People in urban areas frequently use parks for recreation and outdoor activities. Owing to the complexity of the outdoor environment, there have only been a few attempts to understand the effect of the thermal environment on people's use of outdoor spaces. This paper therefore seeks to determine the relationship between the thermal environment, park use and behavioural patterns in an urban area of Sweden. The methods used include structured interviews, unobtrusive observations of the naturally occurring behaviour and simultaneous measurements of thermal comfort variables, i.e., air temperature, air humidity, wind speed and global radiation. The thermal environment is investigated through the mean radiant temperature (Tmrt) and the predicted mean vote (PMV) index. The outcome is compared to the subjective behaviour and thermal sensation of the interviewees. It is found that the thermal environment, access and design are important factors in the use of the park. In order to continue to use the park when the thermal conditions become too cold or too hot for comfort, people improve their comfort conditions by modifying their clothing and by choosing the most supportive thermal opportunities available within the place. The study also shows that psychological aspects such as time of exposure, expectations, experience and perceived control may influence the subjective assessment. Comparison between the thermal sensation of the interviewees and the thermal sensation assessed by the PMV index indicates that steady-state models such as the PMV index may not be appropriate for the assessment of short-term outdoor thermal comfort, mainly because they are unable to analyse transient exposure.

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The paper demonstrates the relevance of sky view factor analysis in urban canyons to thermal features of the surface and air in the urban canopy layer at night. The result of the study, made in the city of Malmo (population about 230,000) in southern Sweden, indicates, among other things, that the street geometry and its regional distribution within the city area plays a fundamental role in generating the street surface temperature pattern of the city, its 'surface heat island'. The paper also demonstrates a digital image processing technique of determining the sky view factor from fish-eye lens photographs.KEY WORDS Urban heat island Street canyon geometry Street temperature Sky view factor Fish-eye lens photographs

A method for deriving quantitative relationships between road slipperiness, traffic accident risk and winter road maintenance (WRM) activity is described. The method is also applied to data from an area in southern Sweden. If a specific type of road slipperiness represents a large accident risk despite high WRM activity it is important to increase public awareness during such periods. If the type of slipperiness represents a large accident risk but is accompanied by low WRM activity, it is also important to increase the WRM to reduce the accident risk. In the method, a road slipperiness classification, based on atmospheric processes, is used to classify the road conditions at the time an accident occurred. The road condition is classified either as non-slippery or as one out of 10 types of slipperiness. Data for the slipperiness classification are taken from the Swedish Road Weather Information System (RWIS). Results from this study show that the traffic accident risk was different for different types of road slipperiness. Highest accident risk was associated with road slipperiness due to rain or sleet on a frozen road surface. When accidents occurred in these situations, there was always high WRM activity. This indicates that, in order to reduce the accident rate during these situations, public awareness must be increased by providing information to drivers. The study also demonstrates the benefits of applying a standardized road slipperiness classification to all kinds of sources of road safety information, such as a RWIS, traffic accident reports and WRM reports. With a standardized and objective classification of the road conditions and digitally stored data, all evaluations are easily conducted. KEY WORDS: Road slipperiness · Traffic accidents · Winter road maintenanceResale or republication not permitted without written consent of the publisher CLIMATE RESEARCH