Passenger seat for railway transport vehicle comprising a device for adjusting the lumbar support

The seat (1) has a backrest (3) articulated on a base (2), where the base and the backrest are guided by a structural frame. The backrest comprises a lower part (31) and an upper part (32). An articulation unit of the backrest is adapted to modify an angle formed between the lower and upper parts according to a position of the base in the frame. A lumbar support (5) is mounted on the lower part. An adjusting device adjusts depth of the lumbar support and automatically controls depth of the support according to the angle formed between the parts.