Module 4 : Macroscopic And Mesoscopic Traffic Flow Modeling

Lecture 19 : Traffic Progression Models

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Platoon Ratio

The platoon ratio denoted as Rp, is a numerical value used to quantify the quality of progression on an approach. The platoon ratio represents the ratio of the number of vehicles arriving during the green phase to the proportion of the green interval of the total cycle. This is given by

$$R_p=P\frac{C}{g}$$ (1)

where, P = Proportion of all vehicles during green time, C = Cycle length, g = Effective green time. Its value ranges from 0.5 to 2.0. It is used in the calculation of delays, capacity of an approach. The arrival types range from 1 (worst platoon condition) to 6 (the best platoon condition). The platoon ratio approximates the arrival type and the progression quality. For example HCM (2000) has suggested the following relationship between platoon ratio and arrival which is as shown in Table 1.

Table 1: Relationship between Arrival Type and Platoon Ratio

Arrival	Range of platoon	Default value$(R_p)$	Progression quality
type	ratio$(R_p)$
1	$\leq 0.50$	0.333	Very poor
2	$> 0.50-0.85$	0.667	Unfavorable
3	$> 0.85-1.15$	1.000	Random arrivals
4	$> 1.15-1.50$	1.333	Favorable
5	$> 1.5-2.00$	1.667	Highly favorable
6	$> 2$	2.000	Exceptional