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.
Very problematic. How does the vehicle know which pole to talk to? How does it know it’s not incorrectly communicating with a pole on a parallel or perpendicular road, for example? Or indeed a road that is below another road, as sometimes occurs in urban environments. So so so many issues. How does the vehicle reliably know which road it’s on? How is the system kept invulnerable to bad actors? Etc etc
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.
I don’t agree with the proposed solution being entertained here, but all of these problems are solved. Because automated tolling systems work this way.
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.
There is no security at all on many infrared traffic signal overrides. You can easily hack them, you just have to decide if it’s worth the risking being charged with a crime that carries a minimum 6 month prison sentence.
How would that work? Cell phones record your location as a side effect, because they can be seen by multiple cell towers.
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.
Now I can only imagine fun times when those get stolen from road works... And then relocated to some other places. Maybe just simple plastic bag used to cover the number...
padolsey|2 years ago
samtho|2 years ago
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.
kube-system|2 years ago
dmitrygr|2 years ago
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.
kube-system|2 years ago
thaumasiotes|2 years ago
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.
Ekaros|2 years ago
crossroadsguy|2 years ago
Rebelgecko|2 years ago