Single Vehicle Fatal accidents.

here's a couple of older links (not wikipedia ) - I'll try searching out more later -

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I did read a theory that said insects were probably responsible for some single vehicle incidents - so a bee comes into the car, either frightens the life out of you and you swerve or distracts you enough to cause an accident, after the accident the bee flies off and no one ever knows what happened.
 
Accidents just happen sometimes.

A few fridays ago I was driving on a main road that links two cities. I was behind a 08 car and we both were behind a truck doing about 80km/h. The conditions were wet. We were on a perfectly stairght road. The road margin is about 4" from surface of tarmac to soft margin, the yellow broken line is on the verge of the road,I.E if you are on the yellow line half your tire is off the road.

08 car infront of me slightly goes off verge and when driver tried to correct, the car spun around 360 a few times, entering otherside of road (Thank God, nothing was coming) and coming back to my side and flipping into ditch. It was really dramatic. When I got to the car it was completely off the road and wedged on it's side at 45 degrees. I had to climb onto back passenger door to open drivers door. Thankfully the two ladies inside were unhurt.

I was amazed how it just happened out of nowhere.
 

Soft margins on the poorer intercity routes have caused many accidents IMHO.

The N5 in Roscommon was lethal for this. The section from Tulsk to Frenchpark particularly bad. I've seen a truck in front of me get caught in a soft margin and nearly cause a head-on collision. It could also have caused a major single vehicle accident. It was doing well under the speed limit!
 
It's a soft bit at the side of the road, adjoining the tarmacadam of the road..ie, mud quite often.
In some roads, there is very little space between the driving part of the road, and the edge of the road (often signposted by a yellow roadsign picture of a car falling off the road)

Nicola