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[[File:Frontage Road Interchange.png|thumb|Illustration of a Frontage Road Interchange. Traffic is permitted to move only in the direction indicated by the arrows. ]]
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.
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.
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 street 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.
The outer lanes may also be known as a collector/distributor road where slip road 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.
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.
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.
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 arterial road.
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:
List of service roads on ON-400:
List of service roads on ON-403:
List of RIRO intersections on ON-427:
The South Luzon Expressway (SLEX) has two two-way service roads running alongside the road within Metro Manila. Philippine National Railways (PNR) tracks and a section of the Metro Manila Skyway around Ninoy Aquino International Airport run between the expressway and its East Service Road between Nichols station and Bicutan station. The service roads begin at Sales Interchange at Pasay up until Alabang exit in Muntinlupa.
Outside the expressways, some of the wider major roads in Metro Manila feature service roads for business access. Roxas Boulevard features a service road to the east, running from Kalaw Avenue in Ermita, Manila to C. Rivera Street in Pasay. Ortigas Avenue in Greenhills, San Juan contains two one-way service roads, the eastbound one serving businesses at the avenue's south side, and the westbound one carrying local traffic at Greenhills. Quezon Avenue in Quezon City runs an eastbound one-way service road from Timog Avenue and East Avenue which crosses EDSA. Outside Metro Manila, service roads are implemented on some urban segment of major national roads such Maharlika Highway (Route 1) in Tagum, Davao del Norte and Benigno S. Aquino Jr. Avenue (Routes 5 and 512) in Iloilo City.
Though Alaska has very few roads that are built to freeway standard, a couple of the highways that are do have frontage roads; notably along the Seward Highway (Alaska Route 1) with Homer Drive running south (from Tudor Road to Dimond Boulevard) and Brayton Drive running north (from DeArmoun Road to Tudor Road); and the Minnesota Drive Expressway (from West 100th Ave to Dimond Boulevard) in South Anchorage. Also, the George Parks Highway (Alaska Route 3) has two-way street frontage roads running along it from the Trunk Road exit to the Seward Meridian Parkway exit (Fireweed Road on the south side and Blue Lupine Drive on the north side) in Wasilla.
In metropolitan Phoenix, the state's first freeway, Interstate 17 has a frontage road (Black Canyon Highway); some sections of the frontage road was reduced to a single lane in the 1990s when I-17 was widened. Several freeways overbuilt existing arterials, which were converted to frontage roads: Price Road (Tempe), Pima Road (Scottsdale) and Beardsley Road (north Phoenix) on the Loop 101, as well as 59th Avenue on the Loop 202 Ed Pastor (South Mountain) Freeway. In Tucson, I-10 has a two-lane, one-way frontage road, and in between Casa Grande and Tucson, a two-lane, two-way street frontage road.
Interstate 210 in California near Pasadena and Arcadia has frontage roads which include Corson Street in Pasadena (parallel to I-210 West) and Maple Street (parallel to I-210 East) in Pasadena, while Central Avenue (parallel to I-210 West) and Evergreen Avenue (parallel to I-210 East) are in Arcadia.
In Orange County, frontage roads exist on sections of these four highways:
Typical service roads also exist along the eight-lane freeway section of Massachusetts Route 2 through Arlington and Belmont (two near northwestern suburbs of Boston) and United States Route 1 in Lynnfield.
In Fall River, from 1965 to 2023, Davol Street served as the frontage road for Massachusetts Route 79 between "Broadway Extended", Anawan and Pocasset Streets, Central Street, and Interstate 195 in the south, to Brightman Street in the north. For most of this stretch, Davol Street is split, with the Western Fall River Expressway (Route 79) running between a one-way pair of northbound North Davol Street and southbound South Davol Street. Until its closure in 2011, the Brightman Street Bridge carried U.S. Route 6 and Route 138 between Somerset and Fall River. At the eastern approach to the bridge, US 6 and MA 138 connected to MA 79, Brightman Street, and both sides of Davol Street at a complex interchange (to and from MA 79)/intersection (to and from US 6/MA 138, Brightman Street, and both sides of Davol Street). North of this interchange/intersection, both sides of Davol Street become the exit ramp from MA 79 southbound and entrance ramp to MA 79 northbound.
