Models however, also have limitations. The model used for electric circuits by scientists today makes use of the idea that all substances contain electrically charged particles (see the focus idea Macroscopic versus microscopic properties).
Depending on the materials used, a driveway can be utilitarian, like gravel, asphalt, or concrete, or decorative, like stamped asphalt, stamped concrete, or cobblestone. Typical costs: A gravel driveway starts at roughly $0.75-$3 or more a square foot, or $300-$1,000 for a 12'x25' single-car driveway. Costs can double for a roadway-quality driveway. Loose gravel will need replenishing periodically, but a correctly designed, installed and maintained gravel driveway can last 50-100 years or more.
You should plan on at least 2 to 3 inches of compacted gravel. That will vary widely by region. A small 15 by 20 feet driveway with 3 inches of gravel can cost as little as $250 for a base. A longer and wider driveway or a deeper base can cost $1,000 or more.The gravel base will determine the stability of the driveway.ize Matters. The square footage -- the length of the driveway times its width -- is the key factor in paving cost. A single driveway, wide enough for one car, will usually be 9 or 10 feet wide, while a double driveway will be twice that width.