This paper proposes a multi-timescale hierarchical reinforcement learning (RL) approach to address the shortcomings of policy structure design in autonomous driving (AD). Existing RL-based AD methods often result in instability or underoptimization of driving behavior due to policies that output only short-term vehicle control commands or long-term driving objectives. In this study, we propose a hierarchical policy structure that integrates high-level and low-level policies to generate long-term driving guidance and short-term control commands, respectively. High-level policies explicitly express driving guidance as hybrid actions that capture multi-modal driving behavior and support state updates of low-level policies. Furthermore, we design a multi-timescale safety mechanism to ensure safety. Evaluation results on a multi-lane highway scenario, both simulator-based and using the HighD dataset, demonstrate that the proposed approach effectively improves driving efficiency, behavior consistency, and safety.