A CAPACITY ESTIMATION METHOD FOR TWO-LANE, TWO-WAY HIGHWAYS USING SIMULATION MODELING

Open Access
Author:
Kim, Joonhyo
Graduate Program:
Civil Engineering
Degree:
Doctor of Philosophy
Document Type:
Dissertation
Date of Defense:
January 30, 2006
Committee Members:
  • Eric Todd Donnell, Committee Member
  • Kevin M Mahoney, Committee Member
  • Ageliki Elefteriadou, Committee Chair
  • Martin T Pietrucha, Committee Chair
  • Deborah Jean Medeiros, Committee Member
Keywords:
  • highway
  • two-way
  • two-lane
  • estimation
  • capacity
  • simulation
Abstract:
The 2000 HCM (Highway Capacity Manual) suggests the capacity of two-lane, two-way highways to be 3,400 pcph for both directions and 1,700 pcph for one direction. In fact, higher traffic volumes have been observed in previous studies. Also, a single capacity value cannot reflect the variety of traffic, geometric, and driver conditions that may exist on two-lane, two-way highways. In addition, observation of capacity is difficult, so a new simulation model is developed in this study. Capacity of two-lane, two-way highways is estimated using a microscopic simulation model, which is developed with MATLAB 6.5. Due to the absence of capacity data, the newly developed simulator, TWOSIM (Two-lane, two-way highway SIMulator) is compared to existing analytical tools such as TWOPAS and 2000 HCM method for verification of its performance. Using TWOSIM, the capacity (i.e., 100 percent no-passing zone, all passenger cars and commuters, level tangent section, 12’ lane width, 6’ shoulder width) for one direction is estimated to be 2,100 pcph at 60 and 70 mph average free flow speeds, 2,000 pcph at 50 mph average free flow speed, and 1,850 pcph at 40 mph average free flow speed. These estimated capacities are higher than the 2000 HCM’s estimated capacity for one direction. The presence of passing zones was not found to increase capacity. Additional capacity values are estimated to account for the presence of a driveway, a horizontal curve, a grade, and various percentages of trucks in the traffic stream. These treatments were found to reduce capacity (5~38 percent reduction in capacity). Based on the results, recommendations are provided regarding changes in the 2000 HCM, as well as in the model calibration and algorithm improvement of TWOSIM.