أنواع التضاريس والموقع
103 TERRAIN & LOCALE
103.1 General
Many rural design features are significantly
influenced by the topography of the land through which the roadway is
constructed. To characterize variations, Ohio topography is categorized into
three types of terrain: level, rolling or hilly. Locale is used to describe the
type of area and generally refers to the character and extent of development in
the vicinity. Urban, rural, residential, and commercial/industrial are characteristics
often used to describe locale.
103.2 Terrain Types
Level مستوي - Any combination of grades and horizontal and vertical alignment
permitting heavy vehicles to maintain approximately the same speed as passenger
cars. This generally includes grades of no more than 2 percent for a distance
of no more than 2 miles.
Rolling هضبي - Any combination of grades and horizontal and vertical alignment
causing heavy vehicles to reduce their speeds substantially below those of
passenger cars, but not causing heavy vehicles to operate at crawl speeds.
Hilly جبلي - Any combination of grades and horizontal and vertical alignment
causing heavy vehicles to operate at crawl speeds. Hilly terrain in Ohio
conforms to mountainous terrain used in the American Association of State
Highway Transportation Officials (AASHTO) publications.
For design purposes a heavy vehicle is defined as a vehicle with a
mass/power ratio of approximately 200 lb/hp. This represents a typical
semi-truck. Crawl speed is the maximum sustained speed that a heavy vehicle can
maintain on an extended upgrade and varies with the weight of the vehicle and
the steepness of the grade.