Automatische Übersetzung. Originaltext in: EN - Original anzeigen By the early 1990s, the four SBB Re 4/4^IV prototypes had completed their experimental role as test platforms for power-electronic traction. Maintenance costs for the small class had become prohibitive, prompting the Swiss Federal Railways (SBB CFF FFS) to seek a buyer.

In 1994, an agreement was reached with the Schweizerische Südostbahn (SOB)—a privately owned regional operator in eastern Switzerland—for a locomotive exchange: the SBB transferred the four Re 4/4^IV prototypes to the SOB, receiving in return four Re 4/4^III locomotives.

The exchange took place in stages:
• 10102 and 10103 were handed over on 14 December 1994,
• 10104 followed on 13 April 1995,
• 10101 completed the transfer on 23 October 1996.

At the time of the exchange, the locomotives had each covered between 1.5 and 2.1 million kilometres in SBB service.

After thorough overhauls at SOB workshops, they were renumbered Re 446 445 - 448.

Initially, all four locomotives retained their red SBB paintwork, modified with a white “SÜDOSTBAHN” inscription and a thin yellow waistline stripe. Their new owners quickly realized that the versatile, high-performance prototypes were ideal for both interregional passenger work and light freight duties across the SOB’s mountainous network.

Automatische Übersetzung. Originaltext in: EN - Original anzeigen From 1995 onward, the Re 446 fleet became the backbone of the Voralpen-Express (VAE), an InterRegio service connecting Lucerne on Lake Lucerne with Romanshorn on Lake Constance. The route crossed the scenic pre-Alpine region via Arth-Goldau, the Rothenthurm Plateau, Biberbrugg, Pfäffikon SZ, Rapperswil, Wattwil, Herisau, and St. Gallen—a demanding line with numerous gradients, curves, and tunnels that tested both traction power and adhesion.

The Re 446 locomotives initially hauled EW IV intercity coaches, later replaced by Revvivo-refurbished stock from 1999 onward. These trainsets were gradually converted to push-pull formation, with specially equipped IIId-system driving trailers compatible with the Re 446’s multiple-control electronics.

Throughout their service, the locomotives demonstrated excellent acceleration, smooth running, and reliability on both passenger and occasional freight duties.

Beyond the Voralpen-Express, the Re 446 units occasionally powered other SOB trains, such as the well-known “Gipfeli-Express” commuter service from Einsiedeln to Zürich Altstetten. They also worked postal and local freight trains between Einsiedeln, Samstagern, and Pfäffikon SZ, typically one to two round trips per week.

A reserve unit was kept at Samstagern depot, often used for evening postal trains on the SBB network.