How to calculate the grounding bus in lightning protection grounding room?

It depends on the distance, the number of grounding items, etc. , generally 16 or 25, but not less than 16. For example, there are 16 street lamps on the street lamp road. Their grounding is respectively connected to the grounding wire with a diameter of 2.5 on the bus. Then the bus at 25 will be almost there. What questions can I ask?