A permanently signed detour route (also known as an emergency detour route or emergency diversion route) is a type of route which is used temporarily during special circumstances. Various areas have developed these systems as part of
incident management. The purpose of these routes is to provide a
detour
__NOTOC__
A detour or (British English: diversion) is a (normally temporary) route taking traffic around an area of prohibited or reduced access, such as a construction site. Standard operating procedure for many roads departments is to route an ...
in the event that the parent route is impassable, due to either a
traffic jam
Traffic congestion is a condition in transport that is characterized by slower speeds, longer trip times, and increased vehicular queueing. Traffic congestion on urban road networks has increased substantially since the 1950s, resulting in m ...
s,
traffic collision
A traffic collision, also known as a motor vehicle collision, or car crash, occurs when a vehicle collides with another vehicle, pedestrian, animal, road debris, or other moving or stationary obstruction, such as a tree, pole or building. Tr ...
, or road closure (for a variety of reasons). Sometimes these routes are signed as a prefixed or suffixed
numbered road, making them a type of
special route
In road transportation in the United States, a special route is a road in a numbered highway system that diverts a specific segment of related traffic away from another road. They are featured in many highway systems; most are found in the Inte ...
.
A permanently signed detour route should not be confused with a "permanent detour". The latter would be used if a particular roadway section, such as a bridge, were closed permanently.
Australia
Sydney

The state of
New South Wales
New South Wales (commonly abbreviated as NSW) is a States and territories of Australia, state on the Eastern states of Australia, east coast of :Australia. It borders Queensland to the north, Victoria (state), Victoria to the south, and South ...
in Australia has signposted 'D' and 'D1' detour routes on the
M1 Pacific Motorway M1, M01 or M-1 may refer to:
Arts, entertainment & media
* M-1 (rapper), one half of hip hop duo Dead Prez
* Korg M1, a keyboard synthesizer
* Leica M1, a 1959 35 mm camera model
* Olympus OM-1, a 1972 manually operated 35mm single-lens ref ...
between
Newcastle
Newcastle usually refers to:
*Newcastle upon Tyne, a city and metropolitan borough in Tyne and Wear, England, United Kingdom
*Newcastle-under-Lyme, a town in Staffordshire, England, United Kingdom
*Newcastle, New South Wales, a metropolitan area ...
and
Sydney
Sydney is the capital city of the States and territories of Australia, state of New South Wales and the List of cities in Australia by population, most populous city in Australia. Located on Australia's east coast, the metropolis surrounds Syd ...
and the 'D5' for the
M5 East in the case of temporary road closures.
Canada
Ontario

The province of
Ontario
Ontario is the southernmost Provinces and territories of Canada, province of Canada. Located in Central Canada, Ontario is the Population of Canada by province and territory, country's most populous province. As of the 2021 Canadian census, it ...
in Canada is one jurisdiction outside the United States with a very prevalent system of these roads. The ''Emergency Detour Routes'', originally ''Emergency Diversion Routes'' (EDR), are a system of temporary detour routes paralleling many
major highways in
Ontario
Ontario is the southernmost Provinces and territories of Canada, province of Canada. Located in Central Canada, Ontario is the Population of Canada by province and territory, country's most populous province. As of the 2021 Canadian census, it ...
. Most of these follow
county or municipal roads within the province that are not (currently) provincially controlled (though many were
former provincial highways). These routes are designed to be used in the event of a closure on a major road or
400-series highway
4 (four) is a number, numeral and digit. It is the natural number following 3 and preceding 5. It is a square number, the smallest semiprime and composite number, and is considered unlucky in many East Asian cultures.
Evolution of the ...
, such as construction or serious collisions.
Though most EDRs are set up along 400-series highways, a select few have been established along two lane King's Highways, notably
Highway 21 due to the
lake effect of
Lake Huron
Lake Huron ( ) is one of the five Great Lakes of North America. It is shared on the north and east by the Canadian province of Ontario and on the south and west by the U.S. state of Michigan. The name of the lake is derived from early French ex ...
