Myself and another party are having a discussion as to wether or not
merely listening to the radio while driving is a distraction. I think
that listening to a radio or cd player while driving is not
distracting as long as one is not adjusting the controls while in
motion and as long as the sound is no louder than normal conversation
tones. Although I am fairly certain this is true, I cannot find any
scientific evidence to back it up. Could you please give me reliable
sources and studies that prove that driving with the radio on as a new
driver is not a distraction as long as adjusting it and excessive
volumes are avoided. Thank you.

Some studies may come to the conclusion you wish. My guess is radio
and cell phones are a minor distraction for most drivers, and new
drivers need to give the driving their full attention. Selected
drivers will be safer with the radio on, but this is a minority in my
opinion. I occasionally listen to Rush Limbaugh, Neil Bortz or Michael
Savage while I drive. I'm sure I am occasionally distracted, but
boredom or other thinking can also be distracting. The content of the
broadcast also makes a difference. I'm least distracted by music
written about 1946 or earlier. Also, it is not realistic to think you
won't be adjusting the knobs and buttons while in motion.   Neil

You might want to take a look at this study (and others found here):

http://nhtsa.gov/portal/site/nhtsa/template.MAXIMIZE/menuitem.416f74e8613992381601031046108a0c/?javax.portlet.tpst=4427b997caacf504a8bdba101891ef9a_ws_MX&javax.portlet.prp_4427b997caacf504a8bdba101891ef9a_viewID=detail_view&javax.portlet.begCacheTok=token&javax.portlet.endCacheTok=token&itemID=71052f9b8559a010VgnVCM1000002c567798RCRD&viewType=standard

As radio listening is not explicitly mentioned, you could probably
claim that as some evidence for your position.

I hope this helps.

Have a good day.