
The Federal Highway Administration is in the final stages of the review process for the next update to the Manual on Uniform Traffic Control Devices, due out in 2009. (The last update on the traffic control "bible" was 2003, and amendments have been made over the course of last few years.)
A couple of common signs will be removed from the manual (including the legend-based "Stop Ahead" and "Yield Alead" signs, in favor of those that are symbol-based) and several new signs will be making their way to America's highways. One addition is the "No Through Traffic" sign... I am pretty sure this is not the official name for it, and I've always wondered why we never had a sign like this a long time ago. It pretty much looks like a "No Straight" sign - a sibling to the No Left Turn, No Right Turn and No U-Turn sign.
A great example of use for this sign: You come to a 4-way intersection and the street directly in front of you is one-way traffic that flows in the opposite direction you are traveling, which today would be marked with Do Not Enter or One Way/Do Not Enter signs.