, which can result in sudden
snowsquall
A snow squall, or snowsquall, is a sudden moderately heavy snowfall with blowing snow and strong, gusty surface winds. It is often referred to as a whiteout and is similar to a blizzard but is localized in time or in location and snow accumula ...
conditions during the winter.
History
Halton was the first jurisdiction in Ontario to create EDRs, although it initially referred to them as ''Emergency Diversion Routes''. In August 1999, the regional council approved the preparation of the ''Road Closure Action Plan'' (RCAP), which was developed with input from the
Halton Regional Police Services
The Halton Regional Police Service provides policing service for the Regional Municipality of Halton, which is located southwest of Toronto, in Ontario, Canada. Halton Region encompasses the city of Burlington and the Towns of Oakville, Milton ...
and the
Ministry of Transportation of Ontario
The Ministry of Transportation (MTO) is the provincial ministry of the Government of Ontario that is responsible for transport infrastructure and related law in Ontario, Canada. The ministry traces its roots back over a century to the 1890s, w ...
(MTO).
The RCAP utilized folding signs that police could open to "activate" the route. Similar in appearance to the EDR signs of today, the RCAP signs featured a trapezoid shaped orange EDR sign, as opposed to an orange square with a black circle containing the letters EDR. These signs were first deployed along a limited stretch of the
Queen Elizabeth Way
The Queen Elizabeth Way (QEW) is a 400-series highways, 400-series highway in the Canadian province of Ontario linking Toronto with the Niagara Peninsula and Buffalo, New York. The highway begins at the Canada–United States border on the Pea ...
in March 2001,
between Dorval Drive and Trafalgar Road in
Oakville and between Bronte Road and Burloak Drive in
Burlington, both the location of major ravines with limited alternative crossings.
By the spring of 2003, when the deployment of the system was complete, the entire Queen Elizabeth Way,
Highway 401
King's Highway 401, commonly referred to as Highway 401 and also known by its official name as the Macdonald–Cartier Freeway or colloquially referred to as the four-oh-one, is a controlled-access 400-series highway in the Canadian provi ...
and
Highway 403 had diversion routes within Halton Region.
Following Halton's tests, the MTO and the
Ontario Good Roads Association
Ontario is the southernmost province of Canada. Located in Central Canada, Ontario is the country's most populous province. As of the 2021 Canadian census, it is home to 38.5% of the country's population, and is the second-largest province by ...
formed a joint task force, and using the RCAP as a model, developed the Emergency Detour Route program.
In 2010 and 2011, an aggressive program was instituted to place EDRs alongside major routes throughout the province.
Alberta
Highway 2 uses
Highway 2A as an Emergency Detour Route. On Highway 2, there are signs with flashing lights indicating when to take the next exit to use the detour route.
Germany
Every exit on the German
Autobahn
The (; German , ) is the federal controlled-access highway system in Germany. The official term is (abbreviated ''BAB''), which translates as 'federal motorway'. The literal meaning of the word is 'Federal Auto(mobile) Track'.
Much of t ...
and some other
expressways
Expressway may refer to:
*Controlled-access highway, the highest-grade type of highway with access ramps, lane markings, etc., for high-speed traffic
*Limited-access road, a lower grade of highway or arterial road
* ''Expressway'' (film), a 2016 Fi ...
has a pre-posted "on-demand" detour route ''(
German
German(s) may refer to:
* Germany, the country of the Germans and German things
**Germania (Roman era)
* Germans, citizens of Germany, people of German ancestry, or native speakers of the German language
** For citizenship in Germany, see also Ge ...
: Bedarfsumleitung)'' marked with a blue and white sign having a number starting with a "U" (short for "Umleitung", German for "detour".) In the event an Autobahn segment must be closed due to a crash, road work, or other incident, drivers can be diverted off the Autobahn to follow the numbered signs over the adjacent secondary road network to the next downstream Autobahn entrance. In the event that entrance is also closed, signs will indicate to motorists to follow the next sequentially-numbered route. Odd-numbered detour routes are used for northbound and eastbound travel, while even-numbered routes are used for southbound and westbound travel. The detours can also optionally be used to circumnavigate traffic jams.
