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109 <br />The relationship of travel demand compared to the roadway capacity determines the <br />level of service (LOS) of a roadway. Six levels of service identify the range of possible <br />conditions. Designations range from LOS A, which represents the best operating <br />conditions, to LOS F, which represents the worst operating conditions. <br />Design requirements for roadways vary according <br />service. LOS D indicates "practical capacity" of a r <br />public begins to express dissatisfaction. Recon <br />design of the transportation plan were based up+ <br />existing facilities and a LOS C on new facilities. Tt <br />below and illustrated in Figure 11. <br />to the desired capacity and level of <br />iadway, or the capacity at which the <br />mended improvements and overall <br />n achieving a minimum LOS D on <br />six levels of service are described <br />LOS A: Describes primarily free flow conditions <br />level of physical and psychological comfort. <br />breakdown are easily absorbed. Even at the ma <br />between vehicles is about 528 ft, or 26 car length <br />LOS B: Represen <br />the traffic stream <br />vehicles is about <br />LOS C: Provides 1 <br />increases will cau <br />noticeably restrict( <br />service will be gr <br />blockaqe. Minimu <br />)nly slightly re <br />ft, or 18 car len <br />• LOS D: Borders on un =. <br />quickly with increasing <br />deterioration in service. <br />experiences drastically r <br />create substantial queuii <br />lengths. <br />ow conditions. <br />ie motorist experiences a high <br />effects of minor incidents of <br />m density, the average spacing <br />ability to maneuver within <br />verage spacing between <br />ble operations, but flows approach the range in which small <br />astantial deterioration in service. Freedom to maneuver is <br />inor incidents may still be absorbed, but the local decline in <br />Queues may be expected to form behind any significant <br />rage spacing is in the range of 220 ft, or 11 car lengths. <br />e flow. Density begins to deteriorate somewhat more <br />w. Small increases in flow can cause substantial <br />eedom to maneuver is severely limited, and the driver <br />ced comfort levels. Minor incidents can be expected to <br />At the limit, vehicles are spaced at about 165 ft, or 9 car <br />LOS E: Describes operation at capacity. Operations at this level are extremely <br />unstable, because there are virtually no usable gaps in the traffic stream. Any <br />disruption to the traffic stream, such as a vehicle entering from a ramp, or changing <br />lanes, requires the following vehicles to give way to admit the vehicle. This can <br />establish a disruption wave that propagates through the upstream traffic flow. At <br />capacity, the traffic stream has no ability to dissipate any disruption. Any incident <br />can be expected to produce a serious breakdown with extensive queuing. Vehicles <br />are spaced at approximately 6 car lengths, leaving little room to maneuver. <br />E -1 <br />