Roads in the three main biomes are different from one other. The Main Biome's roads have the pebble material, and are light-grey in color. The Safari's roads, however, are made out of the Concrete material, and are light-grey in color. And lastly, the Tropics, which has a black road.
Roads are generally straight, never curving smoothly. They sit at the top of the ground by about 0.2 of a stud. Occasionally, Spook Wood can spawn on a road. Spook Wood cannot grow on Safari roads because the Roads are labeled "Read"; that caused a typographical error.