This is, unfortunately, incorrect. The reason the number of accidents got suddenly smaller is because people were used to markings but then they had to re-lear

This is, unfortunately, incorrect. The reason the number of accidents got suddenly smaller is because people were used to markings but then they had to re-learn how to function when the markings were removed. When you learn to drive or when you are in unfamiliar place you tend to drive slower and be more attentive. But this is only temporary effect. After some time people adjust and same problems show up. Still not convinced? What about south asian countries which tend to have little in the way of traffic signs? If lack of markings makes people behave more carefully how do you explain relative lack of safety in countries like Vietnam, Thailand, etc?