Aluminum has become the guiding hand for American's highway traffic. Used for auto license plates since the mid-1940s when Connecticut issued the first car tags using the metal, aluminum now is relied on for most of the traffic-regulating signs directing motorists on both the Interstate Highway System and other state roadways and city streets.
A major factor in the popularity of aluminum among highway department officials is the normal long life of such signs. Ease of maintenance and handling, recyclability and lower costs are other factors in the demand for aluminum signs.
"Except for vandalism, our signs and the faces last from seven 10 years," says Ed Blodgett, traffic operations engineer for the State of Washington.
Long life is also a major reason why m ost car license plates today are aluminum. State tags normally last for many years, cutting manufacturing costs because plates for every registered vehicle do not have to be produced every year. A paste-on tab usually validates long-life tags from year to year.
In Montana, Idaho, and Washington from 70 to 95 percent of all road signs are made of aluminum, with some 75 to 80 percent of Oregon's signs using the light material.
The trend is even higher on the East Cast. highway officials in New York, New Jersey, Virginia, and Florida, for example, report the use of aluminum for road signs to be virtually 100 percent.
While highway travel is less today than in former years, the use of road signs continues to grow, because the public demands better road directions.
The various state highway departments usually ask for yearly bids for blank aluminum signs, in the various shapes and sizes with which every driver is familiar, square, oblong, round, and -- for interstate Highways --
The blanks are then covered with a special reflective sheeting on which a silk screening process is used to print the messages for the public. This is the only work required on the blanks, unlike plywood signs used in some places. The plywood sign must be trimmed and given a sealant before the message can be emplaced.
Glen Clark, investigations and research engineer for the Oregon Department of Transportation, said his state went to aluminum because "we wanted something that would last as long as the roads" but added that there have been some problems with the coatings "which still do not last as long as we would like."
Replacement of most highway signs is necessitated by vandalism, especially in areas where hunters take frequent pot shots at the signs.
Some idea of the national market for these highway markers can be gained from the remark of Canute Knudsen, a painter in the sign shop of Multnomah County, Ore., that you're talking about replacing 8,000 to 10,000 signs every year" in his county alone, while the City of Portland replaces some 20,000 every 12 months.
Nor is aluminum restricted to the smaller directional signs at roadside level. Extruded aluminum bolted together in 12-inch increments is used to build signs -- for overhead use, usually -- to virtually any size, up to 30-feet square.
Those reflective buttons found on the signs and on many roads, some of which convey messages to the motorist, also are made of aluminum.
Highway officials emphasize that highway sign vandalism "cuts down the readability factor" and so reduces the safety factor.
Oscar Wright of the oregon Highway Department says if anyone gave a thought to the accident potential in vandalized signs, they might "think twice before they spray-painted a sign, shot at it, or removed it because it might look nice in their bedroom."