As the detours use secondary roadways, federal administrative rules require consultation with local authorities when planning the detour routes, and routes are selected to minimize distance, stops (i.e. traffic signals), and disruption to nearby communities as much as possible.
Ireland
Following the identification of emergency diversion routes on the
M50 in 2016, a set of symbols to indicate such routes was introduced. The operation of these routes as well as the symbols used are similar to that in the UK, although hollow shape symbols are not used. They are typically displayed on directional signs, or are displayed on their own signs with an arrow indicating the direction of the route. In the event of a road closure, a
variable message sign
A variable- (also changeable-, electronic-, or dynamic-) message sign or message board, often abbreviated VMS, VMB, CMS, or DMS, and in the UK known as a matrix sign,
is an electronic traffic sign often used on roadways to give travelers info ...
will display a message indicating the symbol to be followed, allowing drivers to bypass the closure.
Sweden
Sweden
Sweden, formally the Kingdom of Sweden, is a Nordic countries, Nordic country located on the Scandinavian Peninsula in Northern Europe. It borders Norway to the west and north, and Finland to the east. At , Sweden is the largest Nordic count ...
use signs with white background and blue text for their permanent detour routes ''(
Swedish
Swedish or ' may refer to:
Anything from or related to Sweden, a country in Northern Europe. Or, specifically:
* Swedish language, a North Germanic language spoken primarily in Sweden and Finland
** Swedish alphabet, the official alphabet used by ...
: permanent omledningsväg)'' on numbered roads. According to
the Swedish Transport Administration's guidelines a permanent detour route should be able to handle all the traffic when it comes to
capacity
Capacity or capacities may refer to:
Mathematics, science, and engineering
* Capacity of a container, closely related to the volume of the container
* Capacity of a set, in Euclidean space, the total charge a set can hold while maintaining a giv ...
, weight, height, etc. as sorting traffic is almost impossible. In cases that for some reason need traffic sorting the
police
The police are Law enforcement organization, a constituted body of Law enforcement officer, people empowered by a State (polity), state with the aim of Law enforcement, enforcing the law and protecting the Public order policing, public order ...
will
regulate
Regulate may refer to:
* Regulation
Regulation is the management of complex systems according to a set of rules and trends. In systems theory, these types of rules exist in various fields of biology and society, but the term has slightly diff ...
the traffic. However, there may be different routes for different travel directions as to not create accessibility problems or queues due to limited capacity; in these cases a letter for the
cardinal direction
The four cardinal directions or cardinal points are the four main compass directions: north (N), south (S), east (E), and west (W). The corresponding azimuths ( clockwise horizontal angle from north) are 0°, 90°, 180°, and 270°.
The ...
is added at the end. The guidelines also emphasize that the segments of the permanent detour route should be as short as possible with access to the main route whenever it is possible.
United Kingdom
The
United Kingdom
The United Kingdom of Great Britain and Northern Ireland, commonly known as the United Kingdom (UK) or Britain, is a country in Northwestern Europe, off the coast of European mainland, the continental mainland. It comprises England, Scotlan ...
use yellow signs with a series of symbols for their emergency diversion routes. Symbols come in a shapes, with a solid and hollow version, including circle, triangle, square and diamond. When a roadway is closed, a trigger sign is opened at the last junction prior to the closure, displaying a symbol, which motorists can follow to rejoin the route at a point beyond the closure.
United States
The federal
Manual on Uniform Traffic Control Devices
The ''Manual on Uniform Traffic Control Devices for Streets and Highways'' (usually referred to as the ''Manual on Uniform Traffic Control Devices'', abbreviated MUTCD) is a document issued by the Federal Highway Administration (FHWA) of the Unit ...
introduced signage for these routes in its eleventh edition in December 2023.
