ITU‐T's Technical Reports and Specifications 303 Europe. The advantage of electronic payment is the fact that the vehicle does not need to stop, thus avoiding traffic jams, besides the fact that it is not necessary to carry money. In this way, it is possible to provide greater customer satisfaction and a reduction of human resource costs to the operator, among other advantages. Typically, a tele‐toll system is based on short range microwave technology designed for the purpose, known as Dedicated Short Range Communications (DSRC). However, for the majority of European highway concession holders the systems are incompatible with each other, given that the initial standard only served as a Recommendation for the system. Hence each operator installs it in accordance with the application sought. The majority of these systems are based on the Low Data Rate (LDR) sub‐standard, given that this was the first standard created. The incompatibility raises some difficulties for car drivers, who (sometimes inside the same area), have to affix several identifiers in their vehicle if they wish to use various systems. With the increase in traffic on European roads, the problem of interoperability between country systems/operators takes on greater importance. With a view to resolving this problem, the Medium Data Rate (MDR) sub‐standard was devised, aiming at providing interoperability between countries and systems. Nowadays, DSRC technology is not used exclusively for the electronic payment of tolls, for it is starting to have other applications, such as payment at parking lots and fuel stations, or even simply for controlling the access of vehicles. This system implies the need for toll barriers (access points), where the vehicle makes the transactions. Figure 62 – Diagram of the operation of the toll payment systems on highways Source: European Patent Application EP 1944736 A1 Communication through short range radio based on microwaves (9) is regulated by the DSRC standard, which is currently used in tele‐toll systems (4). There are three sub‐standards in the DSRC, which are LDR, MDR and HDR (High Data Rate). LDR merely contains recommendations, having no obligatory character. On the other hand, MDR, was developed in order to guarantee greater interoperability between systems. HDR was devised to permit communication between vehicles. The MDR sub‐standard is the one adopted in this invention, consisting of three layers which have a message/protocol stack specific for carrying out transactions.