United States of America/Signage
Traffic signing in the United States is based on a system which uses white-background rectangles for most regulatory messages (other than STOP and YIELD), yellow-background diamonds for most warning messages, green background for guide signs (directional signage) regardless of road class, brown background for tourist attractions, blue background for services, and orange background for construction-related messages. Most signs are rectangular (square or oblong) in format. The US has a bicolour pavement (road surface) marking system; white is associated with movement in the same direction and so is used for lane stripes on multilane roads, while yellow separates opposite directions and so is used for centre lines, median islands (central reservations), etc
The ultimate authority for traffic signing in the United States is the Manual of Uniform Traffic Control Devices (MUTCD), which is prepared by the US Federal Highway Administration (FHWA). However, traffic control is delegated to the states; FHWA's authority to set national standards is based on partial federal funding of highways. States are allowed to have their own traffic manuals ("own-manual states") or to have their own MUTCD supplements ("supplementers") in lieu of adopting the federal MUTCD ("direct adopters"), so long as the state MUTCD or MUTCD supplement is in "substantial conformance" with the federal MUTCD. In general, the design of warning and regulatory signs is well standardized across the US while there is more variation in the design of guide and informatory signs.
Design details for signs are given in Standard Highway Signs, a companion publication to the MUTCD. A number of states have sign drawings books which function either as supplements or direct replacements for FHWA's SHS. As a generalization, the US relies more heavily on word messages than most European countries, although the immense number of word-message signs in SHS and its state-level equivalents obscure the fact that symbolic signs are very heavily used while the vast majority of distinct word-message signs are not often seen.
In contradistinction to Europe, guide signing in the US relies heavily on special markers for numbered highways, which are typically (but not always) maintained by a state's Department of Transportation (DOT) and function as an equivalent to the road classification system in the UK. These special markers, called route markers or route shields, are done to distinct designs for Interstates, US highways, and state routes, and appear either by themselves or on larger green-background guide signs. The design of state route markers generally varies from state to state and is often an expression of local identity (e.g. the sunflower for Kansas, the miner's spade for California, the Indian head for North Dakota, the Zía sun symbol for New Mexico, the beehive for Utah).
SHS also includes Standard Alphabets for Highway Signs, which includes dimensioned drawings for the typefaces approved for use on American traffic signs. These are known as the FHWA alphabet series and are available in differing levels of condensation, with Series B having the thinnest letters while Series F has the broadest. Series C and D are the most common series on conventional highways while Series E and Series E Modified are generally used on freeways and expressways. Since 2004, American highway authorities have also had the option of using the Clearview typeface family on positive-contrast signs, if they have interim approval from FHWA for this purpose. Like the FHWA alphabet series, the Clearview typefaces come in differing levels of condensation, with Clearview 3-W and 4-W most common on conventional roads while Clearview 5-W and 5-W-R are typically used on freeways and expressways.
In the US, sign mounting standards and reflectorization technologies have historically varied widely among states. As a generalization, however, signs have to be mounted on breakaway posts if they are located in the clear zone and are not protected by a guard irail. Small signs tend to be fabricated of sheet aluminum and affixed to posts by bolts driven through the face of the sign (hanger systems similar to those used in the UK are not in wide use among US states). Large signs tend to be constructed of aluminium extrusions which are then hung from pipework structures or strapped to monotubes. Whole-letter retro-reflectorization is the norm now that button copy (i.e., letters with embedded circular cut-corner prism reflectors) is no longer available; demountable copy is vanishing in favour of direct-applied copy (the UK standard for decades). Unreflectorized backgrounds on guide signs are becoming increasingly rare. Regional variations include the use of plywood or paper laminate for large guide signs. In contrast to the UK, overhead signing on freeways relies heavily on cantilever structures rather than full-width gantries.
- The federal MUTCD and SHS
- California's sign specification sheets, collectively the SHS equivalent
- California's MUTCD
- Richard Moeur's traffic signing site Originally appeared in the late 1990's when the MUTCD was not online; contains many Arizona-specific sign designs since the maintainer manages guide sign rehabilitation contracts for the Arizona Department of Transportation