The aim of this study was to study the possible effects an active accelerator pedal will have on the driver's behaviour, that is, how the test-persons adapt their driving to the system after long time use, apart from the possible effect it will have on their speed-choice. Variables such as interaction with other road users, conflicts, speed adaptation in low speed situations, distance to vehicle in front, yielding-behaviour etc. were studied. In order to be able to study the variables above a method called In-car observations or Wiener Fahrprobe was used. Two observers rode along with the test-person on a specified route. In addition an instrumented vehicle was used. In total 28 persons were observed driving without the active accelerator pedal and driving with it after long time use.