I have done this on my own already via mybiketraffic.com, but I think this would be a feature that Strava users would love to see directly on Strava. I am happy to share code and help work with your developers to bring this feature to life. Here's an example ride map showing where cars passed and how fast a particular car was going during the 10 seconds it took to pass me (from when it first appeared on the radar) -
Speeds of a car during its 10 second pass. Speed readings are measured every second.
Feel free to reach out to me via DM or through this discussion. Thanks!