The unique behaviours of drivers have many emerging applications. These include the personalization of automated/selfdriving vehicles so the owners are more comfortable with them, and the identification of changing driving behaviours that may be associated with aging or disease. This paper explores measures of driving behaviours that might allow for the differentiation of drivers based on their individual driving characteristics. An emerging challenge within longitudinal studies of drivers is to distinguish between different drivers of a shared vehicle. It also has application in the insurance industry where insurance risk and associated owner premium depends on the diversity or lack thereof of drivers for a vehicle such as a vehicle driven/never driven by secondary drivers that have higher risk driving behaviours. In this paper, a big data set of driving data for 14 older drivers is analyzed -a single year of data includes over 250,000 km and almost 5000 hours of driving for the 14 drivers. A set of 162 trip level calculated features are analyzed to determine their ability to be used to distinguish between two drivers of a vehicle. The results show that features based on road choice and driver chosen velocity provide the best performance individually and in feature pairs with 2 features providing error rates less than 5% for some driver pairs. The set of features that provided the best performance differed for each driver pair and was found to include features from measures of a driver's road choice, velocity and velocity ratio in addition to the features measuring trip similarity to two phase acceleration and deceleration relationships for the driver. The best error rate obtained was 1.5% for a driver pair. On the other hand, the results suggest that a number of features and feature groups do not allow for older driver differentiation. For instance, overnight driving and high rates of acceleration are not sufficiently exhibited by these drivers to be useful.