Rail transportation in the United States includes freight and passenger service. Freight moves along a well integrated network of standard gauge private freight railroads that also extend into Canada and Mexico. The United States has the largest rail transport network of any country in the world, about 136,729 miles (220,044 km). A larger fraction of freight moves by rail in the United States than in most countries and freight rail companies are generally profitable.
Passenger service includes mass transit in most major American cities. Except for commuter rail, most transit systems are not connected to the national rail network. Federal Railroad Administration regulations require passenger cars used on the national rail network to be heavy and strong enough to protect riders in case of collision with freight trains.