Boston (BPDA) Pedestrian Wind Criteria

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The Boston Planning and Development Agency (BPDA) has adopted two standards for assessing the relative wind comfort of pedestrians. First, the BPDA wind design guidance criterion states that an effective gust velocity (hourly mean wind speed +1.5 times the root‑mean‑square wind speed) of 31 mph should not be exceeded more than 1% of the time.

The second set of criteria used by the BPDA to determine the acceptability of specific locations is based on the work of Melbourne. This set of criteria is used to determine the relative level of pedestrian wind comfort for activities such as sitting, standing, or walking.  The criteria are expressed in terms of benchmarks for the 1-hour mean wind speed exceeded 1% of the time.

The consideration of wind in planning outdoor activity areas is important since high winds in an area tend to deter pedestrian use.  For example, winds should be light or relatively light in areas where people would be sitting, such as outdoor cafes or playgrounds.  For bus stops and other locations where people would be standing, somewhat higher winds can be tolerated.  For frequently used sidewalks, where people are primarily walking, stronger winds are acceptable.  For infrequently used areas, the wind comfort criteria can be relaxed even further.  The actual effects of wind can range from pedestrian inconvenience, due to the blowing of dust and other loose material in a moderate breeze, to severe difficulty with walking due to the wind forces on the pedestrian.

The wind climate found in a typical downtown location in Boston is generally comfortable for the pedestrian use of sidewalks and thoroughfares and meets the BPDA effective gust velocity criterion of 31 mph.  However, without any mitigation measures, this wind climate is likely to be frequently uncomfortable for more passive activities such as sitting.

This study involved state‑of‑the‑art measurement and analysis techniques to predict wind conditions.  Nevertheless, some uncertainty remains in predicting wind comfort, and this must be kept in mind. For example, the sensation of comfort among individuals can be quite variable.  Variations in age, individual health, clothing, and other human factors can change a particular response of an individual.  The comfort limits used in this report represent an average for the total population.  Also, unforeseen changes in the project area, such as the construction or removal of buildings, can affect the conditions experienced at the site.  Finally, the prediction of wind speeds is necessarily a statistical procedure.  The wind speeds reported are for the frequency of occurrence stated (1% of the time).  Higher wind speeds will occur but on a less frequent basis.