Arterial Travel Time Research Articles

Integrated ANN-Bayes-based travel time prediction modeling for signalized corridors with probe data acquisition paradigm

Travel time is a major information in support of Transportation System Management and Operations (TSMO). Accurate travel time information extracted from probe data sources, which have been evolved in recently years, has led to the considerable research into travel time prediction modeling on freeways. However, little research has been reported on dealing with predicting signalized arterial travel time. It is mainly because of the natures of interrupted traffic flows along a signalized corridor or dynamic urban network, wherein varying signal timing schemes, crossing traffic, and dynamic route choices make arterial travel time estimations much more challenging than freeways. This paper presents an innovative methodological framework that can be used to integrate the exponential smoothing technique, Artificial Neural Network (ANN) techniques and Bayes algorithms for predicting travel time along a signalized corridor. The data source obtained along the US-27 corridor in the State of Ohio, was used to test two types of the developed models, i.e., hourly instantaneous travel time prediction model and realized (or experienced) route travel time prediction model. The study results indicate that the developed models can effectively capture the travel time patterns by combining an exponential smoothing base profile and an ANN-Bayes-trained dynamic profile. In this way, more sensitive changes can be identified to a variation aroused by non-recurring congestion. The testing results with real-world travel time datasets indicates a good performance of the predicted travel time models. The most errors range from −0.608 to 0.485, which are much lower than the threshold standard deviation if 2.24 and close to 6% of mean travel time value of 9.08 min. Overall, the study results suggest that the proposed methods are capable of capturing traffic patterns even when an incident occurs by comparing with conventional methods.

Link Travel Time Estimation for Arterial Networks Based on Sparse GPS Data and Considering Progressive Correlations

Understanding complicated city traffic patterns has been recognized as a critical goal by twenty-first-century urban planners and traffic management systems, resulting in a significant rise in the quantity and variety of traffic data gathered. For example, in a growing number of large cities, taxi firms have begun collecting metadata for each vehicle trip, such as origin, destination, and travel duration. Taxi data offer information on traffic patterns, allowing the study of urban flow – what will traffic look like between two sites on a particular day and time in the future? This paper proposes a method based on sparse GPS probe data, that focuses on allocating travel time data to the different links traveled between GPS observations. This model incorporates the progressive spatial correlations between the links in a network. The main goal of this work is to show how we can consider progressive spatial correlations and improve our results more realistically with a simple adjustment in the previously known parametric methods. For estimating arterial travel time, the methodology is applied to a case study for the partial network of New York City-based on the data collected from the taxicabs in New York City, providing the locations of origins, destinations, and travel times. The model estimates quarter-hourly averages of urban link travel times using OD trip data. This study proposes a more accurate approach for estimating link travel times, that fully utilizes the partial information received from taxi data in cities.

TRAVEL TIME ANALYSIS OF SELECTED URBAN STREETS IN BAGHDAD CITY

Estimating travel time and measuring speed are critical for increasing the efficiency and safety of traffic road networks. This study presents an investigation of arterial travel time estimation for vital routes in Baghdad city. These estimations including speeds, stops, and delays were computed via GPS device and compared to those currently used to quantify congestion and travel time reliability. The study involved a 45-day survey of private vehicles in Baghdad utilizing a Global Positioning System (GPS) probe to collect data on traffic performance metrics for analysis in a GIS context. It was found that the proposed travel time performance measures show definite differences in estimates of peak-hour travel time as compared with weekend travel time. Route (1) from Bayaa intersection - Bab Al-Mutham intersection (through highway) produced a travel time of 165 minutes and 136 minutes for Bayaa intersection - Bab Al-Mutham intersection (through downtown). The travel speed of routes 1 and 2 are observed near 25 kmph which is below the local speed limit of 70 kmph. The maximum travel time of routes 1 and 2 are 71 minutes and 37 minutes, respectively. While delay time was observed 45 and 20 minutes due to traffic congestion on route 1 and 2, respectively. The majority of vehicles are capable of traveling at normal speeds, with relatively few exceeding them.

