# Decision Sight Distance

Written by Jerry Ratzlaff on . Posted in Civil Engineering

Decision sight distance, abbreviated as DSD, is the distance required for a driver to detect an unexpected obstacle or problem and react approperately.

## Decision Sight Distance formula

 $$\large{ DSD = 1.47 \; V \; t }$$

### Where:

 Units English Metric $$\large{ DSD }$$ = decision sight distance $$\large{ft}$$ $$\large{m}$$ $$\large{ V }$$ = design speed $$\large{\frac{ft}{sec}}$$ $$\large{\frac{m}{sec}}$$ $$\large{ t }$$ = total time for the maneuver (reaction time + maneuver time) $$\large{sec}$$ $$\large{s}$$