Improved freeway analysis techniques: flow fundamentals for freeway lane model

Currently the Institute of Transportation Studies (ITS) at the University of California is in the process of developing a freeway lane model which will predict flows by lane, and lane changes between lanes in the vicinity of ramp junctions and major weaves. To provide information for this model, ITS has studied certain characteristics of straight pipe sections of freeway (sections of freeway away from the influence of ramps) for three and four lane sites as described in this paper. These characteristics include lane distribution vs. flow, lane changing vs. flow, and speed vs. flow relationships for the two different sites. Additionally, this research further demonstrates the difference between the estimated value of capacity of a freeway lane cited in the Highway Capacity Manual (HCM) and the approximate capacity measured at the two sites, and compares the speed-flow curves developed at these sites to the 1985 HCM curve and the JHK curve.