Evaluating Weaving Section Designs Using INTEGRATION

The current design procedure shown in Calculation 6 of the Highway Capacity Manual (HCM) requires an exhaustive analysis of a family of possible solutions. The design is selected on the basis of minimum speeds of weaving and nonweaving vehicles for different levels of service. In this paper the use of the INTEGRATION modeling tool to evaluate the same family of possible solutions is examined. Because INTEGRATION has the ability to determine volumes in addition to speeds, it was used to select the design solution based on the ratio of demand volume to capacity. Both procedures determined that five-lane Type B weaving sections greater than 610 m (2,000 ft) in length would provide level-of-service C for the origin-destination demand pattern found in Example Calculation 6 in Chapter 4 of the HCM. Analysis of the design results also showed that the number of lanes in the core area was the most critical factor in determining weaving section capacity. The length of the core area was also found to have an impact but was less important as core length increased. Finally, the type of weaving section was found to have the least impact on capacity, especially at core areas longer than 305 m (1,000 ft).