These signs were originally specified in the 1961 Manual on Uniform Traffic Control Devices to provide a standard set of signs to deal with a possible nuclear attack on the United States. Guess the agencies who formulated the MUTCD figured the end of the world would be only a moderate inconvienience(be sure to forward yer mail and take yer charge cards!!). This sign series has survived to the present day but has been modified to deal with more benign natural disasters, mostly. This isn't a joke, these signs are scans from part 6 of the 1961 MUTCD.

CD-1(EM-1): Evacuation Route Marker I actually recall seeing this one in Barber's Point Naval Air Station in Hawaii; on the right is today's version that I've seen in Westchester County, NY for evacuation routes in coastal areas. Oscar Voss has a live Hawaiian one here.

CD-2(EM-2): Area Closed Sign This was to be posted near an area rendered unsafe by nuclear or biological contamination. Basically, it can be used in any area that's not safe after a disaster. It was not to be used as barricade unless adequate advance warning was given.

CD-3(R1-1 and EM-3): Traffic Regulation Post This sign would be used at control points near a targeted area, or today a disaster site. Unauthorized/Non-Emergency traffic would be turned back at these points.

CD-4(EM-4): Emergency Speed Sign "The MAINTAIN TOP SPEED SIGN may be used on highways where radiological contamination is such to limit the permissible exposure time for occupants of vehicles passing through the zone." In other words you have carte blanche to drive like hell, and in this case-you'd WANT to.

CD-5(EM-5): Priority Permit Sign Basically advance warning for CD-3 above. This was to be posted at junctions before a traffic regulation post, to warn non-priority trafffic to turn back, and not add to the burden at

CD-6(EM-6 & 7 series): Emergency Aid Centers Pretty self-explanatory. These signs were to be posted as needed to direct people to emergency services after the bombs dropped. Alternate legends include MEDICAL CENTER, WELFARE CENTER and REGISTRATION CENTER. CHEMICAL SHELTER(with the radiation trifoil, oddly) is the alternate legend for the EM-7 Series.