Free-Flow Speed Profile Prediction for Tangent Segments on Urban Roads

Abstract

The free-flow speed profile is one of the essential elements in the design and operation of the roads. The speed profile is employed to improve road design, traffic emissions models, fuel consumptions models, evaluate the consistency, among others. Speed profiles are built with speed, acceleration, and deceleration models. Therefore, understanding how different factors affect speed, acceleration, and deceleration is a critical research question. Many studies have focused on rural roads and only a few on urban roads. In urban environments, studies did not yet reach conclusive results. This research attempted to address these limitations by developing speed, acceleration, and deceleration models in urban tangents under free-flow conditions in the city of Loja, Ecuador. Three different tangents were selected: before stop-controlled intersections, before signal-controlled intersections, and before roundabout intersections. Speeds of light vehicles, equipped with GPS, were collected in 13 tangents with 45 drivers. Geometric and operation characteristics were also collected: geometric elements of the street, street environment, driver, and vehicle-related. Forty-five speed, acceleration, and deceleration regression models were calibrated and validated. This research expands the knowledge of the most influential variables on speed in various urban settings, offering useful information for city planners and designers.