A top oil industry official says the oil and railroad industries are urging federal regulators to allow them as long as seven years to retrofit existing tank cars that transport highly volatile crude oil. The cars have ruptured and spilled oil during collisions, leading to intense fires. Jack Gerard, president of the American Petroleum Institute, said Tuesday that the institute and the Association of American Railroads are jointly asking for six to 12 months for rail tank car manufacturers to gear up to retrofit tens of thousands of cars and another three years to retrofit older cars. He said two industries also want three years after that to retrofit newer tank cars manufactured since 2011. The Transportation Department has proposed two years to retrofit older cars.