[Cryptography] How to crypto secure speed limit signs

[Bill Frantz]

Wet blanket time:

There are a few system requirements which are being missed by 
some of the commentators.

* The system will have to support old technology for a long 
time. I still occasionally drive a 1939 truck. It doesn't have 
seat belts. It does have a manual choke. (I think the first self 
driving car feature was automatic spark advance, which the '39 
does have.)

* It may well be that a majority of the drivers will not support 
the system with the current speed limits. I drive a lot in 
California. The highway patrol has stated that they focus their 
speed enforcement on roads with a high accident rate. In 
practice, it is frequent to have the only cars going at or below 
the speed limit be the ones with out of state license plates.

* GPS may not be good enough to separate the 70 MPH freeway from 
the 45 PH service road running next to it. As my GPS maven son 
says, "GPS isn't good enough to get you back to your car. It's 
good enough to get you back to the parking lot."

* The system needs to fail operational. Even Ford recognizes 
this fact by allowing a firm press of the accelerator pedal to 
override their system. Being speed limited while trying to pass 
on a 2 lane highway sounds suicidal.

* Any solution which involves printing signs as they are erected 
needs to deal with the problem of sign lifetime in the hostile 
environment of weather and sunlight.

* Any solution needs to deal with the jurisdictions which use 
speeding as a revenue source.


BTW - I really like the slow speed limit sign on the bumper as a 
tailgater hack.

CHeers - Bill

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