Are Smartphones Viable for the V2X Transition? A Platoon-Perspective Stability Analysis under Real-World Errors

The benefits of vehicle-to-everything (V2X) systems remain limited by the large stock of conventional vehicles, low penetration, and high retrofit cost. From a platoon perspective, this paper evaluates smartphones as low-cost transitional V2X terminals. Because data accuracy is the main barrier to large-scale smartphone use, we collected 12 h of onboard reference data and 72 h of smartphone observations across three road scenarios, three smartphone vendors, and two device generations. We then analyzed the statistical characteristics of smartphone GNSS speed errors. The errors were well described by a three-component Laplace mixture model. Their main body consisted of two small-magnitude components and was accompanied by low-probability heavy-tailed errors. Based on the measured error characteristics, we developed a linear stochastic platoon dynamics model for connected human-driven vehicles (CHVs) and derived mean-square stability conditions to evaluate the stability applicability boundary of low-cost V2X. The results show that the current measured error parameters retain a good stability margin over the common driving speed range, and the occurrence probability and scale of the heavy-tailed component are the main factors affecting the strict mean-square stability boundary. Monte Carlo simulations further show that, under empirical full mixture errors, the average improvement in stability performance relative to the human-driven vehicle baseline reaches 75.84%, whereas the degradation relative to the ideal CHV case is only 1.79%. These results indicate that smartphones used as V2X terminals have the potential to improve platoon stability through vehicle state sharing. They provide a quantitative basis for transitional V2X deployment among existing vehicles.