Highways are areas where people drive cars much faster than they do when they're only going short distances. On some highways, however, there are often too many cars in the same place all at once, and the cars can't go fast at all—in fact, they go much slower than they do on other areas where cars go. A good example is I-95 in Stamford, Connecticut.
One consideration you might want to make about the danger level of highways is whether or not you are a non-human animal. If you are, you might have trouble understanding how a highway works and try to run across it. If you do, and there are cars on the highway at the time, you may be hit by one, which will likely cause your death.
If you are a human, your experience with highways will be two-fold: first, you may traverse them inside cars; second, you may be subject to the effects of putting them everywhere. If you are in a car, the danger you experience as a result of highways will largely be limited to the possibility of a car accident. These are not as frequent as you think! About 37,000 people died in car accidents in America in 2018, according to the United States National Highway Traffic Safety Administration. In the last year for which we could find Center for Disease Control statistics (2016), about 600,000 people died of cancer. So, highways are less dangerous than cancer.
The other thing that bears mentioning is that the cars that drive on highways are notorious polluters. As such, there is a connection between the prevalence of highways and the oncoming world-spanning disaster situation known as global warming.
All in all, you can get into trouble on a highway, whether you are a person or another animal, and you can get into trouble because there are highways in the first place—so we say that highways are a bit dangerous.
