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Pedestrian conflicu and lane obstructions created by stopping or standing buses, trucks and parking vehicles that cause turbulence in the traffic flow are typical of downtown streeu. The speed of vehicles on urban streeu is influenced by three main factors, street environment, interaction among vehicles and traffic control. As a result, these factors also affect quality of service. The street environment includes the geometric characteristics of the facility, the characxer of roadside activity and adjacent land uses. Thus, the environment reflecu the number and width of lanes, type of median, driveway density, spacing between signalized intersections, existence of parking, level of pedestrian activity and speed limit. The interaction among vehicles is determined by traffic density, the propottion of trucks and buses, and turning movemenu. This interaction affecu the operation of vehicles at intersections and, to a lesser extent, between signals. Traffic control (including signals and signs) forces a portion of all vehicles to slow or stop. The delays and speed changes caused by traffic control devices reduce vehicle speeds, however, such controls are needed to establish right-of-way. The average travel speed for through vehicles along an urban street is the determinant of the operating LOS. The travel speed along a segment, settion or entire length of an urban street is dependent on the running speed between signalized intersections and the amount of control delay incurred at signalized intersections. LOS A describes primarily free-flow operations. Vehicles are complexely unimpeded in their ability to maneuver within the traffic stream. Control delay at signalized intersections is minimal. LOS B describes reasonably unimpeded operations. The ability to maneuver within the traffic stream is only slightly restricted, and control delays at signalized intersections are not significant. LOS C describes stable operations, however, ability to maneuver and change lanes in midblock location may be more restricted than at LOS B. Longer queues, adverse signal coordination, or both may contribute to lower travel speeds. LOS D borders on a range in which in which small increases in flow may cause substantial increases in delay and decreases in travel speed. LOS D may be due to adverse signal progression, inappropriate signal timing, high volumes, or a combination of these factors. LOS E is characterized by significant delays and lower travel speeds. Such operaxions are caused by a combination of adverse progression, high signal density, high volumes, extensive delays at critical intersections, and inappropriate signal timing. LOS F is characterized by urban street flow at extremely low speeds. Intersection congestion is likely at critical signalized locations, with high delays, high volumes, and extensive queuing. The methodology to determine LOS stratifies urban streeu into four classifications. The classifications are complex, and are related to functional and design categories. Table A-II describes the functional and design categories, while Table A-III relates these to the urban street classification.