Could you save the same amount of time by modernising the existing lines?
Toulouse–Dax link
This rail link between the two areas, which does not currently exist, will make the South West more accessible and save a considerable amount of time, especially compared to road transport. In a second phase, it will connect the two South West metropolises to Spain and Portugal, thus completing the North–South Atlantic Corridor and the Atlantic–Mediterranean West–East link.
Several scenarios have been studied for the modernisation of the existing line between Bordeaux and Toulouse. The possible time saving is less than 10 minutes on the current route. By comparison, the new line project would save between 49 and 56 minutes (with and without stops). This time saving would reduce the journey between Paris and Toulouse to three hours and 10 minutes. There is therefore a difference of 45 minutes between the construction of the new line and the proposal to increase the speed of the existing line by modernising it.
Another modernisation scenario achieves a time saving of 27 minutes, but requires the construction of 50 km of new sections of lines and additional tracks between Bordeaux and Langon and between Montauban and Toulouse. For twice the time saving, this would cost almost as much as a new line, with a major impact in a highly urbanised area and very long construction times. The line would have to be closed for several years, or partially closed for many more, to carry out the work on the line used. In this case, journey times would be considerably longer, as speeds would be reduced and traffic would probably be diverted to the motorway.
Bordeaux–Dax link
A high-speed line saves five minutes compared to increasing the speed to 220 km/h by upgrading the track, but upgrading reduces the capacity of the line and does not allow the development of freight or daily regional trains.
What’s more, increasing the speed costs as much as building a new line from Captieux to Dax, although it offers fewer services: less increase in capacity, no connection between Mont-de-Marsan and the high-speed network (which would not put the capital of Landes within half an hour of Bordeaux), not to mention the difficulties and disruptions caused by the works that would have to be carried out while trains were running.
Sources: Updated summary of the alternative modernisation of existing lines, SNCF Réseau, November 2021.