Electronic Toll Collection (ETC) systems are based on tags, on-board units associated to personal bank accounts, used for paying tolls electronically. Despite the benefits associated to their use, acknowledged by public authorities among other stakeholders, these systems are relentlessly penetrating as a means for paying the use of roads worldwide. However, governments and infrastructure operators still have a great potential to increase the effectiveness and expediency of these mechanisms. Previous literature in this field has focused on analyzing users' perceptions and willingness to pay to use toll roads. However, there is still room for addressing additional aspects such as drivers' adoption of ETC systems in these road networks allowing the payment of tolls electronically. The aim of this paper is to identify the explanatory factors influencing the adoption of ETC technologies by toll road drivers. To that end, we exploit a nationwide survey conducted to road users in interurban toll roads in Spain, and develop a multilevel logit framework to explore users' adoption and position towards the use of electronic tolling. The research concludes that drivers' tag ownership is mainly related to trip-related attributes, while personal socioeconomic characteristics play a minor role. Then, it is not possible to establish specific socioeconomic user market segments to direct policy efforts aimed at increasing the penetration of ETC. Furthermore, according to the results, delivering tag devices for free would be an effective policy measure to encourage individuals adopting electronic tolling and making additional use of toll roads, due to the benefits provided by ETC systems.