Perhaps I will have to revisit the camera settings originally specified. There is certainly scope to use a higher exposure value while still being able to render low amounts of ambient light as darkness. When I originally tested it out, I used a 36W LED light source, so might have over estimated the typical light output of a more 'average' bike light. I'll take another look at this tonight once it is dark outside.
Soundwave, do you know the wattage (power consumption) of that bike light?