Temporal and Spatial Analysis of Peak-concentration Times for NO and NO2 in Morning and Evening Events: A Case Study of Surabaya City.

The peak-concentration times of air qualityindicators, reflecting transportation activity, were investigated using multilevel model at five ambient-air-quality monitoring stations in Surabaya, Indonesia. It was conducted from 2001 to 2002. It aimed to obtain spatial and temporal factors that affect the peak-concentration time.The results obtainedare helpful for picturing traffic congestion in each zone using air-quality-monitoring data (i.e., NO concentrations). Spatially, it was found that congestion occurred later in the morning in suburban zones than in the three other zones (e.g., 55 and 14 min later than in the city center) and 16 and 57 min earlier in the evening in the suburban zones than in the city center, suggesting tendency of delayed departure and earlier return on the suburban. In terms of season, for instance, in the highway zone, the peak time in the morning was as much as 9 min earlier in the dry season than in the wet season, and the peak time in the evening was 17.5 min later in the dry season than in the wet season. This suggests that traffic congestion occurred over a longer period of the day during the dry season. Day-to-day variation did not significantly affect the peak times. However on Sunday, the peak times in morning and evening are lowest and highest for all zones. This might be due to family-related activities, such as leisure and recreational activities. The full model did not marksignificant improvement over the null model, meaning that more variables need to be incorporated to explain the variability of the peak time. [ABSTRACT FROM AUTHOR]

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