Analysis of Traffic Flow Lags Between Motorway Traffic Counters

Understanding how traffic flow dynamics evolve across the urban motorway network is critical for designing effective traffic management strategies. This study presents an empirical analysis of spatio-temporal traffic flow patterns along the east-to-west motorway corridor encircling the city of Zagreb. Using a dataset obtained from the Croatian National Access Point and the company Ericsson Nikola Tesla, we apply a combination of the Pearson Correlation Coefficient, Cross-Correlation Analysis, and Quan-tile–Quantile Analysis (QQA) to investigate flow homogeneity, directional lag effects, and flow distribution differences across motorway sections. Our findings reveal that most sections exhibit strong spatial coherence, with high cross-correlation and minimal lag under normal traffic conditions. However, directional lag patterns are observed across segments, suggesting measurable propagation of congestion waves during the rush hours. The QQA also highlights localized differences in extreme flow behaviors, indicating traffic discontinuities that are correlated with inherent motorway geometric features (like on- and of-ramps that connect it with the urban traffic network) and demand variations. Thus, the results provide a detailed information about the spatio-temporal traffic flow coupling and propagation, allowing for the detection of critical traffic features and patterns, as well as the origins of their creation, which can be considered candidates for the deployment of dynamic proactive traffic management services.