Comparison of the Methodologies for Calculating Expressway Space Mean Speed Using Vehicular Trajectory Information from a Radar Detector

Abstract

This study was initiated to evaluate the performance of methodologies to estimate the space mean speed(SMS) using the time mean speed(TMS) which was collected from the vehicle detection system(VDS) in expressways. To this end, the methodologies presented in prior studies were firstly summarized. It is very hard to achieve exact SMSs and TMSs due to mechanical and communication errors in the field. Thus, a microscopic traffic simulation model was utilized to evaluated the performance. As a result, the harmonic mean and volume-distance weighted harmonic mean were close to the SMS in the case in which the TMSs of individual vehicles were used. However, when the 30-second-interval aggregated TMS were used, the volume-distance weighted harmonic mean was outstanding. In this study, a radar detector was installed in the Joongbu expressway to collect the SMS. The trajectory of individual vehicles collected from the detector were used to calculate the SMS, which was compared with the estimates using other methodologies selected in this study. As a result, the volume-distance weighted mean was turned out to be close to the SMS. However, as the congestion becomes severe. the deviation between the two speed becomes bigger.

A Novel Method about the Representation and Discrimination of Traffic State

“…Furthermore, time–mean–speed can be used as another embodiment of traffic density, which has been proved to be closely related to the state of traffic congestion in research [ 9 ]. In addition, the study [ 35 ] pointed out that road congestion becomes more serious, resulting in the deviation between the time–mean–speed and the space–mean–speed increases. According to the relationship between the two types of speed, we utilized the variance of the time–mean–speed observation value to express the deviation of the vehicle speed on the road, which can reflect the dispersion of the vehicle speed distribution.…”

“…Time–mean–speed ( ) refers to the arithmetic average of the speeds of all vehicles passing through a road section in a certain period. It is often used to evaluate the degree of congestion on the road and is one of the essential parameters that represent the traffic state in the statistical time interval [ 33 , 34 , 35 ]. The calculation equation is as follows:…”

Classification of Speed Change and Unstable Flow Segments Using Geohash-Encoded Vehicle Big Data

“…Various methodologies have been proposed for generating accurate vehicle speed data. Han [16] examined methodologies for calculating SMS on expressways, utilizing vehicle trajectory data from radar detectors. Ko [17] discussed the challenges of continuous micro-traffic analysis, contrasting prevalent image-based traffic analysis approaches with a microscopic traffic analysis framework using drone-acquired photographs.…”

Intersection Congestion Analysis Based on Cellular Activity Data

“…high maintenance, installation and operation costs to limit the practical applications of this method [4]. Therefore, space mean speed is usually adopted to analyze traffic state and status [5].…”