Network Efficiency and Velocity Decay in Asymmetric Urban Corridors: An Empirical Baseline for AI-Integrated Traffic Control in Buea, Cameroon

Urban road networks in sub-Saharan Africa diverge from traditional sensor-rich, lane-disciplined environments. This paper established an empirical baseline assessment of network efficiency and velocity decay along the 8.0km Mile 17 to Governor's Roundabout corridor (8.0 km) in Buea, Cameroon. Characterized by radial geometry, a steep 25 m/km inbound gradient, unsignalized intersections, and a high mix informal transport (taxis comprising 59.5% and 65.27 of traffic for inbound and outbound flow, respectively). Fifteen-minute Passenger Car Unit (PCU) volume counts were recorded at three measurement points evaluated across three peak windows (morning, afternoon, and evening) over three consecutive weekday observation days. Volume-to-capacity ratios (v/c), peak-hour factors (PHF), equivalent hourly flow rates, space-mean speeds, and Mean Travel Time Indices (MTTI) were calculated for both inbound and outbound flow directions. Results reveal near-saturation and over-saturation at the Bonduma mid-corridor point during morning and afternoon peaks (v/c: 0.98 to 1.06). The highest operational stress occurred during the afternoon outbound window, where over-capacity conditions emerged simultaneously at Mile 17 and Bonduma. MTTI values ranged from 1.36 to 2.04, indicating that congestion is primarily driven by informal transport dynamics rather than absolute vehicle volume. Finally, the paper introduces the Directional Flow Asymmetry Index (DFAI) and Corridor Velocity Decay Rate (CVDR) to successfully quantify critical directional imbalances that traditional aggregate v/c analysis fails to resolve.