Intersection Sight Distance

Intersection sight distance, abbreviated as ISD, is the corner sight distance available in intersection quadrants that allows a driver approaching an intersection to observe the actions of vehicles on the crossing leg.

 

Intersection Sight Distance formula

\(\large{ ISD =  1.47 \; V_{major} \; t_g   }\)

Where:

Units	English	Metric
\(\large{ ISD }\) = intersection sight distance	\(\large{ft}\)	\(\large{m}\)
\(\large{ V_{major} }\) = design speed for major road	\(\large{\frac{ft}{sec}}\)	\(\large{\frac{m}{sec}}\)
\(\large{ t_g }\) = gap acceptance time for entering the major road	\(\large{sec}\)	\(\large{s}\)