Speed radar DIY Arduino

Good morning all,
I would like to build a radar to measure the speed of motorcycles and be able to display it on the edge of the track.
I have seen several similar projects on the net and it seems that the one that consumes the least is made with an arduino.
Currently I am trying to determine if it would be better to use a LIDAR sensor or a DOPPLER. The radar must be placed about 40 meters from the motorcycles for a question of safety and visibility of the speed display. My constraint is also the price because I am doing this for an association. If anyone has done this before or is able to help me out, I’d really appreciate it.

Thank you all.

@Ricco91 Quite a specific project, so not sure if anyone here has experience doing that. Regarding the choice of technology, Lidar / laser should be fast enough, but have not had any experience with Doppler to provide any advice. You could also use two laser sensors separated by a distance and see how long it takes for the front of the car to cross each.