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The following brief explanation of the level-of-service concept will aid understanding of the basis for the comparisons made in the analysts. "Level-of-service" is a term which denotes any o(a number of combinations of traffic operating conditions that may occur on a given roadway when it is suhiect to various traffic volumes. Factors such as speed, travel time, traffic interruption, freedom to maneuver, safety, driving comfort and convenience affect the determination of level-of•service. Analytically, it is related to a ratio of the traffic volume to the theoretical traffic capacity of the roadway or intersection (V/C ratio). There are six levels-of-service, A through F, which describe driving conditions from best to worst, respectively. They are described as follows: • Level-of-service A represents uncongested, free-flow conditions. On a two- lane road, passing demand is well below passing capacity. Drivers would be delayed no mitre than l0 percent u!'the tune by slow moving vehicles. For multi-lane highw;iys, the ability to maneuver within the traffic stream is high. Minor tr_ffic how r{~~ruptions at this level are easily absorbed without causing significant delays or queuing. • Level-ot•service B is indicative of a stable flow where the presence of other vehicles begins to be noticeable. As passing demand approaches capacity on two-lane roadways, placooning is common. At this level, minor traffic disruptions are still easily absorbed, but local deterioration in LAS will be more obvious. ' • LRVel-of-service C represents conditions at which noticeable delays occur and the freedom to maneuver between lanes becomes restricted. Slowing of traffic is particularly noticeable when vehicles turn Iclt and passing capacity iti reduced • level-of-service t) represents congestion and the limits of stable traffic flow. Traffic congestion severely restricts speeds anti the ability to maneuver Unly the most minor of traffic disruptions can occur without extensive yueueti forming. On two-lane roads, passing demand iti high while passing capacity approaches zero. • Level-of-seMce E represents unstable traffic flow operations at or near capacity. Any disruption, no matter how minor, causes queues and deterioration of LAS. Passink becomes virtually impossible on two-lane roadways. • Level-of-service F represents heavily congested flow with the traffic demand exceeding capacity Operation within queues are very unstable, with traffic experiencing short spurts of movement followed by stoppages. ^ LC... .1.-......,. vP.,.,,, rl,. r. n.+ Ii1P nPr•i nit 197H Ifl 19U2