A simple suspension bridge is an early bridge type and is still formed from native materials, chiefly grass rope, in some areas of South America. These rope bridges must of course be periodically renewed owing to the limited lifetime of the materials, and rope components are made and contributed by families as contributions to a community endevor. A more permanent variation, suitable for pedestrian and sometimes equestrian use, may be made from simple wire rope. In such bridges, the roadbed of the bridge will follow the downward and upward arc of the load bearing cables, with additional light ropes at a higher level used to form handholds. Owing to practical limitation in the grade and the response to dynamic loads of the bridge deck this type is quite restricted in its load carrying capacity relative to its span. To walk a lighter bridge of this type at a reasonable pace requires a particular gliding step, as the more normal walking step will induce traveling waves that can cause the traveler to pitch (uncomfortably) up and down or side-to-side. Such a bridge may be stabilized by additional cables that do not bear the primary structural or live loads and so may be relatively light. These also add stability in wind.