Phillip Greenspun has a post up about his desire for widespread WiFi - I'm not sure that it would save fuel the way he thinks - if you examine his side trip thing, for instance, it would take a good amount of time to find the website and get the hours of operation - likely enough time that you would be past the exit (or already off and on the way down the road to the attraction).

That's not the biggest problem though. 802.11x isn't the same kind of protocol as digital cell (GSM, CDMA, etc) use - I've driven through neighborhoods with open wireless all the way down the street - at 30 mph (much less highway speeds) you can't acquire and keep a signal - by the time you get one, you've lost it - there's simply no handoff mechanism. IIRC, WiMax might sidestep that issue by making the coverage area wide enough - but it's not widely deployed yet.

Interestingly enough, the system that currently addresses that problem is one that Phillip addressed in his very next post - Verizon broadband services via the existing cell system. It's slow and expensive - I've read that it works all the way up and down the Amtrak NE corridor, and I figure it might be worthwhile for regular commuters on that route. For anyone else? Panera Bread or Starbucks are simpler answers.

I don't see anyone rolling out a single 802.11x system across the highway system anytime soon - too many nearby homes and businesses would poach off of it if it were free, and the installation costs would likely make the service expensive anyway (just look at the aforementioned Verizon system for an example).