Not necessarily. The vehicle can communicate with the speed limiter pole to obtain the speed limit and adjust its speed accordingly. There are no cameras, no GPS, and the speed limit can be set dynamically.
The RF method works the same way ILS for aircraft works: multiple lobes of differing frequencies to a compatible receiver that will only accept the data if both frequencies are present and the interference pattern matches the conditions that it is looking out for.
IR is considerably simpler and would require a receiver to pick up on a well-aimed beam.
For bad actor mitigation, they could put a signature at the end of the speed data that signs the packet with the priority, route, datestamp, and TTL. The priority field could help enforce slower limit around construction zones.
The suggested mandate is for all roads, which introduces crosstalk errors in the system decoding the environment.
As a person who's reverse engineered O(1000) "secure" devices and O(100) "secure protocols", let me just laugh aloud at the thought that this will be done right!!!
Basically: new fun use for SDR just dropped! Randomly broadcast speed limits of 1mph near the higway.
But in this scheme, your car would record your location as the primary effect. You can still see multiple limiter poles. How do you know which one applies to you? You need to determine your location for that. (Unlike with cell phones, the pole with the strongest signal is not necessarily the one that applies to your position.)
If the limiter poles can receive as well as broadcast, they will also record your location, just like cell towers do. But even if they can't, it's necessary for the car to do so itself.