Street materials may play a significant role in determining the practicality of the road. Rural sidewalks may be paved in rougher porous materials, such as gravel or limestone, to allow water movement. To assist in the growth of street trees, urban roads should use permeable materials, allowing water to reach the roots. Suburban areas should retain the growth of green space, with a sequence of tree planters allowing for rain gardens and other natural features. For the most benefit, local materials should be emphasized, such as limestone in South Florida.