13.5.2 Case B-Intersections with stop control on the minor road

Intersections with stop control on minor roads should consider three cases:
  • Left turns from minor road;
  • Right turns from minor road; and
  • Crossing a major road from a minor-road approach.
Intersection sight distance criteria for stop-controlled intersections are longer than stopping sight distance to allow the intersection to operate smoothly. Minor-road vehicle operators can wait until they can proceed safely without forcing a major-road vehicle to stop.
Multiple design vehicles and intersection layout, such as median width, should be considered when determining sight distance. If the design vehicle used for intersection sight distance is larger than a passenger car, then sight distance checks, for both larger vehicle and passenger vehicle, should be calculated.
Left turns from minor roads should use a time gap (
t
g
)(s) shown in
Table 13-2
. Right turns from a minor road should use a time gap (
t
g
)(s) shown in
Table 13-3
. Crossing the major road from a minor road approach should use a time gap (
t
g
)(s) shown in
Table 13-4
.
Table 13-2: Time-Gap for Left Turn from Stop
Design Vehicle
Time Gap (t
g
)(s) at Design Speed of Major Road
Passenger car
7.5
Single-unit truck
9.5
Combination truck
11.5
Notes:
Time gaps are for a stopped vehicle to turn left onto a two-lane highway with no median and with minor road approach grades of 3 percent or less. The time gaps are applicable to determining sight distance to the right in left-turn maneuvers. The table values should be adjusted as follows:
For multilane roadways or medians – For left turns onto two-way roadways with more than two lanes, including turn lanes, add 0.5 s for passenger cars or 0.7 s for trucks for each additional lane, from the left, in excess of one, to be crossed by the turning vehicle. Median widths should be converted to an equivalent number of lanes in applying the 0.5 and 0.7 s criteria presented above.
For minor-road approach grades – If the approach grade is an upgrade that exceeds 3 percent, add 0.2 s for each percent grade by which the approach grade exceeds zero percent.
Table 13-3: Time Gap for Right Turn from Stop
Design Vehicle
Time Gap (t
g
)(s) at Design Speed of Major Road
Passenger car
6.5
Single-unit truck
8.5
Combination truck
10.5
Notes:
Time gaps are for a stopped vehicle to turn right onto or to cross a two-lane roadway with no median and with minor-road approach grades of 3 percent or less. The table values should be adjusted as follows:
For minor-road approach grades – If the approach grade is an upgrade that exceeds 3 percent, add 0.1 s for each percent grade by which the approach grade exceeds zero percent.
Table 13-4: Time Gap for Crossing Maneuver from the Minor Road
Design Vehicle
Time Gap (t
g
)(s) at Design Speed of Major Road
Passenger car
6.5
Single-unit truck
8.5
Combination truck
10.5
Notes:
Time gaps are for a stopped vehicle to cross a two-lane highway with no median and with minor-road approach grades of 3 percent or less. The table values should be adjusted as follows:
For multilane roadways or medians—For crossing maneuvers that cross roadways with more than two lanes, including turn lanes, add 0.5 s for passenger cars or 0.7 s for trucks for each additional lane, from the left, in excess of two, to be crossed by the turning vehicle. Median widths should be converted to equivalent lanes.
For minor-road approach grades—If the approach grade is an upgrade that exceeds 3 percent, add 0.2 s for each percent grade by which the approach grade exceeds zero percent.