Module 8 : Specialized Traffic Studies
Lecture 47 : Pedestrian Studies
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Speed-Flow Relationships

The following Fig. 1 illustrates the relationship between pedestrian speed and flow. These curves, similar to vehicle flow curves, show that when there are few pedestrians on a walkway (i.e., low flow levels), there is space available to choose higher walking speeds. As flow increases, speeds decline because of closer interactions among pedestrians. When a critical level of crowding occurs, movement becomes more difficult, and both flow and speed decline.
Figure 1: Relationships between Pedestrian Speed and Flow
\begin{figure} \centerline{\epsfig{file=qfPedestrianSpeedFlow.eps,width=8 cm}} \end{figure}
The Fig. 2 confirms the relationships of walking speed and available space, and suggests some points of demarcation for developing LOS criteria. The outer range of observations indicates that at an average space of less than 1.5 $ m_2$/p, even the slowest pedestrians cannot achieve their desired walking speeds. Faster pedestrians, who walk at speeds of up to 1.8 m/s, are not able to achieve that speed unless average space is 4.0 $ m_2$/p or more.
Figure 2: Relationships between Pedestrian Speed and Space
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Pedestrian Space Requirements

Pedestrian facility designers use body depth and shoulder breadth for minimum space standards, at least implicitly. A simplified body ellipse of 0.50 m * 0.60 m, with total area of 0.30 $ m_2$ is used as the basic space for a single pedestrian, as shown in Fig. 3 this represents the practical minimum for standing pedestrians. In evaluating a pedestrian facility, an area of 0.75 $ m_2$ is used as the buffer zone for each pedestrian. A walking pedestrian requires a certain amount of forward space. This forward space is a critical dimension, since it determines the speed of the trip and the number of pedestrians that are able to pass a point in a given time period. The forward space in the Fig 4 is categorized into a pacing zone and a sensory zone.
Figure 3: Pedestrian body ellipse
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Figure 4: Pedestrian walking space requirement
\begin{figure} \centerline{\epsfig{file=qfPedWalkingSpace.eps,width=8 cm}} \end{figure}

Pedestrian Walking Speed

Pedestrian walking speed is highly dependent on the proportion of elderly pedestrians (65 years old or more) in the walking population. If 0 to 20 per cent of pedestrians are elderly, the average walking speed is 1.2 m/s on walkways. If elderly people constitute more than 20 per cent of the total pedestrians, the average walking speed decreases to 1.0 m/s. In addition, a walkway upgrade of 10 per cent or more reduces walking speed by 0.1 m/s. On sidewalks, the free-flow speed of pedestrians is approximately 1.5 m/s. There are several other conditions that could reduce average pedestrian speed, such as a high percentage of slow-walking children in the pedestrian flow.

Pedestrian Start-Up Time and Capacity

A pedestrian start-up time of 3 s is a reasonable midrange value for evaluating crosswalks at traffic signals. A capacity of 75p/min/m or 4,500p/h/m is a reasonable value for a pedestrian facility if local data are not available. At capacity, a walking speed of 0.8 m/s is considered a reasonable value.