Cities are built one structure at a time. These structures can be built by private companies, by individuals, or by the government. While the structures are safe after they are built, they are quite dangerous and are accident-prone areas while they are being built. This means that the ones responsible for the structures have to warn people around them that some areas within the construction zone are dangerous and are potentially life-threatening.

The most common way of doing this is by using danger flags. This is because it is very easy to simply mark an entire area with just a few flags. Furthermore, you just can't miss the flags when they are glaringly orange. Simply noticing the color lets you realize that you shouldn't be in the same area as the flag. Otherwise, you might want to have a emergency number on the line while you're going around the construction site. These are so effective at their job that the color orange has even been associated with danger or with hazards that are often potentially life-threatening.

If you feel that the area is relatively safe except for a few specific places that have some

equipment lying about, you can use utility markers to let people know that those areas should be avoided. While it is not as dangerous as the areas with danger flags, they are still hazards that should be avoided by everyone as anyone could risk injury just by coming into contact with malfunctioning equipment. Remember that safety is at the top of the priority list when you are talking about construction sites. Disregarding that fact could cost millions in terms of damages and collateral.