Decision Sight Distance

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)	\(\large{sec}\)	\(\large{s}\)