A frontage road (also known as an access road, outer road, service road, feeder road, or parallel road) is a local road running parallel to a higher-speed, limited-access road. Where parallel high-speed roads are provided as part of a major highway, these are also known as local lanes. Sometimes a similar arrangement is used for city roads; for example, the collector portion of Commonwealth Avenue in Boston, U.S., is known as a carriage road.
A frontage road is often used to provide access to private driveways, shops, houses, industries or farms that would otherwise be cut off by a limited-access road. This can prevent the commercial disruption of an urban area that the freeway traverses or allow commercial development of bordering property.
Advantages
There are several advantages to using frontage roads. One advantage is to separate local traffic from through traffic. When frontage roads are lacking in an urban area, the highway is used as a local road, reducing speeds and increasing congestion. Another advantage is to provide an alternative when the highway is closed or obstructed.
The existence of a frontage road can also be a catalyst for development, and property values along the highway often increase after the construction of frontage roads.
Disadvantages
There are also some disadvantages to using frontage roads. When frontage roads are used without controlling the access to the primary road, at every intersection where an intersecting road runs across the primary, the number of conflict points increases one fold for each frontage road, since each frontage road is itself another intersection. A highway with frontage roads can be difficult for pedestrians to cross, for a variety of reasons including, but not limited to when neither the primary road nor the crossing is elevated, or gaps in traffic are few and the intervals between those gaps is long. Such examples include:
US 190 in East Baton Rouge Parish, Louisiana; LA 1 in West Baton Rouge Parish, Louisiana; Palatine Road in Cook County, Illinois; The northeast edge of Spur 503 in Denison, Texas; The Southeast edge of U.S. Route 69 in McAlester, Oklahoma.
A complex example is US 77/Commerce () in Ardmore, Oklahoma, particularly at the Grand Avenue intersection. Right turns from the central carriageways are not allowed; a slip ramp must be taken to the two-way frontage road, where the turning traffic must yield to the through traffic. Only then can a vehicle make a right turn from the signal on the frontage road.
Furthermore, frontage roads can increase urban sprawl. Land along highways is made open for development, allowing shopping centers and other buildings to sprawl.
Cost can also be a disadvantage, as building a highway with frontage roads can be more expensive than building a highway alone.
Local–express lane system
A different alternative to the concept of frontage roads in urban freeways is the local–express system, which is designed to handle closely spaced interchange ramps without disrupting through traffic. Unlike frontage roads, the local lanes are typically high-speed fully controlled-access lanes, conforming to freeway requirements. These local lanes will run along the outside of the inner express lanes.
The outer lanes may also be known as a collector/distributor road where slip ramps provide access to and from the inner mainline lanes. This distinction is usually made when the outer lanes are only present by an interchange and not the full length of the highway.
For even more capacity, frontage roads may feed into and from freeway local lanes although this is less common.
Related road types
A frontage lane is a paved path that is used for the transportation and travel from one street to another. The difference is that typically a frontage road will follow along the side of a highway, whereas a frontage lane is a short connection between two different roads. Frontage lanes, closely related to a frontage road, are common in metropolitan areas and in small rural towns. Frontage lanes are technically not classified as roads due to their purpose as a bridge from one road to another, and due to the architectural standards that they are not as wide as a standard road, or used as commonly as a standard road, street, or avenue.
A backage road is a similar concept to a frontage road, but lies on the back side of the land parcels that abut the controlled access's right of way. Like the frontage road, it serves mainly to provide access to those parcels as an alternative to a frontage road. Regardless of which direction the businesses face, the difference is that backage roads will be sandwiched between businesses and be separated from the freeway, whereas frontage roads will be right beside a freeway.
Some make a distinction between frontage roads and parallel roads. Frontage roads may more commonly refer to the one-way roads alongside a freeway, whereas parallel roads more commonly refer to the two-way roads running alongside a freeway.
Examples
Argentina In Argentina, especially around Buenos Aires, frontage roads known as colectoras can be found next to freeways. Examples include Avenida General Paz, Ruta 8, and Ruta 9 coming into Buenos Aires.
Canada
Alberta Service or frontage roads feature in many parts of the highway network in Alberta, and are common along freeway-grade or twinned segments of major provincial highways such as Highways 1, 2 and 16, as well as some sections of major two-lane highways. Frontage roads are implemented along provincial highways as part of new construction, upgrading and twinning projects to ensure businesses or landowners along the highway right-of-way retain access to properties which would have direct access to the highway extinguished otherwise by the province.
