Feeding SPaT Countdown Timers into Speed-Advisory and Motion-Planning Software

The software pipeline that converts a SPaT minEndTime/maxEndTime countdown into a Green Light Optimal Speed Advisory recommendation and an Intersection Movement Assist risk score inside the vehicle's ADAS stack.

Treating SPaT Timing as a Probabilistic Signal, Not a Fixed Clock

Actuated intersections in the field frequently extend green phases for detected traffic, meaning the maxEndTime field can shift upward between consecutive SPaT broadcasts. The ADAS fusion module tracks the historical variance of each SignalGroupID's countdown drift and widens its confidence interval accordingly rather than trusting a single frame at face value.

Coupling GLOSA Output with the Longitudinal Motion Planner

A GLOSA speed band is only useful if the vehicle's longitudinal motion planner can act on it. The V2I application publishes a target speed range and an intersection-clearance deadline over the internal ADAS bus; the planner then blends this advisory input with forward radar and lead-vehicle spacing before adjusting throttle or regenerative braking.

Kalman-style smoothing of successive SPaT countdown updates to suppress jitter from actuated signal extensions.
GLOSA speed-band computation that respects posted speed limits, vehicle kinematics, and passenger comfort constraints.
Dilemma-zone risk scoring that flags approach speeds where neither safe stopping nor clearing the intersection is guaranteed.
Graceful degradation to camera-only traffic-light recognition when SPaT confidence drops below a calibrated threshold.

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