From the cab - a HGV drivers view

How about looking around and noticing what is around you?

You miss my point. I am not talking about the dangers (or not) or not hearing things around you. I am talking about concentration. Human brains are not good at multi-tasking. When listening to music, that will occupy at least some of the brain. Consciously looking around is one thing, but the ability to react quickly to things that happen in periphary vision are another. Being deeply lost in thought, or enjoying the surging crescendo of Wagner's Ride of the Valkyries will diminish your reaction times. Personally I like my music loud enough to force my attention, otherwise it is just some annoying background noise, so I won't wear headphones ever.

I would hope the people here who do listen to music while cycling are not becoming deeply involved in listening, but some music is designed to draw you in, and demand your attention. Try doing a crossword puzzle while listening to heavy duty Gabber.

Denying yourself the sense of hearing is one thing, but denying yourself the abilty to react quickly is quite another.

(I am sure many cyclists who listen to music have sensible playlists at sensible volumes, but I raise this as it seems to have been somewhat overlooked in the discussions I have read so far on this matter. Maybe I get a little more mentally involved in my music pleasure than most)

http://www.highbeam.com/doc/1G1-18321470.html

http://www.drdriving.org/misc/music_strick_report.html

http://www.lowertheboom.org/links/h10_reaction_time.html