After the Veterans Memorial Bridge replaced the Brightman Street Bridge in 2011, this relocated US 6 and MA 138 onto a taller, expressway-like bridge with a large modified trumpet-style interchange with MA 79 and both sides of Davol Street. A new U-turn ramp from North Davol Street to South Davol Street and MA 79 southbound was added, along with a bike path along the bridge from Somerset and then south to Brightman Street. Brightman Street itself could only be accessed from North Davol Street; traffic from Brightman Street had to use local side streets to reach North Davol Street to access either direction of MA 79, US 6, and MA 138.
In 2015 and 2016, the Fall River Viaduct carrying MA 79 to its terminus at MA 138 and I-195 was demolished. When reconstruction was complete in 2016, Routes 79 and 138 were merged onto one boulevard-style Davol Street roadway with signaled intersections (at Central Street, Anawan and Pocasset Streets, and a new complex intersection with connections to I-195, Millikan Boulevard, and Ponta Delgada Boulevard/Water Street) from a partially-reconstructed partial interchange just south of Brownell Street.
By spring 2023, the Massachusetts Department of Transportation (MassDOT) had closed and started to remove some of the Route 79 expressway between the partial interchange from just south of Brownell Street at the southern end and the Veterans Memorial Bridge interchange at the northern end. All Route 79 traffic has been directed onto both sides of the Davol Street frontage road south of the Veterans Memorial Bridge interchange. Part of the 2011 Veterans Memorial Bridge interchange was closed or modified as well, most notably the ramp from US 6 eastbound/MA 138 southbound on the bridge to MA 79 southbound and the aforementioned U-turn ramp from North Davol Street to South Davol Street and Route 79 southbound (a temporary U-turn to the south has been built in its place for use during the construction period).
During re-construction of Davol Street as a boulevard, a temporary roadway will be built at-grade on the site of the former elevated expressway, with all traffic using it until the reconstructed halves of Davol Street are finished. Afterwards, the temporary roadway will be removed, with the land being slated for redevelopment, and all Route 79/138 traffic will return to North and South Davol Streets. By the completion of the project, the removal of the expressway will eliminate the frontage road status of North and South Davol Streets.
North and South Davol Streets carry US 6 from the Veterans Memorial Bridge (and before that, the Brightman Street Bridge) to President Avenue, where it turns east to cut through the city.
Between the mid-1960s and 2023, the status of Route 138 between "Broadway Extended" and either bridge to Somerset has been up for debate. Signs dating back to, and possibly prior to, the construction of the Fall River Viaduct (demolished 2015-2016) indicate that this stretch of Davol Street carries Route 138. Most signs from the mid-1960s indicate that MA 138 joins Route 79 from its southern end and leaves it at the ramps to either bridge to Somerset. However, some signs along President Avenue (US 6) and South Davol Street (and formerly also near the pre-2015 site of the split of Davol Street into the one-way pair) indicated that Route 138 still used the one-way pair of North and South Davol Streets. The elimination of the Route 79 expressway largely will end this decades-long debate, as North and South Davol Streets will carry all traffic (US 6 and Routes 79 and 138) from Central Street in the south to the Veterans Memorial Bridge in the north, where the Davol Street halves will re-join and serve as the transition to a new, permanent "southern end" of the truncated Western Fall River Expressway.
Michigan Left are also quite common at surface street-frontage road intersections, with dedicated turnaround lanes (similar to the Texas U-turn) built over the freeway on separate bridges approximately 100 meters from the main intersection and bridging.
With the exceptions of Interstate 275 and the freeway portion of M-53, every Metro Detroit freeway has a frontage road along it for at least a portion of its length. Several other freeways outside Metro Detroit use these as well.
