Geometric Approach to Modeling Vehicular Speeds through Simple Freeway Weaving Sections

1 a typical simple one-side weaving section, as shown in Figure 1, the geometric variables of the weaving section are the length of the weaving section, L, and the number of lanes within the weaving section, N. Length of the weaving section is measured from a point where the entrance gore is 2 feet wide to a point where the exit gore is 12 feet wide. Vehicular flow is categorized into four general movements in the userbased approach prevalent among current weaving operational analysis and design procedures, such as the 1985 Highway Capacity Manual (HCM) weaving procedure’ and the JHK & Associates weaving procedurez~. One movement involves vehicles originating from the freeway approach to the weaving section and exiting at the freeway egress. The volume of traffic performing this movement is labeled V,. The second movement originates from the freeway approach and ends at the exit ramp; its volume is labeled V.. The third movement begins at the entrance ramp and terminates at the freeway egress; this volume is labeled V,. The entrance ramp to exit ramp movement is the fourth movement; it involves volume V~. In a simple onesided weaving section, the sum of the V, and V~ movement volumes is the total weaving volume (VW).The sum of the V, and V. volumes is equal to the total nonweaving volume (V~W). Current userbased weaving procedures, however, do not predict average running nonweaving speeds well. In a recent evaluation of the procedures, a poor to moderate correlation existed between the speeds derived from the nonweaving speed models and the average running nonweaving speeds observed in the field.’ In Figure 1, the lanes entering the weaving section are denoted by a letter. The entrance ramp lane is labeled A; the freeway lane closest to the entrance ramp lane is labeled B; and the remaining freeway lanes are labeled in descending order. If the entrance ramp has more than one lane, the next lane beside lane A is labeled B’ and any other lanes are subsequently labeled with the prime mark in descending order. The volume entering the weaving section via lane A is designated VA; lane 1?, V., and so on. Model Development