Module 8 : Specialized Traffic Studies

Lecture 47 : Pedestrian Studies

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	Pedestrian Flow characteristic In many ways pedestrian flow are similar to those used for vehicular flow because it can be described in terms of familiar variables such as speed, volume, rate of flow and density. Other measures related specifically to pedestrian flow include the ability to cross a pedestrian traffic stream, to walk in the reverse direction of a major pedestrian flow, to manoeuvre generally without conflicts and changes in walking speed, and the delay experienced by pedestrians at signalized and unsignalized intersections. It is dissimilar to the vehicular flow in that pedestrian flow may be unidirectional, bidirectional, or multi-directional. Pedestrian do not always travel in clear "lanes" although they may do sometimes under heavy flow. Pedestrian Speed-Density Relationships The fundamental relationship between speed, density, and volume for pedestrian flow is analogous to vehicular flow. As volume and density increase, pedestrian speed declines. As density increases and pedestrian space decreases, the degree of mobility afforded to the individual pedestrian declines, as does the average speed of the pedestrian stream, it is shown in Fig. 1. Figure 1: Relationship between pedestrian speed and density Flow-Density Relationships The relationship among density, speed, and flow for pedestrians is similar to that for vehicular traffic streams, and is expressed in equation. $$Q_{ped}= S_{ped}* D_{ped}$$ (1) where, $Q_{ped}$= unit flow rate (p/min/m), $S_{ped}$= pedestrian speed (m/min), and $D_{ped}$= pedestrian density (p/$m^2$). Pedestrian density is an awkward variable in that it has fractional values in pedestrian per square meter. This relationship often expressed in terms of Space module(M) which is the inverse of pedestrian density. The inverse of density is more practical unit for analyzing pedestrian facilities ,so expression becomes $$Q_{ed} = \frac{S_{ped}}{M}$$ (2) where M in($m^2/ped$). The basic relationship between flow and space, recorded by several researchers, is illustrated in the Fig. 2. Figure 2: Relationship between pedestrian space & flow The conditions at maximum flow represent the capacity of the walkway facility. From Fig. 2, it is apparent that all observations of maximum unit flow fall within a narrow range of density, with the average space per pedestrian varying between 0.4 and 0.9 $m^2$/p. Even the outer range of these observations indicates that maximum flow occurs at this density, although the actual flow in this study is considerably higher than in the others. As space is reduced to less than 0.4 $m^2$/p, the flow rate declines precipitously. All movement effectively stops at the minimum space allocation of 0.2 to 0.3 $m^2$/p.