I also would be interested in building a speed detector (i.e for detecting car speeds).  My brother has a radar gun similar to what the police use, which he uses for measuring snowmobile speeds, so I would have something to reference for building a case and actual speed calibration.

Hi.
Unfortunately, at the moment I don’t have any tutorials about that sensor.
I’ll order new parts in the next month, so I’ll add an RCWL-0516 to my list. Hopefully, I’ll manage to come up with a tutorial soon.
Regards,
Sara

Thanks for putting it on your list.  It does sound like an interesting module.
I Googled radar speed detectors and I’m not sure if that module would work for that function.   From what I read, that module appears to be another alternative to using a PIR module.   I think a radar speed detector requires a module that could do the Doppler radar effect measurement.

Hi.
I haven’t searched much about that module yet.
But some people have suggested using it as an alternative to the PIR motion sensor as you’ve described.
 
However, I read the following, so it seems it might be appropriate for radar:

The RCWL-0516 is basically a motion detection sensor. It can recognize motion via doppler microwave technology with the help of walls or other materials. It will be triggered not only by the presence of people but also by other active objects.
RCWL-0516 sensor utilizes the Microwave Doppler radar technology to recognize active objects. The Doppler radar operates by transferring a microwave signal to a target and then monitoring the change in the frequency of the returned signal.
The imbalance in the received signal frequency can also support to estimate of the target’s velocity with respect to the radar.

Source: https://create.arduino.cc/projecthub/hiotron/rcwl-0516-doppler-radar-sensor-interfacing-with-arduino-4c6ef0
 
Regards
Sara