Validating and Calibrating the Highway Capacity Manual Arterial Travel Time Reliability Methodology

The 6th edition of the Highway Capacity Manual (HCM6) introduced a methodology for estimating and forecasting arterial travel time (TT) distributions (TTD) and their associated travel time reliability (TTR) metrics. Recently, it was shown that the HCM6 severely underestimated both the TTD and the TTR metrics for a test network in Lincoln, NE, U.S. Subsequently, it was shown that the underestimation issue could be eliminated through a proposed calibration methodology. Because this validation and calibration work was done on a single, relatively short section of arterial roadway there is an open research question on whether this finding applies to longer and more congested arterial roadways. The goal of this paper is to validate and calibrate the HCM6 TTR methodology on five arterial roadway testbeds that are longer and more congested than the original testbed. Empirical data from the National Performance Management Research Data Set (NPMRDS) which is managed by INRIX was used to represent the ground truth. Similar to the original study, it was found that the HCM6 TTR methodology severely underestimated the TTDs, and their respective TTR metrics, on all five testbeds. This is problematic, because the HCM6 methodology indicates that the corridors had more reliable TT than the empirical data would suggest. It was also shown that the calibration methodology eliminated this underestimation. It is recommended that users of the HCM6 TTR methodology validate and, if necessary, calibrate the model using local empirical travel data.

A novel approach for vehicle travel time distribution: copula-based dependent discrete convolution

ABSTRACT Travel time reliability is considered as one of the key indicators for the performance of transportation systems. The majority of studies concerning estimating arterial travel time distribution commonly assume that the path travel time follows a certain distribution without considering segment correlation. Therefore, convolution is used. However, the assumption of independence of travel times on successive segments may not be appropriate. Recent studies showed that copulas are able to capture segment correlation. These copula models, however, are unfeasible in real-world applications. This paper proposes a novel approach using dependent discrete convolution. Path-level travel time distribution is estimated by aggregating segment-level travel time distributions using copula-based discrete convolution. This estimation is compared to the estimation of traditional convolution, a state-of-the art copula model, and the empirical distribution. It is shown that the proposed methodology produces accurate results within feasible computational time, thus, making it eligible for real-world applications.

Finite mixture survival model for examining the variability of urban arterial travel time for buses, passenger cars and taxis

Examining the travel time variability (TTV) of buses, passenger cars and taxis is essential to obtain reliable travel time in urban daily trips. TTV analyses of three travel modes are conducted using travel time data collected on two urban arterial roads in Xi'an City. Firstly, the TTV is evaluated using statistical indexes. The results reveal that the TTV differs from vehicle to vehicle, period to period and site to site. Secondly, the finite mixture survival model is proposed to address the heterogeneity of travel time data by decomposing the population into several sub-populations. Wasserstein distance and Kolmogorov–Smirnov test are used to further compare the sub-populations of different vehicle types during different periods on different roads. Finally, based on the model analysis, it can be found that the finite mixture survival model is an accurate tool to examine the variability by capturing the heterogeneity of travel time data. The difference among the sub-populations suggests different travel behaviours. It concludes that more diverse travel behaviours result in higher TTV. An accurate investigation on TTV is valuable for travellers’ mode choices and transportation management agencies to obtain reliable travel time information and improve traffic efficiency.

Calibrating the Highway Capacity Manual Arterial Travel Time Reliability Model

AbstractThe latest edition of the Highway Capacity Manual (HCM-6) includes, for the first time, a methodology for estimating and predicting the average travel time distribution (TTD) of urban stree...

Estimation of urban arterial travel time distribution considering link correlations

ABSTRACT This study proposes a pair-copula construction approach to estimate the probability distribution of urban arterial travel times from link travel time distributions (TTDs). First, link correlations are investigated and empirical evidence reveals that adjacent link travel times present multiple relationships. Then, such relationships are captured by a copula mixture model in each pair-copula associated with two connected links. Finally, the arterial TTD is derived as the product of the pair-copulas and link TTDs. The proposed approach is validated with Radio Frequency Identification Data collected from an urban arterial including four links in Nanjing, China. The results indicate that the approach can dynamically capture the positively correlated, negatively correlated, and uncorrelated relationships between link travel times. The considered competing approaches are also used to benchmark the proposed approach, and comparison results confirm the effectiveness and accuracy of the approach, especially when multistate distributions, complex correlations and limited data sample are encountered.

Grouped travel time estimation in signalized arterials using point-to-point detectors

Travel time, an essential parameter in Advanced Traffic Management Systems and Advanced Traveller Information Systems, has been studied for decades of years, especially on freeways. However, the traffic flows in signalized arterials are more complex and stochastic, which enables arterial travel times to be multistate due to the interruptions from signal controls. Therefore, the signal effects need to be considered in the estimation of arterial travel times. In this paper, a grouped travel time estimation method is proposed to consider the signal interruptions and estimate the arterial travel times on a more micro level. With the data obtained from point-to-point detectors, the method analyzes vehicles’ traffic states before signals and recognizes those vehicles sharing the same states in both upstream and downstream signals as vehicle groups. Then the estimation problem is formulated as a clustering process to recognize the vehicle groups, and the grouped travel times are represented by the centers of vehicle groups. The field tests under ten different scenarios show that the grouped travel times can capture the multistate properties of the travel times in signalized arterials and represent the observed travel times of most vehicles within minor deviations.

Arterial travel time estimation method using SCATS traffic data based on KNN-LSSVR model

In order to improve the effect of estimating travel time and provide more precise and reliable traffic information to traffic management department and travelers, we proposed an arterial travel time estimation method using Sydney Coordinated Adaptive Traffic System traffic data based on K-nearest neighbor–least squares support vector regression model. First, the virtual time series is constructed by analyzing the characteristics of the inconsistent time intervals of Sydney Coordinated Adaptive Traffic System traffic data. Second, the K-nearest neighbor method was used to search the K similarity patterns matching the current traffic pattern and obtain K travel time data. Then, the least squares support vector regression model was used to perform travel time estimation. Finally, case validation is carried out using the measured data of Sydney Coordinated Adaptive Traffic System traffic control system. The estimation results demonstrate that the travel time estimation accuracy of proposed method outperforms the other two methods.

Arterial link travel time estimation considering traffic signal delays using cellular handoff data

Link travel time is an important evaluation index of urban arterial traffic condition. It is traditionally estimated from loop detector data and GPS probe vehicle data. The former suffers from the coverage and maintenance issues. The latter has issues related to low penetration rate. Cellphone handoff data is one alternative that may address those deficiencies with its large coverage areas and continuous detection capabilities at low cost. Existing cellular probe vehicle based travel time estimation methods are primarily designed for freeway. Limited studies have been conducted for signalised arterials. Cellular handoff data detects the time lapse between two consecutive wireless handoff points. When vehicles with on-call cellphones traverse between two handoff points, their space mean speeds can be calculated by dividing the pre-calibrated distances by the time lapses. In this study, a new cellular handoff data based arterial travel time estimation model is proposed and compared with existing models. A hybrid traffic-and-wireless simulation network is built to simulate the handoff data generation and processing. Field data are collected at an arterial corridor in Chengdu, China to establish the baseline condition. The results from the proposed model show promising performance with detection errors of link travel times mostly within 10%.

Analysing driving efficiency of mandatory lane change decision for autonomous vehicles

Mandatory lane change (MLC) is a critical step in formulating global route of an autonomous vehicle on the urban road network. Improper MLC decisions on arterial roads could jeopardise efficiency (travel cost) and reliability (possibility of failed lane change). However, the existing research studies seldom investigate the optimal MLC decision at the planning level to maximise the reliability-based driving efficiency. This research aims at addressing two core strategic decision variables (MLC decision point on the road and maximum waiting time before giving up MLC). A series of simulation experiments for various scenarios are conducted for an arterial road to reveal their relationship. The results indicate that both identified decision variables inherently affect travel time spent on this road and the rate of failed MLCs, and a trade-off exists between arterial travel time and the rate of failed MLCs. Based on the simulation analysis, an analytical lane-level link performance (LLP) function is formulated to assess the impacts of MLC decisions on driving efficiency. The analysis validates that the optimal MLC strategic decision (MLC decision position and maximum waiting time) can be determined by maximising LLP function. It is promising to apply the proposed LLP function in lane-level routing algorithm in the future.

