Total nerd's speculation...
I suppose they could require a standard transponder ID on the vehicle. It would be tuned to the, say, Ka band radar frequency. When hit by traffic radar, it reflects with a message of its ID.
When a cop runs his radar unit, instead of displaying Fastest or Strongest, it displays a list of the speeds, and their associated IDs, for all vehicles in the radar beam. No more taking the blame of some other speeder in your lane.