Trajectory-based characterization of spatial speed adaptation under speed feedback configurations in a freeway work zone

Speeding in Work Zones (WZs) remains a major safety concern. Although speed feedback devices offer a non-enforcement alternative, conventional point-speed evaluations provide limited insight into spatial speed adaptation. This study uses high-resolution vehicle trajectories to examine three feedback systems: Dynamic Speed Feedback Sign (DSFS), Speed Wizard (SW), and SW combined with Portable Changeable Message Sign (PCMS). The framework integrates Pruned Exact Linear Time change-point detection, Spatial Lag Model, and Local Discontinuity Analysis to characterize spatial transitions, account for spatial dependence, and assess localized speed changes. All feedback condition-days were associated with lower speeds than the no-feedback condition-day. Estimated total associations were −2.81 mph for DSFS, −3.84 mph for SW, and −2.93 mph for SW+PCMS. A prominent speed transition was repeatedly identified approximately 400–500 ft downstream of the feedback sign, with localized patterns varying across conditions. The findings demonstrate the value of trajectory-based spatial analysis for characterizing speed adaptation in WZs.