Akinbo,
" light waves exist between the bulb and the lens of a car before hitting the air" So which 'c' do you think they are moving at. the cars? Of course. That is NOT the same c as the outside 'air's'! The difference is the car's v. The change comes as the waves are transmitted into the outside air by the glass of the lens (Maxwells near/far field transition.)
It's not an 'either or' situation with wavelength and frequency. You haven't distinguished between different observer frames. I have not suggested frequency doesn't change to an observer in the new propagation frame. Of course it does. But to measure changes between frame consistently the observer must stat y in the same frame. i.e. he CANNOT accelerate without finding different data!
Go back to the 'travelator' case, but consider standing next to the 'end' of a travellator as a line of people walking at 5kph step onto it the 'wrong' way and keep walking. You wouldn't suggest you would not see the gaps between them reduce!
THAT is the wavelength reduction (blue shift). But now consider two different observer cases. In the first you stay where you are, for a consistent understanding; You see the 'wavelength' reduce but the FREQUENCY THEY PASS YOU BY AT REMAINS THE SAME! Which is solely because the datum rest frame has changed. they still walk at 5 kph ('c').
Now jump on the travellator and stand at rest in the new frame. it is only THEN that you find the FREQUENCY has changed AS WELL AS the wavelength.
The wavelength is the real scaler quality, which changes in ALL cases. Frequency only ALSO changes if the observer CHANGES frame, to then get a REAL propagation speed which has changed from c (your original rest frame) by v (travellator speed) to the NEW local c.
You'll find the full rationale in my "Which of our assumptions are wrong" and following essays,
http://fqxi.org/community/forum/topic/1330
http://fqxi.org/community/forum/topic/1775
A very simple dynamic representation of waves moving between co-moving media is here; http://www.youtube.com/watch?v=b9KIzLuJlR0
As Einstein said;.. "...but not TOO simple..."
Best wishes
Peter