United States Freeways

Interstate 80 (Eastshore Freeway) in Berkeley, a typical American freeway

In the United States of America, a freeway is a divided highway with full control of access. This means two things. First, adjoining property owners do not have a legal right of access, meaning that they cannot connect their lands to the highway by constructing driveways. When an existing road is converted into a freeway, all existing driveways must be removed and access to adjacent private lands must be blocked with fences or walls. Second, traffic on the highway is “free-flowing”, although many non-engineers misapprehend the “free” in “freeway” to mean that such a highway must be free of charge to use. All cross-traffic (and left-turning traffic) has been relegated to overpasses or underpasses, so that there are no traffic conflicts on the main line of the highway which must be regulated by a traffic light, stop signs, or other traffic control devices. Achieving such free flow requires the construction of many bridges, tunnels, and ramp systems. The advantage of grade-separated interchanges is that freeway drivers can almost always maintain their speed at junctions since they do not need to yield to crossing traffic.