Analysis of the Weaknesses in the Present Freeway Capacity Models for Sweden

The aim of the work is to scrutinize the present Swedish capacity manual and new models from a project in the early 2000's. It only covers freeway facilities. By using new and extended empirical data the models that have to be improved can be further developed. The result shall be the freeway models in the new Swedish Capacity Manual. The manual for freeway facilities include a time-space model for bottleneck analysis of urban and rural freeways. The work has been based on the documentation for the present models. The models have also been compared to other international models to check the reasonableness. The project includes three parts, freeway mainline section, freeway weaving and freeway merging. The review of the models revealed several deficiencies. - The Swedish capacity model for main line section doesn't take into account the gradient, which is an important factor and is one of the most significant parameters according to German experiences. - Another large knowledge gap is the fact that the capacity model doesn't take into account lane width and distance to obstacle. - The model for weaving has one large weakness, it is based on empirical data where the on-ramp flow is almost equal with the off-ramp flow. The model has then been design with a total weaving flow, which means that the model is insensitive to flow cases where e. g. the on-ramp flow is much larger than the off-ramp flow. - The model for on-ramp merging does only take into account the on-ramp flow, other international models also have ramp length. The work with the new capacity models during 1998-2001 had a lack of empirical data, which gave the result that relation between different parameters where difficult to find. E. g. the weaving model has only 6 hours empirical data. The models should preferable add the following parameters: - Gradient for main line - Lane width - Distance to obstacle - Separate on-and off-ramp flow in the weaving model - On-ramp length With the data collection system
QC 20120405