Impact of Rainfall on Urban Traffic Flow based on Probe Vehicle Data in Bangkok

Adverse weather frequently affects the capacities and travel speeds on roadways, which result in worsened traffic congestion and incurred productivity loss. Further, with climate change predicted to increase rainfall in various cities in Southeast Asia, the risk of flood damage in this region is not only anticipated to increase and affect urban function but may also significantly aggravate daily traffic flow. This study highlighted an analysis of the effect of rainfall on urban traffic flow through the use of probe vehicle data and rainfall data in the center of Bangkok, which is known in Southeast Asia for problems with respect to maintenance of pumps and drainage channels and for many flooded roads after heavy rainfalls. The experimental results demonstrated that the average travel speed decreased by 0.02 km/hour per 1 mm of daily rainfall. In particular, at the time of peak traffic demand, the travel speed was notably reduced when passengers preferred automobile traffic. In 2018, the economic loss estimate in central Bangkok due to annual rainfall was approximately 0.01% of the city’s GDP. Future rainfall forecast data makes it possible to assess the risk of climate change on urban traffic flow.