| Title | Development of Improved Methods for Capacity Analysis of Signalized Urban Intersections (1/2) |
| Dept | Transportation Planning and Land Transport Division |
| Year | 2006 |
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| Summary | A two-year research project was initiated in January 2005 by the Institute of Transportation to revise Chapter 13 of the 2001 Taiwan Area Highway Capacity Manual (HCM). The following tasks were conducted in the first year: (1) review of literature concerning the methodologies for capacity and level-of-service analysis of signalized intersections (2) collect and synthesize field data to identify the traffic characteristics at signalized urban intersections (3) develop analytical models for estimating the capacities of straight-through lanes, unopposed left-turn lanes, shared left-turn and straight-through lanes and shared right-turn and straight-through lanes (4) collect field samples of queue length and traffic delays under varying conditions to test the Highway Traffic Systems Simulation Model (HTSS) and (5) use observed queue discharge behavior to calibrate the HTSS model. The field data show that the peak hour factor at an urban intersection tends to increase with flow rate, but essentially, it falls in the range of 0.8 to 0.95 once the flow rate exceeds 800 vphpl. The field data also show that the traditional concept of saturation flow is not appropriate for modeling the capacity of the traffic lanes at a signalized intersection. A new approach to modeling lane capacity will be incorporated into revised Chapter 13 of the HCM. Several models have already been developed for estimating the capacities of certain types of traffic lanes. And the HTSS model is being calibrated based on the most current field data. The effort of developing analytical models for capacity estimation and calibrating the HTSS model for analyzing the operations of signalized intersections will continue in the second year of this project. This report documents the tasks and the findings of the first-year research effort. |
| Post date | 2006/10/17 |
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