Level A | Free flow with low volumes and speeds controlled by speed limits, geometrics, etc. Very little interaction between vehicles. |
Level B | Stable flow with speeds beginning to be restricted by traffic conditions. |
Level C | Stable flow with moderate speed restriction caused by traffic. Most drivers feel restricted in their selection of speed and freedom to pass. |
Level D | Approaching unstable flow, with considerable restriction in speed. Operating speeds are tolerable, but comfort and convenience are low. |
Level E | Unstable flow with volume less than capacity and low operating speeds. Momentary stoppages of traffic. |
Level F | Forced flow with volume less than capacity and low operating speeds. Stoppages may be short or long duration with great delays. |
(a) Source data: Highway Capacity Manual - 1965, Special Report 87 of the Highway Research Board, and Handbook of Highway Engineering - 1982.
(Ord. 95-Z-01, passed 2-13-95)