Traffic Flow Characteristics of an Urban Arterial Based on Different Traffic Flow Models

Four different single-regime traffic flow models (Greenshields, Northwestern, Underwood and Van Aerde) were used to develop fundamental diagram (FD) relations for an urban corridor segment in Ankara, Turkey. Fundamental diagrams were obtained using 1-min average speed and flow data digitized from 2-day video recording of the arterial segment. The model fits enabled the estimation of main traffic flow characteristics including free-flow speed (uf), jam density (kj), and flow, density and speed values at capacity (qcap, kcap, ucap). Performance of model fits was measured by R2 values, which were greater than 0.86 for all models. For lane-based fits, Van Aerde and Underwood performed better than other two models and showed significant variations among lanes in terms of uf, kj and qcap. Outermost lanes were expected to have higher uf and qcap values than inner lanes, reaching levels of 110 km/h and 2000 veh/h/ln, which are closer to intercity highway levels. Flow estimated by selected models had Mean Absolute Percentage Error (MAPE) mostly around 15% and Root Mean Square Error (RMSE) of 250 veh/h/ln; but Van Aerde model performed very well with MAPE and RMSE values less than 13% and 200 veh/h/ln, respectively. Furthermore, verification by site observation under early morning low volume and incident congestion situation supported the traffic flow estimates by Van Aerde model as the most flexible flow model successfully representing the limiting values under both free flow and very congested regimes.
Citation Formats
O. Altıntaşı, H. Tüydeş Yaman, and K. Tuncay, “Traffic Flow Characteristics of an Urban Arterial Based on Different Traffic Flow Models,” presented at the 13th International Congress on Advances in Civil Engineering, (12 - 14 Eylül 2018), İzmir, Türkiye, 2018, Accessed: 00, 2021. [Online]. Available: