In the early 1990’s, with the Mariazellerbahn class 1099 locomotives approaching 90 years old, ÖBB looked for replacements to operate the service between St. Pölten and Mariazell. Finally settling on an electric multiple-unit replacement, ÖBB placed an order with SGP to provide three driving motor vehicles, three intermediate vehicles, and one driving trailer. Fitted with ELIN transmission and three-phase electrical equipment, SGP delivered the vehicles in 1994. The vehicles were numbered 4090 001-3 for the driving motors (B4hET), 7090/001-3 for the intermediate vehicles (B4hTI), and 6090.001 for the driving trailer (B4HES). All vehicles are second-class only and are fitted with Flexicoil suspension. They were formed into a four-car set, the “Mariazellerland”, and a three-car unit, the “Pielachtal”. The four-car set was to work services right through to Mariazell, whilst the three-car set was to work the Valley line services as far as the town after which it was named. Unfortunately, because of the low numbers of vehicles ordered, spare parts were not manufactured, so that any problem which stopped a unit caused the train to be taken out of service for long periods.

Wheel profiles and flat spots have been a primary cause of failure, with brakes locking regularly, causing axles to slide. One of the intermediate coaches, 7090.003, seems especially prone to this problem, and was out of service for most of 1999. Electronic breakdown has caused numerous cancellations, and seems to affect the four-car unit more than the three-car (whichever driving units are used). The four-car set has a high-voltage connection along the roofline, which means that the vehicles can not be easily separated..

In 2001 both 4090.001 and 4090.003 suffered traction motor flashover, and a decision was taken to remove the power train from 4090.003, converting it into driving trailer 6090.002. The decision was reversed, however, and 4090.003 was repaired and put back into service in Summer 2002.

Because there are no run-round facilities at St. Pölten Hbf. for narrow gauge trains, loco hauled services must be reversed the 2km from Alpenbahnhof. The EMU’s have no such problems, but are severly restricted in the number of passengers they can carry – the 4 car set has 208 seats, whilst the three car has seating for only 148. At busy periods groups of 200 or more can arrived at St.Pölten without warning – easily accomodated in a loco-hauled train (which with 2 locos can accommodate over 700 people), but impossible to take on an EMU.

The trains are 36 cm wider at the waist than a class 1099 electric locomotive, and serious concerns have been raised about emergency egress in the event of an emergency in one of the Mariazellerbahn’s many tunnels. Work was needed throughout the length of the Mariazellerbahn to provide sufficient clearance for the 4090’s, and the windows on the vehicles were altered so that it is not possible for passengers to lean out.

In order to help move the units, 1099.007 was fitted with compressed air brake equipment. The units can now work in multiple with class 5090 single-unit narrow gauge diesel railcars, so it is now possible to see a mixed-power formation on the line.

When first delivered in 1994, the units were finished in the Mariazellerbahn livery of off white with red roof panels and solebar, and mid-brown panel conatining the windows. A further red stripe connected the roof panels with the skirt under the driving cab windows, and across base of the skirting. During 1996, when out of service for repairs, all seven units were repainted, removing the brown window section and leaving a large off-white area. The red stripe at the leading edges was retained.

Models of all the vehicles are currently (6/2005) available from the Austrian firm of Stängl Modellbahn, both as a three-car and a 4-car set. Source:-