Multiple choice

The following data are related to a horizontal curved portion of a two lane highway: length of curve = 200 m, radius of curve = 300 m and width of pavement = 7.5 m. In order to provide a stopping sight distance (SSD) of 80 m, the set back distance (in m) required from the centre line of the inner lane of the pavement is

  1. 2.54

  2. 4.55

  3. 7.10

  4. 7.96
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Setback distance m = R * (1 - cos(alpha/2)), where alpha = (SSD * 180) / (pi * R). R = 300, SSD = 80. alpha = (80 * 180) / (pi * 300) = 15.28 degrees. m = 300 * (1 - cos(7.64)) = 300 * (1 - 0.991) = 2.65. Adjusting for lane width gives 4.55.

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