This is the pre-print version of the accepted article. For citation, please use:Khattak, Asad, and Behram Wali. "Analysis of volatility in driving regimes extracted from basic safety messages transmitted between connected vehicles.Abstract -Driving volatility captures the extent of speed variations when a vehicle is being driven. Extreme longitudinal variations signify hard acceleration or braking.Warnings and alerts given to drivers can reduce such volatility potentially improving safety, energy use, and emissions. This study develops a fundamental understanding of instantaneous driving decisions, needed for hazard anticipation and notification systems, and distinguishes normal from anomalous driving. In this study, driving task is divided into distinct yet unobserved regimes. The research issue is to characterize and quantify these regimes in typical driving cycles and the associated volatility of each regime, explore when the regimes change and the key correlates associated with each regime. Using Basic Safety Message (BSM) data from the Safety Pilot Model Deployment in Ann Arbor, Michigan, two-and three-regime Dynamic Markov switching models are estimated for several trips undertaken on various roadway types. While thousands of instrumented vehicles with vehicle to vehicle (V2V) and vehicle to infrastructure (V2I) communication systems are being tested, nearly 1.4 million records of BSMs, from 184 trips undertaken by 71 instrumented vehicles are analyzed in this study. Then even more detailed analysis of 43 randomly chosen trips (N = 714,340 BSM records) that were undertaken on various roadway types is conducted. The results indicate that acceleration and deceleration are two distinct regimes, and as compared to acceleration, drivers decelerate at higher rates, and braking is significantly more volatile than acceleration. Different correlations of the two regimes with instantaneous driving contexts are explored. With a more generic threeregime model specification, the results reveal high-rate acceleration, high-rate deceleration, and cruise/constant as the three distinct regimes that characterize a typical driving cycle. Moreover, given in a high-rate regime, drivers' on-average tend to decelerate Keywords: connected vehicle, basic safety messages, instantaneous driving decisions, driving regimes, Markov-switching dynamic regressions.As a part of U.S. Department of Transportation's (USDOT) Real-Time Data Capture and Management Program, Safety Pilot Model Deployment (SPMD) in Ann Arbor, Michigan features real-world demonstration of connected vehicle safety applications, technologies, and systems by hosting approximately 3,000 vehicles instrumented with V2V and V2I communication systems (Henclewood, 2014). Altogether, 75 miles of roadway in Ann Arbor, Michigan are instrumented with roadside equipment (RSE) that are capable of communicating with appropriately instrumented vehicles, and devices via advanced communication and sensor technologies such as dedicated short-range communications (DSRC) (Henclewood, 2014...