Although contestants are shown leaving the cab with cash in hand, they are actually sent a check in the mail.
No contestants know that they are entering the "Cash Cab", but some contestants are pre-picked and told that they are taking the cab to the location of shooting of a different show. All others are randomly selected while trying to hail a taxi.
The "cash cab" is a licensed New York taxi.
Episodes in the second season move faster due to the more strict time limit allotted to answer the questions.