okay. I'm flummoxed. Doppler effect?

also, isn't the driver on the wrong side, for you?

yes, blue shift (object travelling towards you with compressed wavelength) and red shift (object travelling away from you with elongated wavelength)

or I think it is that? It's a LONG time since I did physics A level!

and yes, the driver is on the wrong side

AHH! I remember blue shift. Thanks

lol I love it