# Intersection Sight Distance

Written by Jerry Ratzlaff on . Posted in Civil Engineering

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 $$\large{sec}$$ $$\large{s}$$