Wooden ramps are dangerous in a variety of ways. Wood, unlike steel or concrete, may deteriorate over time and may cave in. If the ramp is positioned outside, wood absorbs moisture and might become particularly slippery after a storm. To improve traction, wooden ramps should be covered with a slip-resistant paint or other coating. The same goes for metal ramps; if not painted, they will rust over time. There are also safety concerns with ramps that have sharp edges or holes. These can cause injuries if someone trips over the edge of the ramp or hits their head when climbing up it. The ramp might also be the source of a fall if it is wet or icy where it meets the ground. The hole in itself is also a problem because it makes it harder to climb up/down the ramp. People who use a wheelchair are especially vulnerable while using a ramp. There are three types of ramps: horizontal, vertical, and hybrid. A horizontal ramp is one that rises straight up from the ground at an angle. This is the most accessible type of ramp but also the most dangerous. Someone using a wheelchair could roll back down the ramp if they lost their balance. A vertical ramp rises straight up from the ground without any angle. It's the safest type of ramp but also the least convenient because you cannot drive a vehicle up it. A hybrid ramp is half-vertical and half-horizontal.