A frontage road (also access road, feeder, service drive, service road, outer road, and especially surface road) is a non-limited access road running parallel to a higher-speed road, usually a freeway, and feeding it at appropriate points of access (interchanges). In many cases, the frontage road is a former highway already in existence when the limited access road was built. In other cases they may be built prior to construction of the highway. In urban areas, frontage roads are frequently one way roads when they exist on both sides of a highway. In more rural ones, roads are typically two-way.
Frontage roads provide access to homes and businesses which would be cut off by a limited access road and connect these locations with roads which have direct access to the main roadway. Frontage roads give indirect access to abutting property along a freeway, either preventing the commercial disruption of an urban area that the freeway traverses or allowing commercial development of abutting property. At times, they add to the cost of building an expressway due to costs of land acquisition and the costs of paving and maintenance. However, the benefits of nearby real estate can more than offset the cost of building the frontage roads. Furthermore, a frontage road may be a part of an older highway, so the expense of building a frontage road may be slight. Conversely, the existence of a frontage road can increase traffic on the main road and be a catalyst for development; hence there is sometimes an explicit decision made to not build a frontage road.
A backage road is a similar concept, but lies on the other side of the land parcels that abut the frontage road. It serves mainly to provide access to those parcels without using the frontage road.
Most Texas freeways have frontage roads on both sides. In urban and suburban areas, the traffic typically travels one-way only in the direction of the neighboring main lanes. Most other areas have two-way traffic, but as an area urbanizes the highway is often transformed for one-way traffic. Over 80% of Houston freeways have frontage roads , which locals typically call feeders. Many frontage roads in urban and suburban areas of Texas have the convenience of Texas U-turns, which allow drivers to avoid being stopped by traffic lights when making a U-turn.
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 until then of slight value 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 did not need to acquire and demolish developed property; in return the developer profited handsomely from lucrative development along the freeway.
With the arguable exception of Missouri, Texas is the only state in the USA that widely constructs frontage/access roads along its highways state-wide, even in some rural areas. Outside of these two states, frontage roads are common in Arizona, Florida, Georgia, Louisiana, Michigan, Mississippi, New Mexico, and Nevada, and then only in urban or suburban areas.
Frontage roads are often built as part of a multi-phase plan to construct new limited access highways. Therefore, they initially serve as a highway with access to local business before the freeway is constructed several years later. Even after the completion of the new freeway, frontage roads serve as a major thoroughfare for local activity, such as with the Katy Freeway project in Greater Houston In several cases, a long range plan has called for a future freeway, but the design is either changed or the project cancelled before completion
Entering and exiting from access roads can be very confusing to drivers unfamiliar with the system. Signaling is very important not just for the drivers behind one, but also for oncoming traffic in areas where the access road is two-way.
Nicknames for frontage roads vary within the state of Texas. In Houston and East Texas they are called feeders. Dallas and Fort Worth residents call their frontage roads "service roads". El Paso residents call their frontage roads "gateways". In Austin and San Antonio, however, they use the state's official term of "frontage roads" and also "access 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
Michigan left hand turns 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.
There are no other Michigan frontage roads running more than one mile in length outside of the Metro Detroit area. 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.
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/de-acceleration 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.
List of Service Roads on the QEW:
List of Service Roads on the 403:
List of RIRO on the 427: