Probe Data Sampling Guidelines for Characterizing Arterial Travel Time (original) (raw)

Frequency of probe reports and variance of travel time estimates

Journal of …, 1997

An important design issue relating to probe-based Advanced Traveler Information Systems (ATISs) and Advanced Traffic Management Systems is the sample size of probes (or the number of link traversals by probe vehicles) per unit time used in order to obtain reliable network information in terms of link travel time estimates. The variance of the mean of travel times obtained from n probes for the same link over a fixed time period may be shown to be of the form a+b/n where a and b are link-specific parameters. Using probe travel time data from a set of signalized arterials, it is shown that a is positive for well-traveled signalized links. This implies that the variance does not go to zero with increasing n. Consequences of this fact for probe-based systems are explored. While the results presented are for a specific set of links, we argue that because of the nature of the underlying travel time process, the broad conclusions would hold for most well-traveled links with signal control.

Parameters influencing probe vehicle based travel time estimation accuracy

2004

Floating Car Data (FCD) is becoming a more and more popular technique for travel time measurements in road networks. Nevertheless, FCD is a sampling technique which requires controlling the statistical properties of link travel times to obtain accurate estimations. Based on microsimulation outputs, this paper shows which parameters play a key role in the travel time estimation accuracy, particularly in the case of urban networks. Among them, aggregation period and link definition are the most critical ones. They must be properly chosen according to the equipped vehicles ratio.

Assessing Highway Travel Time Reliability using Probe Vehicle Data

Transportation Research Record, 2018

Probe vehicle data (also known as ''floating car data'') can be used to analyze travel time reliability of an existing road corridor in order to determine where, when, and how often traffic congestion occurs at particular road segments. The aim of the study is to find the best reliability performance measures for assessing congestion frequency and severity based on probe data. Pilot surveys conducted on A2 motorway in Poland confirm the usefulness and reasonable accuracy of probe data for measuring speed variation in both congested and free-flowing traffic. Historical probe vehicle data and traditional traffic counts from Polish S6 expressway were used to analyze travel time reliability on its 24 road sections. Travel time indexes and reliability ratings for the whole year 2016 were calculated to identify segments with lower reliability and higher expected delay. It is concluded that unlike the HCM-6 method, travel times obtained from probe data should be averaged in 1-hour intervals. Delay index is proposed as a new reliability indicator for road segments. Delay map diagrams are recommended for showing how the congestion spots move in space and with time of day. Probe vehicle data (PVD, also known as ''floating car data''), is a method of measuring traffic speed based on time-space data transmitted from GPS receivers and navigation devices in vehicles on the road. This method of obtaining information about traffic conditions in real time is used by navigation service providers and to aid traffic management. Long-term observations can be utilized to analyze highway travel time reliability; that is, to find how often traffic congestion occurs on a particular road segment. The paper presents intermediate results of research project MOP-DZ: ''Modern methods of calculating road capacity and assessment of traffic conditions on roads outside urban areas and express roads.'' The aim of the project is to update the Polish methods for evaluating traffic performance and estimating capacity for uninterrupted flow facilities. The project is jointly financed by the General Directorate for National Roads and Motorways and the Polish National Centre for Research and Development. It is being carried out by a consortium The project uses data from various sources, including traffic volume and speed data from permanent count stations , field surveys, and PVD. This last data category proved to be very useful for illustrating the emergence, spreading, and dissipation of congested regions as well as for assessing travel time reliability. Historical data from 16 weeks in 2015/16 for all national roads and motorways in Poland were used to examine travel time variability and to analyze how often unacceptable traffic conditions occur. The paper presents detailed analysis of a 36.5 km-long segment of S6 expressway, known as the Tricity Bypass Road. The study combined PVD with traffic counts from a permanent count station located at the middle section of the expressway.

Study on the Reliability of Travel Time Estimation by Probe Vehicle System

Asian transport studies, 2011

In order to provide reliable travel time information by probe vehicle system, a huge amount of travel time data should be collected. To minimize cost of data collection from probe vehicle with certain reliability level, the number of required probe vehicles and its optimal regional allocation should be examined. Therefore, this study proposes a new methodology to estimate the number of probe vehicles required to ensure the reliability of travel time estimation. It aims to verify the feasibility of reducing the number of probe vehicles from that required by the conventional methodology. Also, the feasibility of reducing probe vehicles by estimating travel time with existing traffic detectors is verified. The study concluded that the required number of probe vehicles estimated by the new methodology is less than that estimated by the conventional methodology, and that the use of probe vehicle systems leads to quick development of traffic information collection system.

Travel Time Estimation Using Cooperative Probes Vehicles

This document presents an application using cooperative probes data based on real-world field testing to estimate travel time by applying adaptive Monte Carlo method and adaptive estimation from probes. The purpose is conducting the two methods to check which one gives better results in the context of database enrichment. Moreover the process should be run on the historical database and also it has to do real time computations. The innovative part of this work can be summed up in three sections. The first one is related to digital mapping aspect, the second section is regarding the map-matching and GPS errors, and finally the adaptive estimation of travel time.

Travel time estimation for urban road networks using low frequency probe vehicle data

2012

ABSTRACT The paper presents a statistical model for urban road network travel time estimation using low frequency GPS probes as observations, where the vehicles typically cover multiple network links between reports. The network model separates trip travel times into link travel times and intersection delays and allows correlation between travel times on different network links based on a spatial moving average (SMA) structure.

Using Bus Probe Data for Analysis of Travel Time Variability

Journal of Intelligent Transportation Systems, 2009

The rapid progress of information technology (IT) may provide us new insights into understanding traffic phenomena, and could help mitigate traffic problems. One of the key applications of IT to traffic and transport analysis is the identification of the location of moving objects using the global positioning system (GPS) . It is expected that detailed traffic analysis could be carried out using these data. In this paper, we first summarise the various applications of probe data in transport analysis. GPS data is merely a sequence of locations, and further data transformation such as map matching, data reduction, processing, and reporting is needed to use them effectively. We then discuss the application of bus probe data to evaluating travel time variability and the level of service (LOS) of roads. A methodology for evaluating the road network from the viewpoint of travel time stability and reliability using bus probe data is proposed. Travel time distributions of arbitrary routes are estimated by statistically summing up directly observed multiple travel time distributions. Based on the development of methodologies to estimate travel time distributions of arbitrary routes covered by the bus probe survey, this study proposes an approach to evaluate the LOS of road networks based on the concept of travel time reliability.

Guaranteed Bounds on Highway Travel Times Using Probe and Fixed Data

88th TRB Annual …, 2009

This article investigates the problem of incorporating mobile probe data collected from GPS equipped cell phones into estimation algorithms for travel time. We use kinematic wave theory to create a modeling framework capable of incorporating trajectory data into the model. The problem of including loop detector data in this model is performed using a standard approach available in the literature. The problem of fusing this data with probe data is formulated using the Moskowitz function, which results from kinematic wave theory. Using this formulation, two linear programs are posed to compute upper and lower bounds travel time through the corresponding section of highway. The method thus provides a guaranteed range for the average travel time experienced by vehicles on the highway. The method is illustrated with data collected during the Mobile Century experiment on February 8th, 2008, using 100 Nokia N95 phones traveling onboard cars driving loops on I880 in California. A sampling and penetration rate study shows that the method provides accurate travel time estimates for penetration rates as low as 0:1% and spatial sampling strategies on the order of 0.2 miles. The performance of the method is illustrated with several case studies, in which measurements gathered by a few vehicles are sufficient to significantly improve results obtained from sparse loop detectors.