Left turn traffic affects the control delay and the chosen number of phases. Permitted and protected
left turn traffic are usually decided as a function in left turn traffic volume and traffic volume of the opposite
direction. This research studies the effect of two variables on the relation between left turn traffic and the
control delay. These variables are the average lane volume and the percentage of difference in traffic volume
between opposite directions. More than 160 model runs are done on Synchro software to record the
relationships between these three variables. Three sets of curves are extracted from this analysis. The first set
explains the effect of the value of the average lane volume on the relationship between control delay and the
left turn traffic. This set is repeated for different values of difference between opposite traffic volume. The
second set of curves explains the effect of the percentage of difference between opposite direction on the
relationship between the control delay and the left turn traffic. This set is repeated for different values of traffic
volume. The third set of curves summaries all variables that affect the relationship between left turn traffic and
the control delay. The research concluded that the value of average lane traffic volume affects the relationship
between the control delay and the percentage of left turn traffic. The same conclusion is acquired for the effect
of percentage of difference between opposite traffic volume on the relationship between the control delay and
the percentage of left turn. The research introduces guides for protecting and permitting left turn traffic.