Single Fam House on Busy Road - Impact on Retail Value and Hold Time?

[Brian Brigham]

Looking at a nice lot, where the front of the house and driveway are on a private street, but one side of the property is along a somewhat busy 2 lane road (one lane each direction).  Its a large lot and the house is pretty far from the street (I'd sat 60-80 feet, maybe more).  I would like to consider this for a flip, but I know the main road will of course reduce retail value and make the property more difficult to market.

Do others have a general rule of thumb about the percentage decrease in value and the increase in hold time that a main road may have on a property?  

Thanks