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Minimum lane width: The minimum lane width is 12 feet (3.7 m), identical to most US and state highways. Shoulder width: The minimum width of the left paved shoulder is 4 feet (1.2 m), and of the right paved shoulder 10 feet (3.0 m). With three or more lanes in each direction, both shoulders are to be at least 10 feet (3.0 m) wide.
A size chart illustrating the ANSI sizes. In 1992, the American National Standards Institute adopted ANSI/ASME Y14.1 Decimal Inch Drawing Sheet Size and Format, [1] which defined a regular series of paper sizes based upon the de facto standard 8 + 1 ⁄ 2 in × 11 in "letter" size to which it assigned the designation "ANSI A".
The selection of lane width affects the safety, maximum capacity, and cost, of a highway. Safety is best at a width of 3.0 to 3.1 metres (9.8 to 10.2 ft) in urban settings, where both narrow (less than 2.8 metres (9 ft 2 in)) and wide (over 3.1 metres (10 ft)) lanes have higher crash risks.
In civil engineering, clearance refers to the difference between the loading gauge and the structure gauge in the case of railroad cars or trams, or the difference between the size of any vehicle and the width/height of doors, the width/height of an overpass or the diameter of a tunnel as well as the air draft under a bridge, the width of a lock or diameter of a tunnel in the case of watercraft.
In the United States, the Interstate Highway standards for the Interstate Highway System use a 12 ft (3.7 m) standard lane width, while narrower lanes are used on lower classification roads. In Europe, laws and road widths vary by country; the minimum widths of lanes are generally between 2.5 to 3.25 m (8.2 to 10.7 ft). [ 13 ]
The DMRB is used to design trunk roads such as the A20 in the UK. The Design Manual for Roads and Bridges (DMRB) is a series of 15 volumes that provide standards, advice notes and other documents relating to the design, assessment and operation of trunk roads, including motorways in the United Kingdom, and, with some amendments, the Republic of Ireland.
In UK, the "standard minimum clearance" for structures over public highways is 16 feet 6 inches (5.03 m). [3] In United States, the "minimum vertical clearance" of overpasses on Interstate Highway System is 16 feet (4.9 m).
A route shield pavement marking measures approximately 6 by 15 feet (1.8 m × 4.6 m). It is half the width of a standard Interstate highway lane; like some other kinds of pavement markings, it is elongated to appear proportional to a driver traveling at high speed. [7] [10] It may appear in full color or as a simple outline. [12]