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Two Lane Highways

Posted by aditya | 8:39 PM | | 1 comments »

The bulk of our highway system is composed of two lane highways, and over 90 percent of the rural roads in United States are of this type. These two lane roads vary from low type roads, which follow the natural ground surface, to high speed primary highways with paved surfaces and stabilized shoulders. As traffic density, vehicle speeds, and truck widths from 4.8 m (16 ft) to the current recommended value of 7.2 m (24 ft) with 3 m (10 ft) stabilized or paved shoulders on either side along primary routes. Where lighter traffic volumes are expected, the American Association of State Highway and Transportation Officials recommends a range of minimum surface width, based on a combination of the design speed and traffic volume magnitude.

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The surrounding terrain and ability to pass or overtake a slower traveling vehicle play a large role in the operational adequacy of this type of roadway facility. Consider a two lane highway in a rural portion of Florida with long straight sections and no significant uphill grades and carrying a two way volume of approximately 500 vehicles per hour. Now consider a similar two lane highway in the mountain of Colorado, where passing is restricted and truck speeds are adversely affected by steep grades. The same type of highway in Florida will provide a better level of service, given an equivalent amount of traffic volume, primarily due to the surrounding conditions.


Highway and Transport Engineering
and this section is about Two Lane Highways
(refference : Wright, P.H, with contributions by James S. Lai, Peter S.Parsonson, Michael Meyer., Highway Engineering, 6th edition ,John Wiley & Sons, Inc.New York, 1996.)

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