The fact that it's US DOT doesn't make them any more right.
I'm sure they lie and make up statistics on turnpike miles all the time. [/sarcasm]
The discrepancy is likely the fact that this appears to be a list of "interstate" toll roads, not all toll roads. Had you read the link, you would have been the one to tell me that. And if you were like Squat, you would have claimed I was "lying" (using the leftist definition of lying, which is anything said by someone that goes against what you want to be true).