This article describes the implementation and experimental results of a real-time carrier phase differential global positioning system (GPS) aided inertial navigation system (INS). The implementation is the result of a study to analyze the capabilities of such a system relative to the requirements of advanced vehicle control and safety systems (AVCSS) for intelligent transportation systems. Such navigation systems have many application possibilities (e.g., aviation and precision flight, automated mining, precision farming, dredging, satellite attitude control). Advantages and disadvantages of the GPS, INS, and differential GPS-aided INS approaches are discussed. The implementation achieves 100-Hz vehicle state estimates with position accuracies at the centimeter level through the use of differential carrier phase GPS techniques.