Separating traffic flows: when and how?

It needs to be noted that there is not one definition for unbundling (separation of traffic flows). However, the main principle of separating traffic flows is that flows do not intersect and therefore at least one of the flows can retain its level of service. In situations where traffic flows intersect, it is possibe that capacity drops or dangerous situations occur due to differences in speed. These are also the main reasons for applying unbundling.

Many reports focus on one specific way of unbundling; collector-distributor lanes, express lanes, bus lanes, freight traffic lanes or bicycle paths. These all are examples of unbundling within different network levels. Unbundling has been applied in the Netherlands several times, but isn’t working as hoped for in all situations. Because of this reason and the uncertainties within the term unbundling, this research focuses on when and how to apply unbundling.

The main aim of this research is to generate a general tool, a decision tree, which can help to decide if unbundling is an efficient/effective measure to take into account during the exploration phase (of possible solutions). If unbundling should be considered as an option, the tool also gives directions on how to apply unbundling. In order to do this, ‘standard situations’ (archetypes) will be defined. For each of these archetypes, the best way of unbundling will be investigated by simulations.

The research mainly deals with the unbundling of higher road network levels, namely through and local traffic on motorways. In the case of motorways, the aim is to have
through traffic unhindered by traffic that is entering and exiting the motorway and, therefore, having at least through traffic retaining its level of service. Problems between through and local traffic occur mainly because these traffic flows of different network levels are using the same infrastructure.

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