Road designation or abbreviation

Tunisian A4 motorway with road sign reading A4 road designation

A road designation and a road name abbreviation are easy ways to refer to a road.

The road designation can be created from the original road name or constructed from the road type and number. Road designations are used especially to have a non-ambiguous system of labeling roads on maps and road signs.

Use of letters

Letters are often used in road designations to indicate a class of roadways, which are distinguished from each other by a road number. The way such letters are used depends on the country or other political jurisdiction which contains and controls the road. For instance, among A1 motorways, the one in Spain has a minus sign between the A and the 1 (Autovia A-1) while in Germany the Autobahn 1 is written A 1, with a space between the A and the 1. In Argentina there are zeros between the A and the 1 (Autopista A001).

Single-letter abbreviations

"A" may mean "motorway" in a number of countries (ex. Autoroute in France or Autostrada in Italy, e.g. A14 Autostrada Adriatica), usually the largest and highest-quality roadways in the country
"B"
"C" may mean county in the US
"D" may mean "départementale" in France or "Diaľnica" in Slovakia
"E" may mean "European" road or "Expressways" in Zimbabwe
"F"
"G"
"H" may mean "Hawaiian Interstate" in the US
"I" may mean "Interstate" in the US
"J"
"K" may be used for a state highway in Kansas in the US
"L"
"M" used for motorways in the United Kingdom and Australia, metropolitan routes in South Africa, municipal roads in Portugal, and also used for state highways in Michigan in the US
"N" may mean "national" road
"O"
"P"
"Q"
"R" may mean "regional" route in South Africa and Portugal or "ring" road or "Rýchlostná cesta" in Slovakia
"S"
"T" T roads in Malaysia are roads in Terrengganu; in some parts of the U.S., they are township roads
"U" may mean "unclassified" road; also used in Utah routes in the US
"V"
"W"
"X"
"Y"
"Z"

Multiple-letter abbreviations

BAB: Bundesautobahn (federal motorway) in Germany
BR: Brazilian Federal Highway
CH/CR: County Highway, Route or Road in the US or Canada among other countries
IC: Itinerário complementar (complementary route) in Portugal
IP: Itinerário principal (principal route) in Portugal
SH/SR: State Highway, Route or Road in New Zealand or the US
TH/TR: Township Highway, Route or Road in the US
US: United States Numbered Highway

Road systems

Depending on the country, the letter attributed to a road may be part of a road grading system, be a shortening for a type of road especially in a foreign language or refer to a geographical zoning system, such as the Appalachian Development Highway System or the county highway systems of California, Iowa, and Michigan in the United States.

Existing road systems

International systems

AH roads in the Asian Highway Network
E roads in the International E-road network in Europe

National systems

Australian M, A, B, C, D system

M is for primary roads, A for single carriageway interstates, B for secondary highways, C for roads linking small settlements and D for unsealed roads linking very small remote towns.

British M, A, B, C, D, U system

M stands for "motorway" while A, B, C, D are grades of roads, and U means "unclassified".

Chinese G, S, X, Y system

G stands for national highway and S is for provincial roads. X and Y are for local roads between counties and villages.

Cyprus A, B, E, F system

A stands for motorway and B is for main roads. E and F are for smaller local roads.

French A, N, D system

A stands for "autoroute" (motorway), N for "national road", D for "départementale" road and C for "communale".

German A, B system

A stands for "Autobahn" (motorway), B for "Bundesstrasse" (federal road).

Jamaica A, B system

Netherlands' A, N system

A stands for "Autosnelweg" (motorway), N for Non motorways. The A-codes use white letters on a red shield, the N-codes black letters on a yellow shield. Where a highway changes into a motorway or vice versa, it may continue to use the same number, but the letter and the color are switched.
When the letter is followed by three digits, the road is typically a provincial road. When there are only one or two digits, it is typically a national road.

Senegal N, R system

N stands for "national" roads while R is for "regional" roads.

Slovak D, R system

D stands for "diaľnica" (motorways) while R is for "rýchlostná cesta" (expressways).

South African N, R, M system

N stands for national road, R stands for regional road and M stands for metropolitan road.

Vietnamese QL, TL, HL system

QL stands for quốc lộ (national road); TL and ĐT stand for tỉnh lộ and đường tỉnh (provincial road); HL stands for hương lộ or huyện lộ (rural district road); and ĐCK stands for đường cặp kênh (canal towpath).