In cities such as Edmonton and Calgary, frontage road schemes are implemented along freeways, expressways and some high-speed suburban arterial roads. Within Edmonton, one-way frontage roads run along parts of Whitemud Drive and the upgraded Yellowhead Trail for access to surface streets and businesses, and many arterial roads within the inner suburbs often have frontage roads to provide business and residential access away from faster through traffic. Access is usually through crossing streets, interchanges, or occasionally, ramps or direct connectors. In other urban areas, frontage roads are commonly built along a provincial highway through suburban areas to spur commercial development.
British Columbia Bi-directional frontage roads exist both on the North and South sides of the Highway 1 through Abbotsford.
Ontario
A freeway with a significant remaining network of service roads is the Queen Elizabeth Way (QEW). However, most of the slip ramps between St. Catharines and Mississauga were removed during major reconstruction in the 1970s and 1990s. Service roads are no longer able to directly access the QEW; they have been rerouted to intersections with other major roads which have interchanges with the QEW. Nonetheless, the service roads are positioned too close to the QEW to easily widen the freeway unless all the private properties along the service road are bought out. This would be unlikely in the current political environment.
The only remaining slip ramps connecting to service roads are on the QEW running through St. Catharines. These dangerous low-standard ramps (due to lack of acceleration/deceleration lanes) are due to be replaced in a planned extensive reconstruction of the QEW that is currently underway. Similar service roads and slip ramps exist along Highway 401 through Oshawa, but like through St. Catharines, these are also in the process of being replaced with modern ramps.
Highway 427 had its service roads replaced with a collector-express system in the 1970s. However, it has several RIRO access onramps and offramps to serve residential traffic in addition to its standard parclo interchanges with major arterials.
A short section of Highway 400 has the service roads of Davis Road (southbound) and Wist Road (northbound) from South Canal Bank Road to Canal Road in King Township and Bradford West Gwillimbury. There is a RIRO interchange to the service roads, signed as to Canal Road, to access the farms of the Holland Marsh and the town of Bradford West Gwillimbury.
Although not considered a service road, Lake Shore Boulevard in downtown Toronto has several slip ramps that weave in and out of the parallel Gardiner Expressway, in a similar fashion as a service road.
List of service roads on the QEW:
series of broken sections from Cawthra Road in Mississauga to the Garden City Skyway in St. Catharines
List of service roads on ON-400:
Davis Road (southbound) and Wist Road (northbound), King and Bradford West Gwillimbury
List of service roads on ON-403:
North Service Road at QEW/407 junction to Waterdown Rd, Burlington Service Road at Guelph Line, Burlington
List of RIRO intersections on ON-427:
Gibbs Road onto Northbound 427 Eva Road onto/off Southbound 427 Holiday Drive onto/off Southbound 427 Eringate Drive onto/off Southbound 427 Valhalla Inn Road onto Northbound 427
Quebec Many autoroutes in Greater Montreal (including the A-40, A-520, A-13, A-15 and A-25) maintain networks of frontage roads along at least some of their lengths as they pass through urban/developing areas.
India
In India, frontage roads or Service lanes (sometimes called नल्ला "Nullah" in Hindi) exist on most high density dual carriageway roads and dual carriageway highways. On Access controlled Expressways like the Yamuna Expressway, the frontage roads remain separate from the main carriageway throughout the road's length. Retrofitted and previously non-access controlled roads, such as most National Highways, only have service lanes on stretches where fly-overs (overpasses) are built over junctions or through towns.
Mexico In Guadalajara, the López Mateos, Vallarta and Mariano Otero avenues (the latter in the stretch between López Mateos to Niños Héroes) are two-lane avenues surrounded by two one-way frontage roads. Lázaro Cárdenas Expressway is similar, but with three lanes in both the central road and the frontage roads. Because these frontage roads are considered as part of the avenue itself, the central road is known locally as the "central lanes", whereas the frontage roads are known as "lateral lanes". Turns are always forbidden in the central lanes; drivers wishing to make a turn must leave the central lanes and make the turn from the lateral lanes.
Netherlands Frontage roads are common in the Netherlands and detailed in the Dutch national design manual for bicycle traffic as per pages 121 and 127 where they are referred to as parallel roads. In the Netherlands, engineers have used frontage roads to benefit cyclists as well as automobiles. Because frontage roads only carry local traffic, the speed on these roads is low (their speed limit is 30 km/h), making them an ideal environment for bicyclists. Because the speed and volume is so low, no additional treatments are needed to make a service road a safe bike facility. In the Netherlands, service roads are often linked together with bike paths to help create a comprehensive bicycle route, with the bike path links serving as barriers to through motor traffic. Since service roads serve a dual purpose, they are an inexpensive way to create routes in cycling network, compared to cycletracks or stand-alone bike paths. Extensive amounts of information on frontage roads can be found on Northeastern's webpage.
Mainland China