The "best method" is subjective as it highly depends on 1. the level of simplicity, 2. expectations and 3. technical requirements.

Render layers and post-compositing are also two drastically different and viable paths.

One potential and relatively straightforward solution that wasn't cited (or ...

Hi, is there a way in Octane to have a car inside a tunnel still reflect the HDRI environment, while also receiving shadows and reflections from the tunnel itself? Maybe by using light linking, mixing shaders, or setting the tunnel to be invisible to reflections but still visible to rays?