In|Sync How it Works

How In|Sync’s Real-Time Adaptive Traffic Control Works

Converting Analog Operations to Digital Operations

In|Sync’s digital state architecture allows it to react in real time to changing traffic conditions. In In|Sync’s advanced traffic management system, a “state” is a phase pair — any two phases that can be served concurrently. The system chooses the state that best serves traffic conditions based on second-by-second analysis. With the digital ability to move to any desired state, In|Sync overcomes the limitations of traditional ring-based systems — it is not constrained to a pre-programmed, cyclic order of operations. Using both real-time data and parameters set by the traffic engineer, In|Sync can dynamically choose states, alter sequences and adjust the amount of green time to best serve actual traffic demand and be a fully adaptive signal control system.

This chart shows the eight north-south sequences used in conjunction with eight east-west (not shown) sequences. Your agency’s preferences shape the options available. In|Sync simplifies a wide range of signalization possibilities to digital choices so it can quickly adapt to actual demand.

Local Optimization

In|Sync’s local optimizer focuses on minimizing delay of individual movements at each intersection by constantly measuring the number of vehicles queued in each lane and calculating their time in the queue. In|Sync’s adaptive traffic management system focuses on how to best reduce those numbers using an algorithm that evaluates the aggregated demand and wait time for each phase and serves states accordingly.


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How In|Sync Adapts to Local Traffic Demand

In|Sync’s local optimizer employs three different adaptive strategies to maximize local responsiveness and flexibility with its adaptive traffic control.

Dynamic Phasing

As a digital state machine, In|Sync overcomes the limitations of fixed timing plans. In|Sync isn’t locked into any pre-determined order and can move to serve phases that best serve real-time traffic demand.

Dynamic Sequencing

In|Sync dynamically chooses from a library of user-defined sequences to serve current traffic demand. This dynamic phasing allows the adaptive traffic management system of In|Sync to change the order of phases to meet the real-time demands of an intersection. The ability to define states and sequences per configuration ensures that states can be included or excluded according to local regulations or traffic agency needs.

Dynamic Green Time Allocation

In|Sync adjusts green time according to real-time demand and intersection geometry. The number of vehicles present helps determine how much or how little green time to allocate to a phase, and an occupancy-based gap-out analysis eliminates wasted green time.

Global Optimization

In|Sync’s global optimizer ensures vehicles experience as few stops as possible along a corridor by guaranteeing green time for mainline movements at each intersection. This scheduled green time creates “green tunnels” that move platoons of vehicles through the corridor, improving travel time, reducing fuel use and emissions, and making commutes safer.

If any In|Sync intersection sees a significant change in demand, the adaptive traffic management system can make a global decision to add more or less time between scheduled movements to best serve all phases. Rhythm Engineering works with each agency to design a tunnel structure which achieves true bi-directional coordination and progression for mainline movements.

Adjusting to Corridors’ Changing Traffic Demand

Tunnel Duration

Based on actual demand, In|Sync can modify the adaptive traffic control’s green time allocated to a coordinated movement. If the traffic volume approaching a specific intersection decreases and reaches a minimum threshold, In|Sync can truncate the duration of the green tunnel at that intersection. Additionally, the global optimizer can extend the duration of a green tunnel if traffic volume spikes.


The period is a defined interval from the start of a green tunnel to the start of the same green tunnel later in time. Using dynamic adjustments, In|Sync can modify the frequency of green tunnels within a certain range to adjust to fluctuations in demand on secondary movements.

Collaboration Between Global and Local Optimizers

During unscheduled, uncoordinated periods of time, In|Sync switches to the local optimizer to dynamically serve intersection traffic based on real-time volume and delay analysis. All phases with demand are guaranteed service from the adaptive signal control In|Sync before the next platoon of vehicles arrives at the intersection, ensuring no phase is skipped and all minimum parameters are considered in In|Sync’s algorithm.

The In|Sync Interface

In|Sync’s interface is an interactive, easy-to-use command center for monitoring and problem solving with flexibility — all from the comfort of your desk. In|Sync Web UI can be accessed from your computer, tablet or mobile device to view any of the In|Sync cameras in your system — all on one page. If issues arise, the interface allows you to troubleshoot intersections, reboot cameras or turn on emergency mode, without ever having to travel to the cabinet.

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