Table 1: Traffic Flow Along Coordinated Arterials
Synchro already models coordinated signals and therefore does not require additional data to calculate the Platoon Ratio. The user should, however, be sure to code the following settings located in the Synchro Timing Settings window:
- Reference Phase: Select the phase(s) from which offsets should be calculated. Many controllers refer to this as the coordinated phase(s). This is usually the phase for the main street. Phases 2 and 6 are commonly assigned to the main street and used as the coordinated phases.
- Offset: The current offset for the intersection is the amount of time in seconds that the reference phase begins (or ends) after the nearby adjacent intersections.
- Reference to: Select the point from which offsets should be referenced. Two of the most common are the Beginning of Green and Beginning of Yellow.
- Upstream signalized coordinated intersection within 0.60 mile
- Upstream intersection and study intersection must have equal, double, or half Cycle Lengths
- Reference phase of upstream intersection points towards study intersection
Rp = P/(g/C)
Rp = platoon ratio
P = proportion of vehicles arriving during the green indication (decimal)
g = effective green time (s)
C = cycle length
In many cases, the platoon ratio will have a significant impact on the resulting delay and queue length. Users are encouraged to review this value carefully.
To demonstrate the relationship between vehicles arriving on green and the platoon ratio, let’s consider vehicles traveling along Main Street (see image below) and observe the flow patterns shown on the time-space diagram. The calculated values for the eastbound (EB) and westbound (WB) platoon ratios at 2nd, 3rd, and 4th Street have also been included. This allows one to visualize the relationship between arrival on green and the platoon ratio.