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"The width of travel lanes is limited by the physical dimensions of automobiles and
trucks to a range between 2.7 and 3.6 m (9 and 12 ft)." Surrounding context and speed are factors determining the necessary minimum lane width.
The width of travel lanes is limited by the physical dimensions of automobiles and trucks to a range between 2.7 and 3.6 m (9 and 12 ft). Generally, as the design speed of a highway increases, so must the lane width to allow for the lateral movement of vehicles within the lane. However, constricted right-of-way and other design restrictions can have an impact on this decision. Chapter IV of the Green Book recognizes the need for flexibility in these cases:
"Although lane widths of 3.6 m are desirable on both rural and
urban facilities, there are circumstances that necessitate the use
of lanes less than 3.6 m wide. In urban areas where right-of-way
and existing development become stringent controls, the use of
3.3 m lanes is acceptable. Lanes 3.0 m wide are acceptable on
low-speed facilities. Lanes 2.7 m wide are appropriate on
low-volume roads in rural and residential areas."
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