Drivers on two-way roads are sometimes allowed to enter the oncoming lanes. This happens when they are in a passing zone with a dashed yellow line. If they have room to pass safely and without breaking the speed limit, they can cross that line.
However, some drivers make clear mistakes and enter the oncoming lanes when they should not do so. This puts everyone at risk, and it can cause a serious crash. Drivers may make this mistake even when their intentions are good, inadvertently triggering an accident.
For instance, some experts who study how people tend to pass cyclists claim that "most people" will cross a double yellow line to move over for the cyclist. They're doing it to keep that cyclist safe and give them the proper space.
While that is wise, it also means that they're illegally crossing a double yellow and entering the oncoming lanes. They may think the way is clear, but what if they missed something, like a motorist who is about to turn out of a parking lot and into that lane? Or what if there is a motorcycle coming toward them, but it is small and dark-colored, so it blends into the road, and they never saw it?
If a car does enter the traffic lanes coming directly toward you, you may have very little time to react and you may not be able to avoid that crash. It is also likely to be a very violent collision due to the speed and direct impact of the cars. If you suffer injuries in such a crash, you may be able to seek compensation.