Parameters Influencing Lane Flow Distribution on Multilane Freeways in PTV Vissim

In a parameter study, we systematically varied parameter values, and quantified the resulting traffic flow in each individual lane. We modeled two-, three-, and four-lane freeway sections with the microscopic traffic flow simulation tool PTV Vissim. We compared the results with findings from literature. Simulations using car following model Wiedemann 99 fit better to empirical studies than those using Wiedemann 74. Empirically determinable parameters, that have a relevant influence on lane flow distribution are desired speed distributions (mean for heavy-duty vehicles and standard deviation for cars), heavy-duty vehicle share, and the gradient of the section. Additionally, the driving behavior parameters CC1 (headway time), CC3 (threshold for entering following), and safety distance reduction factor have an influence. As CC1 is one of the most relevant parameters for calibrating capacity, CC3 and the safety distance reduction factor remain for lane flow adjustment

Design Hourly Volume Estimation at Freeway Nodes from Short-Term Traffic Counts

This paper extends the concept of a design hourly volume (DHV) which is derived from the ‘nth hour’ to a concept based on the nth highest saturated hour. To calculate this nth highest saturated hour at each ramp junction of a node, permanent traffic counts (PTC) are necessary on all ramps and the main lanes. In practice, such counts are often not available. For such cases, the German HCM proposes a method that enables the estimation of the design hourly volume through short-term traffic counts (STC) and the extrapolation of the results using available PTC in the vicinity. Within the scope of this study, it is examined how accurate the required nth highest saturated hour can be estimated with this method and similar concepts. Furthermore, it is investigated to what extent the number and the location of the available PTC affect the accuracy of the estimation. Scenarios without PTC are also considered. The evaluation is based on a database with a total of 72 freeway nodes for which PTC data from three years (2017-2019) are processed. The results show that the estimation of the nth highest saturated hour with the method of the German HCM works accurately, even if only one PTC is available on each inflowing approach. The results further indicate that STC are crucial to achieve accurate results when only few PTC are available. Acceptable results are also obtained by STC of one week, even without a projection at a PTC