Jose M Ulerio

Capacity of Freeway Weaving Segments

The analysis methodology for freeway weaving segments specified in the current Highway Capacity Manual (HCM 2000) provides a cumbersome set of multipage tables for the determination of weaving segment capacity. As part of NCHRP Project 3-75, Analysis of Freeway Weaving Sections, a more straightforward approach to estimating weaving segment capacity has been developed. This paper presents the methodology and discusses its background and development. The methodology continues to define capacity as in the HCM 2000: capacity occurs primarily when a density of 43 passenger cars per mile per lane is reached. Various other controls in HCM 2000 are replaced with revised limits on the number of weaving vehicles that can be accommodated in a weaving segment. The methodology substitutes a regression-based equation for the cumbersome tables of the HCM 2000.

Level of Service Analysis of Freeway Weaving Segments

This paper reports on the product of NCHRP Project 3-75, which resulted in the development and calibration of new models for freeway weaving segments, including a draft chapter for the forthcoming Highway Capacity Manual (HCM). The most critical element of the current procedures in the HCM 2000 is the prediction of the average speeds of weaving and nonweaving vehicles in the weaving segment. These speeds are converted to an overall density for the segment that determines the prevailing or expected level of service. The proposed method does away with the strict assignment of weaving geometries to one of three configuration categories and also the need to determine whether the operation of the weaving segment is constrained or unconstrained. That approach led to the need to calibrate 12 equations to predict speeds. In research, this greatly increased the size of the desirable database for calibration. The new approach relies on the prediction of lane-changing activity within the weaving segment to quantify the impact of configuration and type of operation on resulting speeds and densities.

Weaving Area Analysis in Year 2000 Highway Capacity Manual

The development of weaving area analysis procedures for the next edition of the Highway Capacity Manual, which is to be published in 2000, is described. Weaving has proved to be one of the most complex types of operation to analyze consistently. Although many studies and investigations have examined weaving areas, no single comprehensive research document exists that has resulted in an analysis procedure that has withstood the test of time and application, despite many attempts to do so. As the publication of the Highway Capacity Manual for the Year 2000 (HCM 2000) nears, weaving analysis procedures continue to be influenced by a variety of historic studies and documents and by several databases. None of these is statistically adequate given the number of variables involved. Thus, procedures continue to require the application of the professional judgment of the members of the Committee on Highway Capacity and Quality of Service of the Transportation Research Board. Documentation for the analyses and judgments that support the analysis procedure as it is recommended to appear in the HCM 2000 is given in this paper.

Comparative Analysis of FRESIM and 1994 Highway Capacity Manual Models for Ramp Junctions with an Independent Data Base

The results of a comparative analysis of the 1994 Highway Capacity Manual (94HCM) ramp junction models and the FRESIM simulator model with an independent data base are described. The analysis was done as part of NCHRP Project 3-37 (Phase II), whose objective was to identify and investigate common ranges of application, consistency of internal logic, consistency of results, and potential modification to both the 94HCM and the FRESIM models. The results indicate that FRESIM may be a reasonable tool for predicting operational parameters within the area of ramp junctions for isolated ramps, although they also indicate that FRESIM may not be sensitive enough to some geometric parameters to be used confidently in its current form.