I. Introduction
Vehicle speed prediction has essential theoretical value and widespread applications for intelligent vehicles. The pre-known future velocity can significantly reduce energy consumption and emissions of vehicle propulsion systems [1], [2], better understand the traffic environment for advanced driver assistance systems [3]–[5], and improve the battery lifetime and available mileages of electric vehicles [6]. Motivated by these above, existing studies have developed various speed forecasting approaches using different information. However, accurate on-road vehicle speed prediction is still challenging due to the influence of many factors such as traffic condition, vehicle type, and driver behavior [7].