Mental workload is an important subject in traffic safety research, however workload measurements are expensive and time intensive. To this end a measurement method is developed which uses short video fragments of driving situations to the subject, after which they are asked about their perceived mental effort if they would be driving through those situations themselves. In this way, 32 video fragments taken from the naturalistic driving dataset are shown to 60 participants, providing information on several traffic variables, which have an effect on workload. The method managed to find significant effects for the effect of traffic density, age, weather and presence of Heavy Goods Vehicles and Vulnerable Road Users on mental workload, which can also be found in workload studies performed in the past. The method developed in this report appears to be promising as a sensitive and valid method for determining workload. However, in order to adequately attain its effectiveness, more research is needed.