A highway shield or route marker is a sign denoting the route number of a highway, usually in the form of a symbolic shape with the route number enclosed. As the focus of the sign, the route number is usually the sign's largest element, with other items on the sign rendered in smaller sizes or contrasting colors. Highway shields are used by travellers, commuters, and all levels of government for identifying, navigating, and organising routes within a given jurisdiction. Simplified highway shields often appear on maps.
Purposes
There are several distinct uses for the highway shield: Junction signs inform travelers that they are approaching an intersection with a numbered highway. Guide signs inform travelers which way to go at intersections, usually with an arrow pointing the way. These include: Directional assemblies, which combine highway shields with separate cardinal direction signs and arrow signs on the same post, and Direction, position, or indication signs, which include highway shields as part of the sign legend. Reassurance markers are used after major junctions and periodically in between to confirm the route and direction. Trailblazer assemblies are posted on other roadways to "blaze the trail" to the highway in question, usually with a "TO" banner plate above the shield Some jurisdictions place highway shields on highway location markers (kilometre or mile markers). At complex interchanges, route shield pavement markings help motorists get into the correct lane.
Highway shields by country
Australia
Australia has maintained distinctly different trends pertaining to highway shields in the past and will continue in this vein somewhat, despite the conversion to alpha-numeric routes and shields. Alpha-numeric route numbering has been in use in Tasmania since the 1970s, and was introduced in the mainland states from 1996, with the state of Victoria being the first to implement the policy on the mainland.
Prior to this conversion and concurrently, Federal Highway (gold-on-green squared-off bullet), National Highway (black-on-white squared-off bullet), State Highway (blue bullet) and Tourist Route (white-on-brown rounded pentagon) shields existed. In Victoria Freeway shields were used (white-on-green with 'F' prefix) until the late 1980s, while during the 1990s Queensland and New South Wales implemented a hexagonal blue-on-white Metroad system of urban arterial routes. The Western Ring Road (now M80) in Melbourne initially used a shield quite similar to the U.S. Interstate shield, albeit with 'Ring Road' written instead of 'Interstate' and with 2 peaks rather than 3.
To further complicate matters, with the introduction of the alpha-numeric system, roads that are federally funded (or Federal Highways) have a squared-off bullet encompassing the alpha-numeric designation. Freeways and dual-carriageway roads often use an 'M' prefix, particularly in Victoria. In addition, trapezoidal signs are placed every 5 km on major regional highways and freeways indicating the distance to the post office of the next city or major town on the route. These signs usually only have the first letter of the destination; two or three letters are used if there is ambiguity between nearby towns or when the place name consists of two words.
Brazil
Federal and state highways shields are standardized in Brazil by the National Transit Department (DENATRAN), but implementation is not always consistent nor even existent. In many states, highway names appear on highway location markers and guide signs with no highway shield.
Canada
Each province dictates the type of shields used as highway transportation is a provincial responsibility. However, the green and white signage for the Trans-Canada Highway is used nationwide. Each province has their own shape for the sign, though.
Alberta
Shields for core highways in Alberta use black route number on a white squared-off bullet, while shields for local highways (500-986) use black route number on a white oval. Both variants feature the provincial wordmark across the top, although it may be omitted on certain guide signs.
British Columbia
Standard shields for highways in British Columbia use blue route number on a white bullet, with the provincial shield of arms placed at the top. Certain highways (e.g. Crowsnest Highway, Southern Yellowhead Highway and Nisga'a Highway) use their own variations on the default provincial highway shield.