I can't say, for sure, what was in the driver's mind... but, I think he believed that, by signing the ticket, he was admitting guilt. And, he didn't want to admit guilt.
Based on the timing of when they passed the Speed Limit sign, and when the stop was made... I'd say it WAS unlikely that he was speeding when he passed THAT sign. It sounded like the officer said there was ANOTHER sign... further back. Perhaps the driver didn't see or know about that sign.
Had these two engaged in anything like communication, perhaps this could have been explained. Had the driver KNOWN that signing was NOT an admission of guilt.. maybe, he would have signed. We'll never know. Because, this cop was not going to take ANY guff.... He was taking him to jail. WHY?? Why was he is such a hurry to take this man, who is so obviously NOT a threat... to jail? YOU answer that one.
Meanwhile the jails are overflowing and we have early releases for pedophiles, murderers, rapists, and drug dealers.
Brilliant move by the trooper. Simply brilliant.