Spatio-temporal Difference Analysis on Environmental Parameters inside an Urban Road Tunnel during the Evening Rush Hour

The appearance of the evening peak in the tunnel leads to great changes in the spatio-temporal distribution of traffic flow. The environmental parameters and CO concentration in the tunnel are also further affected. In order to improve the environmental quality of the tunnel, the researchers conduct detailed field measurements of the air temperature, air velocity, CO concentration, CO₂ concentration, and particulate matter concentration in Yuhan Road tunnel during the evening rush hour. According to the test results, holidays have less traffic during peak hours and shorter evening rush hours than weekdays. As a result, the air velocity, temperature rise, and CO₂ increment on holidays are more stable and superior to those on workdays. During working days, the air velocity in the tunnel is reduced by 1.7~3.2 m/s, and the longitudinal temperature is increased by 6.1~7.7 ℃. As the delay time of vehicle speed increases, the delay time of air velocity, temperature rise, and CO₂ increment shows an increasing trend, and the maximum delay time can reach 70 min. The delay time from 20 min after the beginning of the traffic peak to 70min after the end of the traffic peak should be considered for tunnel ventilation on weekdays.