Evaluation of Digital Maps for Road User Charging Applications

Advances in alternative fuel technologies and increasing motor vehicle fuel efficiency may result in a decline or flattening of demand for conventional fuels in the U.S. in the coming decades. One outcome of this development maybe a reduction in state and federal income from motor fuel taxes, the primary source of funding to maintain and improve the transportation infrastructure. To keep pace with future transportation needs, a new funding mechanism is needed to supplement or replace the current road financing mechanism. One possible approach is to charge for road use based directly on a measure of travel on public roadways using onboard computers coupled with Global Positioning Systems (GPS) and digital maps. The main goal of this research was to develop the system requirements for a digital map that is a major component of an in-vehicle road user charging system. The focus was to evaluate digital maps in the most difficult of environments – where roads of different jurisdictions and possibly different fee structures are located in close proximity to each other (a highway and a frontage road, for instance). In order for the system to be effective the onboard system must be able to place the vehicle on the correct road. Extensive testing of existing digital maps found that they are not accurate enough to be used for road user charging. There are however, new higher accuracy digital maps (not yet publicly available) that are already being used for vehicle safety applications. By combining differential GPS and such high accuracy digital maps, the ability to design a road user charging system with high geographical resolution can become a reality.