices transmit a continuous signal of low-energy microwave radiation at a target area and then analyze the reflected signal. The detector registers a change in the frequency of waves occurring when the microwave source and the vehicle are in motion relative to one another. This allows the device to detect moving vehicles.

Radar is capable of detecting distant objects and determining their position and speed of movement. With vehicle detection, a device directs high frequency radio waves at the roadway to determine the time delay of the return signal, thereby calculating the distance to the detected vehicle.

You can also install a video camera and process the video at the office. 

Since the data is for traffic signal control, it is important to capture all the turning movements at the intersection. The best equipment is a hand held counting device that recognises all turning movements. Other options are expensive in equipment, labour and sorting of data after collection.

Inductive loops are used to count cyclists.