In this paper, we present a comparison of the Samsung Galaxy S™ [20], the Motorola Droid X™ [3], and the iPhone 4™ [2] using the real-time vehicle tracking application FreeSim_Mobile [1,19]. Using the built-in GPS receiver and the web capabilities of these smart phones, coupled with a V2I architecture, we are able to send a continuous flow of speed and location data to a central server for processing by FreeSim [13-15], a real-time traffic simulator. The proportional model algorithm [17] is

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... used on this data to determine the time to traverse a section of roadway in order to report in real-time the current flow of traffic. At the University of Alaska Anchorage, we currently have vehicle tracking devices installed in 80 probe vehicles that traverse the Anchorage area. In addition there is a small test fleet of probe vehicles using the iPhone 4 [1,2,19]. In this paper we analyze the capability of two different Android-based [18] phones, the Samsung Galaxy S and the Motorola Droid X, on reporting accurate and reliable locations and compare them to a vehicle tracking device as well as the iPhone 4, which has been shown to be as accurate as a vehicle tracking device [1,19]. Drivers equipped with a Samsung Galaxy S, Motorola Droid X, iPhone 4, and vehicle tracking device manually timed how long it took to travel along a 0.98 mile/1.58 kilometer section of roadway. From this location and speed data reported by each device, the amount of time to traverse the test section of roadway was determined using the proportional model algorithm [17] and compared to the actual amount of time it took to traverse the test section of roadway as manually timed. The results of the vehicle tracking device had an average error factor of 0.79% from the actual time to traverse the section of roadway, whereas the Samsung Galaxy S was 4.59%, the Motorola Droid X was 0.84%, and the iPhone 4 was found to have an error factor of 0.60%. We conclude that the iPhone 4 and Motorola Droid X have higher accuracy than a vehicle tracking device.