13.5.6 Case F-Left turns from the major road
A left turn from the major road across opposing traffic when permitted, including intersections and driveways, should have sufficient sight distance to accommodate the maneuver. Sight distance design should be based on a left turn by a stopped vehicle since a vehicle that turns left without stopping would need less sight distance.
Left turns from the major road should use a time gap (
t
)(s) shown in
.g
If stopping sight distance has been provided continuously along the major road and if sight distance for Case B (Stop control) or Case C (Yield control) has been provided for each minor-road approach, sight distance will generally be adequate for left turns from the major road. On three-leg intersections or driveways located near a horizontal curve, it is recommended to check the left turn sight distance for possibility of obstructions in the median.
Design Vehicle | Time Gap (t g )(s) at Design Speed of Major Road |
Passenger car | 5.5 |
Single-unit truck | 6.5 |
Combination truck | 7.5 |
Notes: | |
Time gaps are for a stopped vehicle turning left from a two-lane highway with no median For multilane and/or divided roadways—For left turns on two-way roadways across more than one opposing lane, including turn lanes, add 0.5 s for passenger cars or 0.7 s for trucks for each additional lane to be crossed in the left-turn maneuver in excess of one lane. Where the left-turning vehicle must pass through a median, the median width should be converted to an equivalent number of lanes. | |