Introduction
The ubiquitous parking meter stands silent guard on sidewalks throughout major cities worldwide. The parking meter not only collects money from constituents to be used for various traffic-related purposes, but also serves as a parking regulator during the busy daytime hours. It helps insure that popular parking spots circulate users throughout the day. In Cambridge alone, there are thousands of parking meters.

The parking meter is an almost omnipresent device designed for public interaction. The parking meter has several functional requirements, which have been addressed in different ways from time to time and place to place. |