Hi Zaph,
That's a toughie, because it depends on the buyer's opinion/intent. Bear in mind, you're referring to a busy road, not a main road. There can be a world of difference between the two. Just because it is a main road doesn't mean it will have heavier traffic than one of its alternate routes. This is why it's important to be on the ground, and look to see what is around (as it seems you've done) and how it fares at different times of the day. What is parking like during peak hours? Are there "no standing" zones, children's crossings etc? If so, how will its accessibility affect you/your potential tenants?
Personally as an investor, I have no issue with buying on a main road, provided there is no obstruction to the entry point onto the property. In other words, as long as you can safely drive into/out of the property without being rammed by an 18-wheeler screaming down behind you whilst you're sitting there patiently waiting to turn into the driveway; I'd consider it.
I've lived, bought and sold (for a handsome profit) on main roads, and (albeit a light sleeper) I don't mind the noise factor. Some people do, and think their tenants will also mind, hence they don't purchase on these roads. It is especially handy though if transport (ie. bus, tram) constitutes part of the everyday traffic, as that can add to the value of the property.
Main roads can be cheaper because often people assume they will be heavily trafficked, but this is not always the case.
Busy roads don't bother some people, and in fact, if they are within walking distance to nearby amenities such as schools, shops, transport etc, they can sell at a premium regardless of the traffic they attract.
