Pedestrian Wind Comfort and Safety

Pedestrian Wind Comfort (PWC) and Pedestrian Wind Safety (PWS) are important aspects of urban planning and design, as they directly affect the livability and usability of outdoor spaces. High wind speeds can cause discomfort, reduce the attractiveness of public areas, and in extreme cases pose safety risks. In simple terms, wind comfort deals with everyday nuisance winds, while wind safety concerns rare but dangerous strong winds.

Assessing PWC and PWS involves combining regional wind climate data with detailed modeling of local wind flow around a site, then evaluating the results against established comfort criteria. In practice, the process includes:

1. Wind Simulations
   Multiple CFD simulations are carried out for different wind directions to model wind flow around buildings and open spaces. We use 8 wind directions for draft simulations and 16 wind directions for detailed simulations.

2. Regional Meteorological Wind Statistics
   A statistical wind rose, typically based on long-term weather station records, provides the frequency of wind directions and speeds for the site. This defines the incoming wind climate (e.g. how often strong winds occur from each direction). → In ArchiWind, the default option is to use ArchiWind’s own historical climate data (via open-meteo and MeteoBlue, depending on your subscription).
   Alternatively, you can provide a custom climate file (for example from a local weather measurement mast or other dataset), either as EPW file or IL GovMap CSV file.

3. Comfort and Safety Criteria Application
   A defined standard (e.g. Lawson 2001, NEN 8100, IS 5281) is applied, which assigns thresholds for acceptable wind speeds and exceedance frequencies depending on activity type or risk level.
   Finally, the modeled local wind speeds are statistically combined with the meteorological data to determine how often certain wind speed thresholds will be exceeded at pedestrian level.

   Example of a comfort criteria: Lawson LDDC

   Category	Wind Speed	Probability	Effect	Color
   A	≤ 2.5 m/s	> 95%	Frequent Sitting
   B	≤ 4 m/s	> 95%	Occasional Sitting
   C	≤ 6 m/s	> 95%	Standing
   D	≤ 8 m/s	> 95%	Walking
   E	> 8 m/s	> 5%	Uncomfortable (and/or Unsafe)

4. Classification and Mapping
   Each computational cell is assigned a comfort or safety class, and these are projected onto a map at pedestrian height (we use 2 m above the ground or building rooftops). The result is a color-coded map showing the distribution of wind comfort and safety across the study area.