One solution is to add redundancy. A stop sign, for example, could broadcast a low-power radio signal, and be accompanied by a retro-reflective strip with a coded pattern on the side of the road leading up to it, and emit tones at particular ultrasonic frequencies…
GPS could be a part of this, but it's easy to imagine what could go wrong. Somebody mistakenly installs a stop sign without updating the database. Another person makes a mistake configuring a cache parameter and the CDN starts serving up last year's map. There's a whole class of problems eliminated by keeping the information local. Imagine if you had to drive looking only at road information served over the internet -- would you trust it?
GPS could be a part of this, but it's easy to imagine what could go wrong. Somebody mistakenly installs a stop sign without updating the database. Another person makes a mistake configuring a cache parameter and the CDN starts serving up last year's map. There's a whole class of problems eliminated by keeping the information local. Imagine if you had to drive looking only at road information served over the internet -- would you trust it?