ACS-Lite Split Tuning Algorithm

Collect data Correlate data to signal phasing Perform analysis Implement phase split adjustments

Occupancy Data is collected from stop bar detectors. Inductive Loops, Video and Radar detectors have worked effectively with ACS-Lite.

Ø3 Ø8 Ø7 Ø4 Ø8 Ø4 Ø7 Ø3 Ø8 Ø5 Ø2 Ø7Ø4 Ø1 Ø6 Ø5 Ø2 Ø5 Ø2 Occupancy data is correlated to phase intervals by the intersection controller. This data is sent to ACS-Lite allowing phase utilization information to be developed for each cycle.

ACS-Lite averages the phase utilization data for several cycles to determine the degree of saturation for each phase. Averaging Ø3 Cycle 1 Ø3 Cycle 2 Ø3 Cycle 3 Ø3 Cycle 4 Ø3 Phase Utilization

ACS-Lite balances the degree of saturation for all phases by adjusting splits. The result is more efficient use of available green time across all phases. Ø3Ø8 Ø5 Ø2 Ø7Ø4 Ø1 Ø6

Split Adjustment Example The following slides present an example of the ACS-Lite split adjustment algorithm. A software in the loop simulation was developed using CORSIM with an NTCIP runtime extension to interface with the ACS-Lite software. The simulation was conducted on SR-26 in Lafayette, IN. The simulation runs for one hour beginning at 7:00am, snapshots are provided at key times throughout the hour to demonstrate the outcome of split tuning.

Ø3Ø8 Ø5 Ø2 Ø7Ø4 Ø1 Ø6 ACS-Lite has collected data for 5 cycles. The N/B Left Turn (Phase 3) is reporting a 100% degree of saturation. The intersection is running a 70sec cycle with a 10 second split for Phase 3. ACS-Lite is ready to implement a split adjustment.

Ø3Ø8 Ø5 Ø2 Ø7Ø4 Ø1 Ø6 The first split adjustment was implemented just after 7:06am increasing the phase 3 split from 10 to 13 seconds. After the adjustment data is collected for 5 cycles. The N/B Left Turn (Phase 3) continues to report a 100% degree of saturation. ACS-Lite is ready to implement a second split adjustment.

Ø3Ø8 Ø5 Ø2 Ø7Ø4 Ø1 Ø6 The second split adjustment was implemented just after 7:14am increasing the phase 3 split from 13 to 15 seconds. Phase utilization data is collected for 5 cycles. The N/B Left Turn (Phase 3) continues to report a 100% degree of saturation; notice the queue has been reduced. ACS-Lite is ready to implement a third split adjustment.

Ø3Ø8 Ø5 Ø2 Ø7Ø4 Ø1 Ø6 The third split adjustment was implemented just after 7:24am increasing the phase 3 split from 15 to 17 seconds. After the adjustment data is collected for 5 cycles. The N/B Left Turn (Phase 3) continues to report a 100% degree of saturation; notice the queue has been eliminated. ACS-Lite recognizes that this is the optimal split for the current phase 3 demand.

Ø3Ø8 Ø5 Ø2 Ø7Ø4 Ø1 Ø6 After collecting data for 5 additional cycles ACS-Lite retains the N/B Left Turn (Phase 3) split at 17 seconds. The degree of saturation has been balanced across all the phases. As conditions change ACS-Lite will make the appropriate split adjustments.

Ø3Ø8 Ø5 Ø2 Ø7Ø4 Ø1 Ø6 After collecting additional data, ACS-Lite retains the N/B Left Turn (Phase 3) split at 17 seconds. The intersection is operating optimally. Additional split changes will be made as necessary to meet the demand needs of the intersection.

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