Your awareness of anything else is not so much non-existent but diffuse. By that, I mean you are aware to the bare extent necessary of, for example, passing motor vehicles, the occasion siren or bird noise, but you do not direct the focus of your attention and awareness to those sorts of things. On the contrary, you remain fixed and focused on such things as the act and pattern of your running, the sensations engendered by your running (for example, your posture, your heart rate, heartbeat, the pattern of your breathing, the sensation of your feet hitting the ground one at a time, and so on), and the feel of the surface upon which you are running include its flatness or steepness as the case may be. You are aware of the hill that you are climbing, of the various little holes in the road surface, of the driveways you cross over, and so on. In other words, you are fully present while you run.
I do not listen to music or an audiobook when I am running, although I am aware that many do. You cannot do two things at once. Forget all about so-called ‘multitasking’, for there is no such thing. There is only ‘switch-tasking’, that is, toggling from one task to the other. Follow the advice of Saint Paul who said, ‘This one thing I do’ (Phil 3:13 [KJV]). Zen says the same thing. When you’re washing the dishes, just wash the dishes. Do nothing else. Think of nothing else. Just wash the dishes. Ditto when you’re running. Just run—with choiceless awareness of what is happening inside of you both psychologically and physiologically. You have enough to do just doing that. So, my strong advice is—get rid of as many external distractions as you can. That way you can focus on the activity of running and the sensations engendered by that activity.