In theory bone-conduction phones would allow more ambient sound. But I've been happy with one earbud in my curbside ear. But another big factor in hearing and perceiving the surrounding environment is limiting the audio content to spoken-word.

In my personal, non-scientific experience, it seems easier to perceive and separate ambient sound, like traffic, from spoken word contend, than from more abstract sounds as found in music. BAck when I listened moAnd of course volume level matters as well. And keeping one ear "free" helps.

With one earbud I still seem to be able to locate sounds around me.

Also, I've found interview, conversation or round-table podcasts work better for me than narration, especially audio books. In live conversation, speakers optimally will make sure they are being understood, adding repetitions, rephrasings, helper words and helper phrases and other conversational devices that monologists sometimes overlook, and are considered extraneous in written pieces since readers can rescan previous sentences, etc. I cannot enjoy audio books if I can't rewind, or skip around.

However, when I drive, music seems like less of a hinderance, since driving with the windows up tends to significantly mute most traffic cues except horns and louder vehicles.