Is Your GPS Naive?

mi writes "Many GPS devices today will try to scan the FM bands for traffic advisories in the area to display on their screens. The signals, however, are neither authenticated nor encrypted, and one can — with commonly available electronics — construct a device to broadcast bogus advisories. Possible codes range from "bullfight ahead" to "terrorist attack"..."

Comments

Re:Social hack - use "bullfight" for "speed trap".

[fractoid]

Do you really expect someone to go out to each road, and try and determine the fastest allowable speed? It is a lot easier (cheaper) just to say, every one of these roads has X for a speed limit. Oddly enough, they don't seem to mind putting in the effort to *police* speed limits.

If we assume that each road will have a speed trap on it at least once, then they've *already got* the data to determine an appropriate speed limit as per the 85th percentile rule. Interestingly, as Wikipedia notes, "a review of available speed studies demonstrates that the posted speed limit is almost always set well below the 85th-percentile speed by as much as 8 to 12 mph (see p.88)." This indicates that in a vast majority of cases, speed limits are set according to political rather than safety concerns.