Comparison of the bioclimatological Impact/stress in two different subway systems New York City (USA) and Dortmund (Germany)

Bioclimatological load due to stress arising from heat or coldness and sultriness has often been studied in urban climatology and interactions and influences on human beings are mostly known. On the contrary, there is relatively little information on such load caused by stress in underground public transportation. Every day many people spend their time inside such underground systems (stations, tunnels, entrances and exits) and trains. Thus, it is of particular importance to study and analyse the respective loads in underground systems as well.

A measurement program planned to study such influences and interactions was put up for the Subway of New York City in summer 1998, while a comparable program began in the underground public transportation system of Dortmund, Germany in winter 1999/2000.

At the beginning, the investigation aimed to determine the thermal load inside subway stations and to quantify temperature differences between the different levels of more complex stations, the air outside the subway system, and inside the trains, respectively. Measurements were made in summer and winter; in addition to air temperature, the infrared radiation temperature of ground surfaces, ceilings, and walls were recorded; furthermore, relative humidity was determined.

Results clearly show that passengers are exposed to high temperature stresses and often have to bear extreme short-term fluctuations of air temperature of orders of 10 to 20 K as well; especially the latter have a very high load potential to passengers. Entering or leaving the stations as well as getting off the trains has to be seen as being very critical situations in this context as the biggest temperature differences could be observed in these areas. Additionally, long periods where passengers stay inside the stations while waiting for their trains can increase thermal load. This is due to the fact that station walls are an important source for heat (they show radiation temperatures of more than 50°C) in addition to the air temperatures which are usually greater than 30°C.