WSDOT - Level of Service Standard for State Routes

WSDOT sets level of service (LOS) standards for state highways and ferry routes of statewide significance (HSS) based on RCW 47.06.140(2). Regional transportation planning organizations (RTPOs) and WSDOT jointly develop and RTPOs establish LOS standards for regionally significant state highways and ferry routes (non-HSS) based on RCW 47.80.030(1)(c). LOS is based on peak-hour except where noted. Level of Service Standard is used by planners to determine the effectiveness of a roadway network. LOS assigns a rank (A - F) to road sections based on traffic flow and corresponding safe driving conditions. The Highway Capacity Manual and AASHTO Geometric Design of Highways and Streets ("Green Book") list the following levels of service: A = Free flow, B = Reasonably free flow, C = Stable flow, D = Approaching unstable flow, E = Unstable flow, E Mitigated = Congestion should be mitigated (such as transit) when p.m. peak hour LOS falls below LOS "E", F = Forced or breakdown flow This dataset is used as a general reference layer for geographic information systems at the Washington State Department of Transportation, and is updated as needed.华盛顿州交通部（Washington State Department of Transportation, WSDOT）依据华盛顿州修订法典（Revised Code of Washington, RCW）第47.06.140条第2款，为具有全州重要性的州级公路及渡轮航线（Highway System Statewide, HSS）制定服务水平（Level of Service, LOS）标准。区域交通规划组织（Regional Transportation Planning Organizations, RTPOs）与WSDOT联合开展相关制定工作，并由RTPOs依据RCW第47.80.030条第1款第c项，为区域重要性州级公路及渡轮航线（非HSS）确立服务水平标准。除另有说明外，服务水平（LOS）均以高峰小时为基准。服务水平标准可供规划人员评估道路网络的运行效能：其根据交通流量及对应安全驾驶条件，为道路路段赋予A至F的等级。《道路通行能力手册》（Highway Capacity Manual）与美国公路与运输员工协会（American Association of State Highway and Transportation Officials, AASHTO）《公路及街道几何设计规范》（俗称"绿皮书"）列明了如下服务水平等级：A=自由流，B=合理自由流，C=稳定流，D=接近不稳定流，E=不稳定流，E（缓减型）=当晚高峰时段服务水平低于"E"级时，需采取公共交通等措施缓解拥堵，F=强制流或流量崩溃流。本数据集作为华盛顿州交通部地理信息系统的通用参考图层，可根据实际需求更新。