In order to investigate the need and to define priorities of investments in the improvement of the traffic flow in Northern France a trajectory study and a traffic flow study are being executed for the ECMT class Va network of Nord-Pas-the-Calais. The named Canal à Grand Gabarit links the Port of Dunkerque with the Scheldt River and its connections with the navigable waterways of Wallonia (Belgium) in a west east direction. In a south-north direction it will link the future Canal Seine Nord Europe with the Deûle-Lys river connection, and will as such provide a high performing inland waterway connection between the Seine basin (France) and the ports of the Western Scheldt and further on Rotterdam (Belgium-Netherlands). To accommodate the expected increase in traffic, potential bottlenecks will have to be identified, and improvements investigated and proposed.
The trajectory analysis allows to study the geometrical constraints to navigation, and their impact on safety, ease and fluency of the traffic on a case by case evaluation, in which the interaction between ships, or between ships and the waterway infrastructure is investigated. The required space between ships, and between ships and infrastructure can be defined for different ease, safety or fluency categories of the waterway. Such analysis will however not allow to define the viability of the waterway network to accommodate the traffic. For this purpose a traffic model is used, the latter will however be fed with the nautical intelligence of the trajectory analysis.
A desk top analysis is used to test the existing and design canals, and their ease and safety level. Sections with the lowest ease levels can as such be identified, as well as critical sections for overtaking and encountering other ships. These are the prime objectives for real time navigation simulations that are used to define the functional constraints of the different waterway sections. Viability and conditions of ship-ship and ship-infrastructure encounters can be defined through these simulation: speed, required space (length and width), possible ship (class) combination, for different equipment, flow conditions, … This information is used to both propose and investigate measures for improvement of the infrastructures or canal, or to either accept a lower functionality and impose restrictions to the navigation (e.g. reduced speed, alternating traffic …). To understand the effect of traffic fluency of such a decision, however, a traffic model is used.
A traffic model allows to build up an image of the traffic flow for a given traffic density in a given network with its given geometric characteristics. With increasing density the flow will at first increase linearly, but will reach a maximum for a specific density, after which flow decreases again, and finally comes to a standstill.
The traffic model will be used as an instrument to identify bottlenecks for the traffic flow for expected traffic after the construction of the Canal Seine Nord Europe, and to support well balanced decisions for both structural and soft measures to accommodate the expected traffic flow. It is worth to investigate whether investments in enlargement of the waterway are useful, if lock capacity remains unchanged, and whether the effort should be put in the upgrading of the lock complexes or in the bottle necks of the canal proper.
The existing traffic model IMDC Waterways (Adams et al., 2014), has been improved to include berthing times at intermediate destinations such as quays, and to take into account temporary constrictions of the fairway due to ships being (un)loaded. Speed or alternating traffic is either imposed (regulations) or calculated on the basis of ship characteristics.
The model is a so called hybrid traffic model combining theory from both microscopic as macroscopic traffic models, to allow a reduction of calculation time compared to pure microscopic models. The handling of ships is on an individual level (microscopic), checking the ship by ship. It is macroscopic in the sense that stretches with similar geometric characteristic are defined as single links characterized by the most constraining cross section. Links are defined to handle the traffic in a realistic way, without compromising calculation time. Traffic is generated based on an Erlang distribution law, which may vary in function of the traffic density at any given time (variation during the day, during the week – largely due to operating times of the locks). After a warming up period an image of the traffic is built. Allowing to evaluate the traffic capacity of the waterway network including locks, quays, ports and waterway sections. Calibration is based on known traffic flows.
Knowledge from the real time simulations of the trajectory analysis is used in the traffic model: to limit ship speed in critical sections during encounters or overtaking manoeuvres, to define required space for the manoeuvers by specific ship classes, and to check whether the manoeuvers are possible or whether traffic must alternate. The insights from the traffic model flow back to the definition of measures to be investigated by the real time simulations.
The presentation will focus on the interaction between the trajectory study and the traffic study, and the proven benefits for both of the studies.