During the 1960s NSB realized that they would need a new generation of electric multiple units for local traffic.

Both the Class 65, 67 and 68 had for thirty years been built with slight modifications, and NSB needed both new and more modern trains for their operations.

NSB decided on a number of rationalizations, first of all a new interior so that two new cars could hold the same capacity as three units from the older models.

For instance on the line from Oslo East Station to Ski this allowed NSB to reduce the number of operative car from nine to four.

This allowed somewhat more flexibility, and NSB kept the A- and B-series as twin-cars so they could combine trains to make any number of cars needed between two and nine.