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
Phrase in terms of a universal schema, the X-bar schema, which sees each head as projecting at least three levels of structure: a minimal level, an intermediate level, and a maximal level. Thus an individual noun (N), such as "Susan" in "Susan laughed", will project up to an intermediate level (N') and a maximal level (NP, noun phrase), which means that "Susan" qualifies as a phrase. (The subject slot in the sentence is required to be filled by an NP, so regardless of whether the subject is a multi-word unit like "the tall woman", or a single word performing the same