Sight Distance

Sight Distance

• SSD : is the sum of two distances: perception reaction time, and the vehicle stopping distance.
• The curve length should provide enough SSD at design speed, and minimize cut and fill if possible.
• AASHTO design standards (1984): H1= 3.5, drivers eye height, and obstruction height H2 = 0.5 ft., SSD given in tables.

fig 3.5 , 3-6 mannering

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