Advanced Traveler Information System (ATIS) is one of the important components of Intelligent Transportation System Architecture, and cellular probe technology is regarded as a promising detection technology for the next generation traffic data collection system. Within the recent years cellular location technology develops very fast. The accuracy of mobile location has been remarkably improved, which provides the possibility of using cellular probes to give a fairly good estimate of travel time in urban, suburban, and rural regions. This paper tries to introduce the latest progress of wireless location technology, summarize the existing simulation work and field tests in both academic field and industrial field, propose one general system architecture of cellular probe traffic system, present several critical issues in the developing of such an application system and preliminary test results from one operational system, and finally provide several suggestions and recommendations for deploying such a system.