The way I see it, folks who ride bicycles and motorcycles are some what similiar - we enjoy the freedom of not being in a car, but as a result, the cars have problems seeing us. In an age of cellphones, super quiet cabins, and other ways of isolating the driver from the world, I don't think even a HD's engine noise is enough to get noticed. Perhaps this is why whenever I'm riding the NH White Mountains, I got the thumbs up from motorcyclists and bicyclists alike, especially around the grim make shift crosses by the sides of the road.