Space Saver?: The Design of a Distance-Based System for Urban Environments

This article discusses a number of problems with satellite-based tolling schemes, particularly in terms of inaccuracy in certain situations. One study found that in cities, spatial determinations could be off by as much as 300 meters. The article describes a number of requisites for a fully-functioning electronic toll collection system (ETC). It must have a very high charging availability, low mischarging probability, be economical, ensure user privacy, be expandable, and flexible should new issues arise. Using an on-board unit (OBU) that communicates with the satellite system and the tolling center, a complete system also requires an algorithm to determine that the vehicle is within the specified tolling zone. With the proposed specifications in mind, the authors explain that tests will be conducted using the European Geostationary Navigation Overlay System (EGNOS) in Madrid, Spain in the fall of 2007.