Abstract
In Taiwan, the depressed urban streets were usually sited on intersections in urban area to bypass facilities and avoid the traffic congestion. The traffic flows of depressed urban streets were treated as the un-interrupted flows in the Chapter 10 "Depressed Urban Streets" of 2011 Taiwan Highway Capacity Manual (2011 HCM). But, the signals were usually settled in the depressed urban street upstream and downstream, and the traffic operation was affected by the signal control obviously. The analysis procedure in 2011 HCM was not realistic and practical. In order to explore the characteristics of the depressed urban streets and find the adjustment factor of slope for revising HCM, this study conducted the field data collection in 9 sites in Taipei metropolitan area. It was found that the queue discharge rates of the straight-through lanes of these streets were significantly lower than those of flat streets, and were affected by geometric design. And these findings could be useful for revising works.