Michigan
Michigan
Michigan ( ) is a peninsular U.S. state, state in the Great Lakes region, Great Lakes region of the Upper Midwest, Upper Midwestern United States. It shares water and land boundaries with Minnesota to the northwest, Wisconsin to the west, ...
has a system of
special route
In road transportation in the United States, a special route is a road in a numbered highway system that diverts a specific segment of related traffic away from another road. They are featured in many highway systems; most are found in the Inte ...
s called "Emergency" routes which parallel major highways, primarily in Southwestern Michigan. These routes provide relief in the event of emergency closures to a
freeway
A controlled-access highway is a type of highway that has been designed for high-speed vehicular traffic, with all traffic flow—ingress and egress—regulated. Common English terms are freeway, motorway, and expressway. Other similar terms ...
due to accidents, weather, or other civil emergencies. Emergency routes have been gradually put in place as part of a broader plan by the
Michigan Department of Transportation
The Michigan Department of Transportation (MDOT) is a constitutional government principal department of the US state of Michigan. The primary purpose of MDOT is to maintain the Michigan State Trunkline Highway System which includes all Interst ...
(MDOT) to upgrade its
ITS
ITS, its or it's may refer to:
Language
* It's, an English contraction of ''it is'' or ''it has''
* Its (pronoun), the possessive form of the pronoun it
* Itsekiri language (ISO 639 language code its), a language found in Nigeria and the Niger De ...
network across the state. These detours may or may not follow MDOT-maintained
State Highways
A state highway, state road, or state route (and the equivalent provincial highway, provincial road, or provincial route) is usually a road that is either Route number, numbered or maintained by a sub-national state or province. A road numbered ...
, however, and some portions of the routes pass through urban or suburban areas.
Emergency routes exist on and parallel to
Interstate 69 (I-69) and
I-94[ and US Highway 31 (US 31).
These routes are signed with an auxiliary "Emergency" plate that is colored orange, indicating a temporary traffic control sign.
Emergency US 31, which offers an alternative crossing of the Grand River in the event that the ]bascule bridge
A bascule bridge (also referred to as a drawbridge or a lifting bridge) is a moveable bridge with a counterweight that continuously balances a span, or leaf, throughout its upward swing to provide clearance for boat traffic. It may be single- o ...
in Grand Haven
Grand Haven is a city within the U.S. state of Michigan and the county seat of Ottawa County. Grand Haven is located on the eastern shore of Lake Michigan at the mouth of the Grand River, for which it is named. As of the 2020 census, Grand Ha ...
, Michigan
Michigan ( ) is a peninsular U.S. state, state in the Great Lakes region, Great Lakes region of the Upper Midwest, Upper Midwestern United States. It shares water and land boundaries with Minnesota to the northwest, Wisconsin to the west, ...
is unavailable for motorists, is one such route. According to MDOT, "this route would only be used in emergency situations and worst-case scenarios impacting the entire bridge structure."
Missouri
Missouri
Missouri (''see #Etymology and pronunciation, pronunciation'') is a U.S. state, state in the Midwestern United States, Midwestern region of the United States. Ranking List of U.S. states and territories by area, 21st in land area, it border ...
uses "Incident By-Pass Routes" along its highways.
Nebraska
Nebraska
Nebraska ( ) is a landlocked U.S. state, state in the Midwestern United States, Midwestern region of the United States. It borders South Dakota to the north; Iowa to the east and Missouri to the southeast, both across the Missouri River; Ka ...
has created an alternate route for Interstate 80
Interstate 80 (I-80) is an east–west transcontinental freeway that crosses the United States from San Francisco, California, to Teaneck, New Jersey, in the New York metropolitan area. The highway was designated in 1956 as one of the ori ...
.
New York
The New York State Thruway
The New York State Thruway (officially the Governor Thomas E. Dewey Thruway and colloquially "the Thruway") is a system of controlled-access toll roads spanning within the U.S. state of New York. It is operated by the New York State Thruway ...
uses emergency detour signs to divert traffic from the Thruway in the event of weather conditions or other emergencies.
