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Splitting Motorways : A Capacity and Safety Evaluation of Lane Configuration Types in Motorway Splits
Boender, N. (2025) Splitting Motorways : A Capacity and Safety Evaluation of Lane Configuration Types in Motorway Splits.
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| Abstract: | The design of motorways is captured in guidelines, such as the ROA for the Netherlands. These provide, amongst others, information on standard designs of several motorway elements. One of these elements is a motorway split, a point on a motorway where the original road is split in two new roads (branches). Despite the guidelines provide information on which configurations can be used, a clear substantiation is missing. The present substantiation is brief and not connected to quantitative factors such as directional distribution or truck share. At the same time, there is a wish to update the guidelines to ensure good performance on capacity and traffic safety nowadays and in the future. This study therefore aims to provide substantiated and updated advice on applying several lane configurations in motorway splitting, for several combinations of traffic circumstances as directional distribution and truck share. The central question in this investigation is: “What is, regarding capacity and traffic safety, the best lane configuration in splitting motorways for various circumstances in the motorway network?” Various guidelines from the Netherlands and abroad were studied on which configurations they recommend for splitting motorways. A selection of configuration designs has been chosen to simulate in FOSIM, software that is specially designed to simulate traffic on Dutch motorways. For various directional distributions and truck shares, simulations were performed on the designs to determine their traffic capacity. To determine traffic safety, several safety indicators were calculated based on measured lane changes and decelerations of vehicles during the simulations. In the end, the configurations were compared to each other using these values for capacity and safety indicators, equally weighing capacity and safety. Overall truck share slightly influences the capacity of all considered configurations. The influence of directional distribution on capacity is stronger. All configurations tend to have their maximum capacity for a directional distribution such that the majority of the traffic uses the original lanes. This way, the number of lane changes seems to be lower, preventing a bottleneck on the pre-sorting section. The designs performing the best on capacity are therefore configurations with a lane addition (in other words, a non-original lane) added to the side that takes the least traffic. When the majority of traffic taking one branch becomes too large however, the branch congests, limiting the capacity of the complete section. The quality of the used safety indicators appeared to be not sufficient enough to draw reliable conclusions from. The time needed to perform enough traffic simulations for statistical significant safety results was larger than the available time for this research. Moreover, during the computation and analysis of the safety indicators, it was found that capacity and traffic safety are related more closely that initially thought, which should have been included in the safety indicators. The capacity results, that are statistically significant, form the basis of the capacity-related advice that could finetune the motorway design guidelines. It is however recommended to pay more attention to truck share in further research, in particular to truck shares that vary between the two branches. For safety-related advice, it is recommended to first investigate the possible relationship between the safety indicators and traffic capacity and compute the values of the indicators more accurately, before evaluating the total safety performance of the considered configurations. Finally, it is recommended to investigate the configuration designs on how they function in practice. Despite FOSIM is calibrated on the Dutch motorway network, a comparison between the capacity and safety findings from simulations and practice could increase the quality of the results and conclusions. |
| Item Type: | Essay (Bachelor) |
| Faculty: | ET: Engineering Technology |
| Programme: | Civil Engineering BSc (56952) |
| Link to this item: | https://purl.utwente.nl/essays/107753 |
| Export this item as: | BibTeX EndNote HTML Citation Reference Manager |
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