Really liked the choice and placement of the sound effects, think they both established moods and built tension well while maintaining clarity. I also loved the intonations on the voice acting, really made the characters feel alive and displayed well their attitudes, imo; also everyone was well articulated.
There was a lot of focus on the radio show at one point instead of Sam, who I see as a richer character and the intended focus (if I interpret correctly); perhaps more comments from him was a good deal? Or maybe more frequently, or maybe he reacts mid-show to something in the traffic jam, anything to keep focus on him could be good, possibly, imo.
Also, loved the "D-d-d-d-d-did you know?", hehe.
Cool stuff, a lot was left unexplained but I imagine it'll come in future episodes, naturally. I don't know the rest of the plot but I hope to listen more to the characters around Sam, like Celine or Gabe, etc, 'cause I think they can add more color without detracting the story from the character. Anyway, good job!