There are two other cities in Michigan where frontage roads running more than one mile in length outside of Metro Detroit can be found. There are frontage roads along Interstate 496 and U.S. Route 127 in Greater Lansing and along Interstate 475 in Downtown Flint. Outside the cities, US-23 has them from Ann Arbor to Fenton, while US-127 has them from Leslie to Mason. New freeway construction in Michigan has not included frontage roads since the completion of Interstate 696, most of which was constructed along the rights of way of major surface arteries, in 1989. Michigan does not build frontage roads in rural areas.
Some former sections of US 10 in the west (Saint Regis to Butte along Interstate 90) and east (Billings to North Dakota along Interstate 94) also serve as frontage roads.
Upstate, frontage roads are less common. New York State Route 104 has frontage roads along its limited access portions in Irondequoit and Webster, and the Southern Tier Expressway (I-86) in Horseheads has two short frontage roads (Brickyard Lane and Fairport Lane) during its Elevated highway portion. These stretches of service roads have signalized intersections with main roadways, as well as RIRO-style intersections with tertiary roadways and larger commercial properties.
Most Texas have service roads on both sides. In urban and suburban areas, the traffic typically travels one-way, in the direction of the adjacent freeway. Most other areas have two-way street, but as an area urbanizes, the frontage road is often converted to one-way traffic (2 lanes). In cases of freeway congestion or shutdown, the frontage road provides an instant detour, subject to delays at each stop sign or stoplight at cross streets.
Where two new Texas freeways meet, especially on the edge of major metropolitan areas, the state will often first build the junctions for the one-way frontage roads—that is, four at-grade intersections—followed by an overpass where one freeway crosses over another. This requires motorists who desire to switch freeways to exit to the adjacent frontage road, turn at an at-grade intersection onto the frontage road for the other freeway, and then merge into the other freeway. As traffic increases at the at-grade intersections, the state slowly adds direct ramps between freeways for the most in-demand traffic movements, thereby reducing such inconvenience for motorists.
Over 80% of Houston freeways have service roads, "CH2 freeway metropolis pp 92–115 72" (PDF). houstonfreeways.com which locals typically call feeders. Many service roads in urban and suburban areas of Texas have the convenience of , as a left lane curving under an overpass, allowing drivers to avoid stopping for traffic lights when making a U-turn.
Service roads are often built as part of a multi-phase plan to construct new limited-access highways. They initially serve as a highway with access to local business before the freeway is constructed years later. After the completion of the freeway, frontage roads serve as a major thoroughfare for local activity, such as with the Katy Freeway project (I-10) in Greater Houston. In several cases, a long-range plan has called for a future freeway, but the design has either changed or the project was canceled before completion. "Houston cancelled". texasfreeway.com.
Nicknames for frontage roads vary within the state of Texas. In Houston and East Texas, they are called feeders. Dallas and Fort Worth area residents call their frontage roads "service roads", and "access roads" is the predominant term used in San Antonio. Dialect Survey Maps , map #99 Most signs reference "Frontage Road" despite local regional vernacular (there are signs in Houston that use the term "feeder").
In Houston, the free sections of Beltway 8, SH 249 and FM 1093, not part of the Sam Houston Tollway, Tomball Tollway, and Fort Bend Westpark Tollway (respectively) are composed of frontage roads.
In 2002, the Texas Department of Transportation proposed to discontinue building frontage roads on new freeways, citing studies that suggest frontage roads increase congestion. However, this proposal was widely ridiculed and criticized and was dropped later the same year. Backing Out of Frontage Roads? window.state.tx.us
The Stemmons Freeway in Dallas illustrates the practicability of the frontage road: the real estate developer John Stemmons offered free land to the Texas Highway commission in which to build a freeway (Interstate 35E) on the condition that the state build the freeway with frontage roads that would give access to undeveloped property that he owned along the freeway corridor. The state was able to reduce its costs (largely the cost of land acquisition) of building the freeway, and didn't need to acquire and demolish developed property; the developer profited from development along the freeway. San Antonio developer Charles Martin Wender used the same tactic for his Westover Hills development, offering free land through the middle of his property for SH 151 as well as paying half the costs for the initial frontage road construction. Following Wender's lead, several neighboring landowners also donated right-of-way for the route.
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