I have to agree with Apskip; it's too dangerous for TPTB to allow possibly tired and definitely determined people to race across the streets of America in pursuit of a million dollars. 
I dislike random taxis as well, which why I have proposed in the past that TPTB should hire three competent drivers who know what they're talking about to drive teams around for the entire leg.
Give each team a map and let them direct the drivers how to get there. It would be the same as if they drove, but safer.
Excellent idea, navigation skills should be an essential part of the race. They could actually do that in most places, except maybe where the script is wildly different like in China or Japan.
I still think they could use public transport more on the race too. Go to some places that have an excellent public transport system. It can create a lot of drama having to catch a bus or train before it leaves, also there would probably be more interaction with local people. And as public transport will probably play a bigger role in transportation systems in the future it would be forward thinking.
