"Blue Arrow" BCFe 4/6 # 736 of the BLS foundation is entering Chambrelien, a switchback station, coming down the 2.7 % grade from La Chaux-de-Fonds. This iconic vehicle from 1938 ran a birthday party train on this wonderful summer day, from Olten via Solothurn-Biel-Sonceboz-La Chaux-de-Fonds-Le Locle-La Chaux-de-Fonds-Chambrelien-Neuchatel-Biel-Solothurn-Olten.