The Ring Never Relieves – Response rules for metro circle lines

Regarding the disposition of metro lines in order to recover from delays, in the literature there can be found two branches of contributions: descriptions of response rules such as expressing (aka skip stop), holding and short-turning together with case studies of their application. And there are fully-automated optimization models that optimize some specified objective function, e.g. minimizing the total train delays.

We are not aware of any study that puts its focus specifically on ring lines (aka circle or loop lines). In the absence in particular of essentially immediate time buffers in turnaround activities in the endpoints, the operation of a circle line is particularly challenging, when comparing it with the common bi-directional lines.

In this spirit, we are collecting response rules that are applicable especially for circle lines. We sketch their impacts on the passengers’ travel experience and on the resource schedules for the rolling stock and staff, and we provide illustrative drawings.

Moreover, we conducted interviews with experts of eleven metro networks that are operating circle lines. We report their answers, which response rules are applied most often. Despite the limited possibilities along circle lines there is a broad repertoire of response action that is taken regularly – somehow surprisingly, one standard general response rule that is often discussed in the literature and in principle applicable to circle lines, too (expressing), is almost never applied in practice.