The most important electronic payment systems are Electronic Toll Collection (ETC) systems. They enable drivers to pay tolls automatically on a no-cash basis without stopping at toll stations. ETC systems enable transactions to be undertaken at expressway traffic speed. They are usually based on Dedicated Short Range Communication. However, some ETC systems are also based on satellite positioning and cellular communication techniques. The German TollCollect system, for example, uses GPS/GSM and DSRC as a supplement for streets where satellite positioning is likely to be too inaccurate or not possible at all, e.g. in tunnels.