A method for determining an operational state of a driver of a vehicle uses an awareness detection arrangement. The awareness detection arrangement includes at least a first and a second source for generating data relating to the behavior of the driver. The method includes receiving, from the first and the second source, data relating to at least one of physiological data of the driver, the operation of the vehicle, and a model of the driver operating the vehicle, comparing the data from the first and the second source with a driver state model defining a plurality of predefined driver states for each of the first and the second source, respectively, determining based on the comparison, for each of the first and the second source, a state probability for each of the plurality of predefined driver states, and weighing the determined driver states for the first and the second source with each other for determining an overall operational state probability for the driver.