Most traffic accidents occur on **straight roads**. This is because, although curves may seem more dangerous, straight roads often give a false sense of security. On these roads, drivers tend to relax more, which can lead to distractions and not being as attentive to traffic or road conditions. Additionally, on straight roads, vehicles tend to reach higher speeds, which increases the risk of serious accidents.

On the other hand, although highways and expressways are types of roads where high speeds are allowed, they have fewer accidents compared to other roads. This is because they are designed to be safer, with wide lanes and no level intersections. However, on straight sections of conventional roads, the lack of these safety features can contribute to a higher number of accidents.

In summary, straight roads are places where accidents are more frequent due to the combination of speed, distraction, and a lower perception of risk.