A joint order was created with SNCF and the MCR to replace the existing Z 600 transits.

Five transits were ordered in 1994 from a consortium made up of Vevey Technologies (project coordination, assembly and construction of the boxes), Adtranz (electrical equipment) and SLM Winterthur (bogies, braking and rack and pinion equipment).

For the trains be able to operate from Fayet to Martigny, they are equipped with security systems corresponding to the two lines.

Each unit is equipped with two bogies with two axles including a carrier and a motor.

The Z 800s are equipped with five braking systems: The trainsets are fitted with a Scharfenberg coupler, which allows multiple trains to couple connect together during periods of heavy usage.