Ohio
Ohio
Ohio ( ) is a U.S. state, state in the Midwestern United States, Midwestern region of the United States. It borders Lake Erie to the north, Pennsylvania to the east, West Virginia to the southeast, Kentucky to the southwest, Indiana to the ...
has established a permanent detour scenario of Interstate 70
Interstate 70 (I-70) is a major east–west Interstate Highway in the United States that runs from Interstate 15, I-15 near Cove Fort, Utah, to Interstate 695 (Maryland), I-695 and Maryland Route 570 (MD 570) in Woodlawn, Baltimo ...
east of Columbus, due to frequent flooding.
Alternate Interstate routes also exist for I-70 near Dayton as well as for Interstate 76
Interstate 76 or I-76 may refer to:
Transportation
* Interstate 76 (Colorado–Nebraska) (I-76), US
* Interstate 76 (Ohio–New Jersey) (I-76), running through Pennsylvania, US
Other uses
* ''Interstate '76'', a vehicular combat video game for W ...
and Interstate 77
Interstate 77 (I-77) is a north–south Interstate Highway in the Eastern United States. It traverses diverse terrain, from the mountainous state of West Virginia to the rolling farmlands of North Carolina and Ohio. It largely supplants the ...
in Summit County.
Pennsylvania
Pennsylvania
Pennsylvania, officially the Commonwealth of Pennsylvania, is a U.S. state, state spanning the Mid-Atlantic (United States), Mid-Atlantic, Northeastern United States, Northeastern, Appalachian, and Great Lakes region, Great Lakes regions o ...
has a system of "color detour signs" in which any detour follows signs with a specific color. The detours are meant to be used if a limited-access highway
A limited-access road, known by various terms worldwide, including limited-access highway, partial controlled-access highway, and expressway, is a highway or arterial road for high-speed traffic which has many or most characteristics of a contro ...
has to be closed for an emergency situation such as a flood
A flood is an overflow of water (list of non-water floods, or rarely other fluids) that submerges land that is usually dry. In the sense of "flowing water", the word may also be applied to the inflow of the tide. Floods are of significant con ...
or car accident
A traffic collision, also known as a motor vehicle collision, or car crash, occurs when a vehicle collides with another vehicle, pedestrian, animal, road debris, or other moving or stationary obstruction, such as a tree, pole or building. T ...
, directing motorists along local roads near the limited-access highway to the next exit. According to a document produced by the Delaware Valley Regional Planning Commission
The Delaware Valley Regional Planning Commission (DVRPC) is the metropolitan planning organization for the Delaware Valley. Created in 1965 by an interstate compact, DVRPC is responsible for transportation and regional planning in the greater Phi ...
containing information from the Pennsylvania Department of Transportation
The Pennsylvania Department of Transportation (PennDOT) oversees transportation issues in the Pennsylvania, Commonwealth of Pennsylvania. The administrator of PennDOT is the Pennsylvania Secretary of Transportation, Michael B. Carroll. PennDOT ...
, they are generally color-coded according to direction, with blue meaning north, red meaning south, green meaning east, and orange meaning west, with other colors sometimes being used when detour routes overlap with one another.[ However, the Pennsylvania Department of Transportation's own sign manual recommends that only black, blue, or orange be used.
]
West Virginia
The West Virginia Turnpike
Interstate 77 (I-77) in the US state of West Virginia is a major north–south Interstate Highway. It extends for between Bluefield, West Virginia, Bluefield at the Virginia state line and Williamstown, West Virginia, Williamstown at the ...
has a series of lettered detours, first posted in early 2012, along its route.
Wisconsin
Wisconsin
Wisconsin ( ) is a U.S. state, state in the Great Lakes region, Great Lakes region of the Upper Midwest of the United States. It borders Minnesota to the west, Iowa to the southwest, Illinois to the south, Lake Michigan to the east, Michig ...
has "alternate route designations" on local surface roads and streets for all five primary interstate highways and three auxiliary interstates, along with several U.S. highways and state trunk highways.
Notes
References
External links
*{{commonscat-inline, Permanently signed detour routes
Road transport