Pedestrian Wind Comfort Explained

What is Pedestrian Wind Comfort?

Put simply, pedestrian wind comfort is a measure of how local wind patterns impact the pedestrian experience. The speed, direction, and gustiness of winds can all affect how comfortable pedestrians will feel in a certain space.

As a general rule of thumb, higher wind speeds and – in particular – strong wind gusts – result in decreased pedestrian comfort. Very strong winds can affect pedestrians’ balance and stir up debris, posing a considerable safety risk.

When pedestrian-oriented locations (such as plazas and street fronts) experience uncomfortable and dangerous wind conditions it can hinder the profitability of nearby commercial activity by discouraging their use, typically requiring mitigation features to offset these negative impacts. 

How is Pedestrian Wind Comfort Measured?

In order to objectively predict pedestrians’ level of wind comfort, a set of Comfort Criteria is necessary. Aside from personal preference and individual needs, pedestrians’ tolerance for wind impacts is primarily dependent on factors such as the activities they are engaged in. For instance, someone who is walking may tolerate – or even appreciate – a light breeze, while a sitting person reading a paper may find such a breeze a nuisance. If winds in the area are too disruptive, mitigation features such as trees, landscaping and/or barriers may be recommended or even required. 

Wind Comfort Criteria approximate this effect by identifying maximum tolerable windspeed thresholds for various pedestrian activities. Furthermore, they will specify an “allowed exceedance” value, usually expressed as a percentage; this allowance specifies how often winds can exceed the threshold windspeed to remain in the ‘comfortable’ range.

In general, wind speeds for a given location are determined by aggregating hour-by-hour wind data with the local flow patterns established by the simulation or wind tunnel measurements. At baseline, wind conditions can be characterized by the steady-state wind speed (average intensity without gusts). Some criteria, such as RWDI’s Wind Criteria, combine the effects of that steady state wind speed with a characterization of the wind gusts to generate a more comprehensive measurement of the “perceived wind intensity”. 

Seasonal Analysis

An important fact to consider is that winds behave differently season-to-season. As a result, most Pedestrian Wind Comfort criteria base their threshold wind speeds on weather data from at least two seasons (generally Summer and Winter); and some criteria factor in data from all four seasons. 

Given these seasonal differences in wind characteristics, Orbital Stack’s CFD Engine enables you to choose up to four seasons to inform the pedestrian wind analysis (at least two are required for valid results).

Time of Day Filtering and Selection

Winds also behave differently throughout the day, where intensity is usually higher during the day. Furthermore, most pedestrian activity in outdoor spaces typically happens during the daytime. As a result, some Pedestrian Wind Comfort criteria exclude nighttime hours from their analysis. Some, however, use all 24 hours to inform their criteria. This is especially relevant for nightlife-oriented districts, where heavy pedestrian activity can be expected during nighttime hours.