RITA | ITS | Benefits: Adaptive signal control systems reduce intersection delay up to 18% in Los Angeles

Adaptive signal control systems reduce intersection delay up to 18% in Los Angeles

Nearly 2,500 of the over 4,000 traffic signals in Los Angeles use adaptive signal control to adjust traffic signal timing based on current traffic demand. Studies at seven of these intersections found delay reduced by an average of 10%, with reductions ranging from 3.1% to 17.7%. Performance of adaptive signal control systems at each of the seven intersections was measured using data collected by the Los Angeles Advanced Traffic Control and Surveillance System (ATSAC). The amount of time that the light would remain green was based on the volume of traffic detected at that signal’s previous cycle. After the system was deployed, overall intersection delay decreased by an average of 10%, and level-of-service (LOS) improved. Performance at 4 of the intersections improved, while no change was measured at the remaining 3. The percentage of cycles with improved LOS at these four intersections ranged from 27 to 55%. The only decreases in LOS for any of the cycles at the four intersections with changes in LOS were 5% of the cycles at two of the locations. The benefits of adaptive signal control were greatest for the two-phase intersections having exclusive turning lanes, and/or unbalanced critical volumes. Benefits were considerably lower at intersections with multiple phases (e.g. advanced greens for left turns) due to the minimum time required for each phase, leaving little flexibility for adjusting the green time given to each traffic movement.

See the related ITS Benefits Database entry for more information.

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