We see thousands and thousands of these. Whilst I appreciate that speed can be a contributory factor in accidents, I would need to ask this.
How far down the main road is visible from your position? Do you have the location details as I would love to see this on Google Local.
I would suggest that if you did not see the other vehicle approaching due to it's speed, then the road must be on a very sharp corner, as if it was a fairly straight road, then unless the other car was touching 100, I fail to see how people cannot notice oncoming traffic. If the other vehicle was exceeding the limit (which I assume to be about 30 as it's most likely a built up area), then your car must have been in a hell of a state, and the police would have known that it couldn;t have been your fault.
Sorry to sound so negative here, but far too many people rely on ''the other person was speeding'' excuse rather than simply admitting that the though they had enough time to pull out or simply didn't pay enough attention to the road.