Tom, I haven't figured out how to post links here yet (sometimes computer dumb). Do a yahell search on [ Manual on Uniform Traffic Control Devices ] (or MUTCD), and make sure the one you review is the 2009 edition. Sure was an eye opener for me! Ever heard the phrase ' eating crow '? Like I said, sure changed a lot in 16+ years when I worked on them..... A note of caution, its a LOT of READING with many applications, so make sure your in the right section for the situation your reviewing.

Cannot figure out why they are not standardized... The two second rule works at any speed, same as following too closely. If you follow someone at a minimum two second interval, you'll stop safely (given your not distracted, of course)...