Aging accidents

At some point, while driving from Khartoum to Kosti, I saw a bus lying on its side in de sand next to the road. I was a bit shocked to see such obvious results of a traffic accident and I asked our driver what had happened. He said that the bus had hit another car, which I saw lying on its side a bit further alongside the road. “Some of the people who died in that accident”, he continued, “were buried straight away”. He pointed at a couple of small sandy hills close to the bus. A bit overwhelmed by the feeling that this deadly accident had probably recently happened on the same road we were driving on, I asked our driver when the accident took place exactly. His answer was short and rather unexpected:  “Two years ago”.