The “meta SBA” project, carried out from 2018 to 2024 under the German Federal Ministry of Transport’s funding, examined the effectiveness of collective traffic‑management devices, specifically segment‑based controls (SBAs) and ramp‑metering systems (ZRAs). The consortium, led by the research group commeaT.E.C. and supported by the University of Bielefeld (UniBw), produced a comprehensive report that synthesises existing studies, develops new evaluation methods, and proposes future research directions.

The technical core of the report is a meta‑analysis of safety, traffic‑flow, and environmental impacts of SBAs and ZRAs. For safety, the analysis aggregated accident‑rate reductions reported in the literature, confirming that well‑implemented SBAs can lower crash frequencies by up to 15 % in high‑volume corridors. Flow‑related findings show that SBAs stabilize traffic streams, reducing average travel‑time variability by roughly 20 % and shortening congestion lengths by 10–15 % in typical motorway sections. The environmental assessment, based on the HBEFA emissions handbook, indicates that the combined effect of speed‑regulation and lane‑closure measures can cut CO₂ emissions by 5–8 % per vehicle kilometre, largely due to smoother traffic and lower idling times.

Methodologically, the report distinguishes between ex‑ante and ex‑post evaluation frameworks. Ex‑ante models use simulation and scenario analysis to predict expected benefits before construction, while ex‑post studies rely on empirical data collected after deployment. The authors recommend a “before‑after” comparison with matched control sections, supplemented by “ideal” no‑control periods where traffic conditions are manually replicated. They also propose a new ex‑post calculation for traffic‑flow benefits that incorporates local traffic‑volume data and accounts for stochastic variations, thereby improving the reliability of benefit estimates.

The report further identifies suitable application zones for SBAs and ZRAs. SBAs are most effective on stretches with recurrent congestion, weather‑related slowdowns, or high accident rates, whereas ZRAs excel at merging points where upstream traffic pulses can be smoothed. The authors suggest that future studies should integrate high‑resolution sensor data and machine‑learning techniques to refine predictive models and to capture context‑specific effects that current generic models overlook.

In terms of collaboration, commeaT.E.C. coordinated the project, overseeing data collection, analysis, and dissemination. UniBw contributed methodological expertise, particularly in statistical modelling and emissions calculations. The project’s deliverables include a detailed handbook for emissions factors (HBEFA), a set of guidelines for SBA and ZRA evaluation, and a series of case studies illustrating the application of the proposed methods. The final report, dated 26 January 2024, consolidates these findings and outlines a roadmap for updating existing VBA assessment procedures to reflect the latest scientific evidence.

Overall, the meta SBA project delivers a robust evidence base that confirms the safety, flow, and environmental benefits of SBAs and ZRAs, while providing practical tools and recommendations for policymakers and engineers to optimise the deployment and evaluation of collective traffic‑management devices on Germany’s high‑capacity road network.