In 2005, our leading cycling enthusiast at work was killed cycling in one morning, pulling out of a side junction into the path of a (non-speeding) car on the main road. It was a hell of a shock for all of us - he was a really nice guy and had been cycling for many, many years.
The accident was well-witnessed and took place on a section of road with good visibility. It seems he was just cycling on auto-pilot and simply hadn't taken in that a car was coming. One possible factor was that he was likely to have been listening to music as his headphones and player were found in the road.
He clearly didn't see the car or take it in. Whether hearing the car would have made a difference, I'll never know but to deprive yourself of a sense that can give you additional warning seems in hindsight such an easy thing to avoid.
John