Alley may be paved, or unpaved, and a blind alley is a cul-de-sac. Modern urban developments may also provide a service road to allow for waste collection, or rear access for fire engines and parking. Because of geography, steps (stairs) are the predominant form of alley in hilly cities and towns. This includes Quebec City in Canada and in the United States Pittsburgh (see Steps of Pittsburgh), Cincinnati (see Steps of Cincinnati), Minneapolis, Seattle, and San Francisco as well as Hong Kong, Genoa and Rome. Some alleys are roofed because they are within buildings, such as the traboules of Lyon, or
Carroll Alley postulated that the correct understanding of the lunar laser ranging measurements, the behavior of clocks in a global positioning system, and many strong gravity field astrophysical phenomena—such as gravitational radiation—require the interactive N-body solutions of the Yilmaz Theory (or "New Theory"), which are not present in Einstein’s General Relativity field equations. Alley maintained the and remained active in the study of gravitation until his death. Carroll O. Alley, Jr. was born in Richmond, VA to Carroll Overton Alley, Sr. and Mittie Points Alley on June 13, 1927. Alley attended John Marshall High School, where he was a swimmer, choir member,