Empirical Analysis of Vehicle Time Headways and Speeds on Rural Two-Lane, Two-Way Roads

Abstract

Accurate knowledge of vehicle time headway (TH) and speed distributions is essential in many traffic engineering applications, such as capacity and level-of-service analysis, and in several contexts (operations at road segments, priority junctions, roundabouts, merging maneuvers). Other fields of interest are represented by vehicle generation in traffic microsimulation models and driving simulation applications. This paper presents results from an experimental analysis of vehicle TH and speed distributions on two-lane, two-way roads. The focus is on rural roads in Northern Italy, which are characterized by various levels of traffic and where data were collected by radar sensors. A trendless analysis of observed THs was carried out. Analysis then focused on estimating a well-known TH model, gamma-generalized queuing. Statistical analysis of the available data allowed testing of a set of speed distribution models, highlighting their goodness of fit with reference to empirical distributions. Completing the analysis, bivariate distributions were estimated to represent headway and speed distributions. The traffic parameters considered to affect TH distributions were flow rate and flow composition (percentage of heavy vehicles). Exogenous conditions, such as weather and road geometric futures, were common to all analyzed time periods and cross sections. The final goal of the analysis was to create a picture of the relationship between traffic conditions and speed and headway distributions for a typical road

Two Vehicular Headways Time Dichotomic Models

“…AA., 2001; for a calibration technique see Luttinen, 1996). Nowadays, the vehicular time headways is back again of great interest in the field of road engineering applications (Ha et al, 2010Rossi, 2012). The present work is thus contributing to this renewed interest about vehicular headways.…”

“…Griffiths & Hunt, 1991;Sullivan & Troutbeck, 1994;Luttinen, 2003;Rossi, 2012): the distribution of time headways contributes to the determination, for instance, of the characteristics of overtaking manoeuvres, of merging and intersection, whereas the capacity of many elements of the infrastructural system is generally ruled by minimum vehicular time headway and by the distribution of time headways under saturation conditions. These circumstances have always motivated the theoretical knowledge of the vehicular time headways and in particular, the research of realistic models in conditions of uncertainty to use in simulation procedures, in traffic control and in functional road planning.…”

Fitting Time Headway–Vehicle Speed Bivariate Distributions

“…Field validity was the main objective because a good approximation of empirical TH and VS distributions was desired. A good trade-off among these criteria was represented by the • Gamma-GQM as TH model (11,14,16,19) and • Skew-T distribution as VS model ( 12), unimodal or bimodal as required (18).…”

“…The Farlie-Gumbel-Morgensten (FGM) approach to building bivariate distributions was then applied to a set of data to represent concurrently TH-VS distributions at cross sections (19). The traffic parameters considered to affect TH-VS distributions were flow rate [vehicles per hour per lane (vphpl)] and flow composition [percentage of heavy vehicles (HVP)] along the analyzed direction-lane.…”

Harmonization and synchronization model of interrupted traffic flows on motorways

“…The paper includes solution to theoretical aspect of harmonization (adjustment of one traffic flow in case that parts of it are interrupted) and synchronization (adjustment of two opposite traffic flows in case that parts of them are interrupted on two carriageways) of traffic flows during temporary traffic regulation with temporary signalisation on motorway in place (Akçelik et al 1997). Newer research on this topic is addressed in current literature (Tiaprasert et al 2015;Rossi et al 2014;Lee et al 2015;Clempner, Poznyak 2015).…”