I. Introduction
Accurate and efficient trajectory prediction for intelligent vehicles is significant in sophisticated traffic scenarios where various vehicles and human crowds travel towards respective destinations with distinctive moving patterns [1], [2]. An intelligent vehicle is expected to be capable of taking actions proactively when encountering some emergencies, such as slowing down to enable surrounding intelligent vehicles to inlet and speeding up to switch lanes for overtaking. Consequently, intelligent vehicles are required to reason about accurate future trajectories of adjacent vehicles in order to conduct risk assessments of vehicle behaviors and further take appropriate actions.