A 12'x25' single-car gravel driveway costs $300 to $900 to install 4" to 8" deep, and a double-car runs $600 to $1,800. Adding a 12' wide road a quarter-mile long costs $15,000 to $60,000. When extending your existing driveway, material costs for sand, gravel, paver stones, and edging are $750 to $800 for building an addition of 5' x 20'. Start