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Highway Functional Classification Chapter 16. Dr. TALEB M. AL-ROUSAN. Highway Functional Classification. Highways are classified according to their respective functions in terms of the character of the service they are providing.
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Highway Functional ClassificationChapter 16 Dr. TALEB M. AL-ROUSAN
Highway Functional Classification • Highways are classified according to their respective functions in terms of the character of the service they are providing. • Primary Classification: Highways and streets are described as rural or urban roads. • Urban and rural areas have different characteristics (type of land and population density) which significantly influence travel patterns. • Second Level Classification for Urban and rural roads: • Principal arterials (includes freeways) • Minor arterials • Major collectors • Minor collectors • Local roads and streets.
Functional System of Urban Roads • Urban roads: all highway facilities within urban areas. • Urban areas: designated by state and local officials, have population of (5000) or more. • Urban areas divided into: • Urbanized areas (population > 50,000) • Small urban areas (population 5000 – 50,000) • Urban roads are functionally classified into: principal arterials, minor arterials, collectors, and locals. • See Figure 16.1 for functional classes of suburban roads.
Urban Principal Arterial System • Serves the major activity center of the urban area. • Consists of the highest-traffic volume corridors. • Carries most trips with origin or destination within urban area. • Serves trips by passing the CBD. • All controlled-access facilities are within this system. • Further divisions (subclasses) based on the type of access to the facility: • Interstate, with fully controlled access and grade separation interchanges. • Expressways, have controlled access but may include at-grade intersections. • Other principal arterials, with partial or no controlled access.
Urban Minor Arterial System • Streets and highways that interconnect with the urban primary arterials. • Serves trips of moderate length. • Places more emphasis on land access than primary arterial. • Might serve local bus routes and connect communities but do not go through neighborhoods. • Spacing is usually not less than 1 mile.
Urban Collector & Local Street System • Collector main purpose: collect traffic from local streets in the residential areas or in CBDs and convey it to the arterial system. • Local streets: all other streets within the urban area that are not included in the other three systems. • Local streets main purpose: to provide access to adjacent land and to the collector streets. • Through traffic is deliberately discouraged on local streets.
Functional System of Rural Roads • Rural roads are the highway facilities outside urban areas. • Rural roads are categorized as: principal arterials, minor arterials, major collectors, minor collectors, and locals. • See Figure 16.2 for functional classes of rural roads.
Rural Principal Arterial System • Consists of network of highways that serve most of interstate trips and part of intrastate trips. • Most of highway trips between urbanized areas and small urban areas are made on this system. • Subclasses: • Freeways: divided highways with full controlled access and no at-grade intersections. • Other principal arterials: all principal arterials not classified as freeways.
Rural Minor Arterial System • Augments the arterial system in the formation of a network of roads that connect cities, large towns, and other traffic generators (resorts). • Travel speeds are high as on the principal arterial system.
Rural Collector System • Carry traffic within individual counties • Trip distances are shorter than those on arterials. • Major collectors: carry traffic to and from county seats and large cities that not directly served by the arterial system. • Minor collectors: collect traffic from local roads and convey it to other facilities.
Rural Local Road System • All roads within the rural area not classified with the other systems. • Serves trips of relatively short distances • Connects adjacent lands with the collector roads.
Other Types of Roads • According to jurisdictional responsibilities (public works, municipalities). • Freeways • Main roads • Secondary roads • Collector roads • Local roads • Belt or ring roads • Radial roads (passes through city center)
Types of Lanes • Climbing lanes • Escaping lane • Acceleration lanes • Deceleration lanes • Turning (storage) lanes • Parking (stopping) lanes • Bus lanes • Bicyclist lanes • Overtaking lanes