Road signs are necessary to keep drivers and pedestrians safe, informing them of traffic direction, speed limit and many other important factors on any given stretch of road. They must be either illuminated or have a reflective surface. One of the most important road signs is the universal stop sign. Other common signs include construction signs, school zone signs (often declaring a reduced speed limit) and signs that point the way to hospitals.
Safety signs are regulated by the Manual on Uniform Traffic Control Devices. This guide details how each sign should look and what its dimensions should be. Road signs are usually made from plywood, steel or aluminum cut to the desired shape. The letters, numbers and symbols are cut from retro-reflective material which will catch a driver's eye.
Before the blank material can have the background color (sheeting) applied, it must be inspected for dirt. Many manufacturers check for grime by putting a piece of tape down on the surface and then ripping it back up. If the tape comes up transparent with no specks of color, the sign is free of dirt. Wax and grease can also be problems, and this is checked by pouring water on the sign. If the water beads up or changes course, the sign must be cleaned. Any grease can be removed with naptha or mineral spirits.
Once the blank is completely ready, the background sheeting is cut either one at a time by hand or several at a time by machine. The letters, numbers and symbols can be manufactured by a die-cut machine or punched out by hand.
The background sheeting is applied via the adhesive on its back and then the sign is put through a roller that gets rid of any air bubbles. The next step is to heat the sign so the adhesive will bond. This occurs in a heat lamp vacuum machine. After the background screen has cooled, the letters and numbers can be applied. Air bubbles can be eliminated by using a squeeze roller or a hand roller. Next, the sign is heated again, this time with a slip sheet covering the entire unit.
The material out of which the traffic sign is made is important. Plywood is inexpensive, but it can degrade rather quickly. Steel is an option for mid-range budgets, but can rust unless it is treated with zinc. Aluminum is the priciest choice, but it will never rust. Each of these factors is important to consider.