Term
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Definition
| providing less mobility and a moderate amount of land access, distributing travel to smaller areas, while interconnecting the major roads |
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Term
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Definition
| providing direct access to the adjacent land and access to the higher classified roads |
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Term
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Definition
| free-flow operations. Traffic flows at or above the posted speed limit and all motorists have complete mobility between lanes. The average spacing between vehicles is about 550 ft(167m) or 27 car lengths. Motorist have a high level of physical and psychological comfort. |
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Term
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Definition
| reasonable free-flow operations. Free-flow (LOS A) speeds are maintained, maneuverability within the traffic stream is slightly restricted. The lowest average vehicle spacing is about 330 ft(100m) or 16 car lengths. Motorist still have a high level of physical and psychological comfort. |
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Term
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Definition
| Stable flow or at or near free-flow operations. Ability to maneuver through lanes is noticeably restricted and lane changes require more driver awareness. Minimum vehicle spacing is about 220 ft(67m) or 11 car lengths. |
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Term
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Definition
| Approaching unstable flow.Freedom to maneuver within the traffic stream is much more limited and driver comfort levels decrease. Vehicles are spaced about 160 ft(50m) or 8 car lengths. Minor incidents are expected to create delays. |
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Term
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Definition
| Unstable flow or operations at capacity. Flow becomes irregular and speed varies rapidly because there are virtually no usable gaps to maneuver in the traffic stream and speeds rarely reach the posted limit. Vehicle spacing is about 6 car lengths, however speeds are still at or above 50 mi/h(80 km/h). Any disruption to traffic flow, such as merging ramp traffic or lane changes, will create a shock wave affecting traffic upstream. |
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Term
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Definition
| Forced or breakdown in vehicular flow. Flow is forced; every vehicle moves in lockstep with the vehicle in front of it, with frequent slowing required. Technically, a road in a constant traffic jam would be at LOS F. This is because LOS does not describe an instant state, but rather an average or typical service. |
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