Slip ramp

A frontage road (also known as an access road, service road, parallel road, etc.) is a local road running parallel to a higher-speed, limited-access road. A frontage road is often used to provide access to private driveways, shops, houses, industries or farms. Where parallel high-speed roads are provided as part of a major highway, these are also known as local-express lanes.

A frontage lane is a paved path that is used for the transportation and travel from one street to another. 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.

Frontage roads provide access to homes and businesses which would otherwise 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 and the costs of paving and maintenance.

However, the benefits of development 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. And finally, the cost to purchase access rights from adjacent property may exceed the costs to build frontage roads. 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 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.

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Wikipedia