Modeling arterial travel time distribution by accounting for link correlations: a copula-based approach

The estimation of urban arterial travel time distribution (TTD) is critical to help implement Intelligent Transportation Systems (ITS) and provide travelers with timely and reliable route guidance. The state-of-practice procedure for arterial TTD estimation commonly assumes that the path travel time follows a certain distribution without considering link correlations. However, this approach appears inappropriate since travel times on successive links are essentially dependent along signalized arterials. In this study, a copula-based approach is proposed to model arterial TTD by accounting for spatial link correlations. First, TTDs on consecutive links along one arterial in Hangzhou, China are investigated. Link TTDs are estimated through the nonparametric kernel smoothing method. Link correlations are analyzed in both unfavorable and favorable coordination cases. Then, Gaussian copula models are introduced to model the dependent structure between link TTDs. The parameters of Gaussian copula are obtained by Maximum-Likelihood Estimation (MLE). Next, path TTDs covering consecutive links are estimated based on the estimated copula models. The results demonstrate the advantage of the proposed copula-based approach, compared with the convolution without capturing link correlations and the empirical distribution fitting methods in both unfavorable and favorable coordination cases.

Reconstructing Vehicle Trajectories to Support Travel Time Estimation

The primary objective of this study was to increase the sample size of public probe vehicle-based arterial travel time estimation. The complete methodology of increasing sample size using incomplete trajectory was built based on a k-Nearest Neighbors ( k-NN) regression algorithm. The virtual travel time of an incomplete trajectory was represented by similar complete trajectories. As incomplete trajectories were not used to calculate travel time in previous studies, the sample size of travel time estimation can be increased without collecting extra data. A case study was conducted on a major arterial in the city of Tucson, Arizona, including 13 links. In the case study, probe vehicle data were collected from a smartphone application used for navigation and guidance. The case study showed that the method could significantly increase link travel time samples, but there were still limitations. In addition, sensitivity analysis was conducted using leave-one-out cross-validation to verify the performance of the k-NN model under different parameters and input data. The data analysis showed that the algorithm performed differently under different parameters and input data. Our study suggested optimal parameters should be selected using a historical dataset before real-world application.

Machine Learning Approach to Decomposing Arterial Travel Time Using a Hidden Markov Model with Genetic Algorithm

AbstractBluetooth-based traffic detection is an emerging travel time collection technique; however, its use on arterials has been limited due to several challenges. In particular, data missing not ...

A novel arterial travel time distribution estimation model and its application to energy/emissions estimation

ABSTRACTArterial travel time information is crucial to advanced traffic management systems and advanced traveler information systems. An effective way to represent this information is the estimation of travel time distribution. In this paper, we develop a modified Gaussian mixture model in order to estimate link travel time distributions along arterial with signalized intersections. The proposed model is applicable to traffic data from either fixed-location sensors or mobile sensors. The model performance is validated using real-world traffic data (more than 1,400 vehicles) collected by the wireless magnetic sensors and digital image recognition in the field. The proposed model shows high potential (i.e., the correction rate are above 0.9) to satisfactorily estimate travel time statistics and classify vehicle stop versus non-stop movements. In addition, the resultant movement classification application can significantly improve the estimation of traffic-related energy and emissions along arterial.

A copula-based approach for estimating the travel time reliability of urban arterial

Estimating the travel time reliability (TTR) of urban arterial is critical for real-time and reliable route guidance and provides theoretical bases and technical support for sophisticated traffic management and control. The state-of-art procedures for arterial TTR estimation usually assume that path travel time follows a certain distribution, with less consideration about segment correlations. However, the conventional approach is usually unrealistic because an important feature of urban arterial is the dependent structure of travel times on continuous segments. In this study, a copula-based approach that incorporates the stochastic characteristics of segments travel time is proposed to model arterial travel time distribution (TTD), which serves as a basis for TTR quantification. First, segments correlation is empirically analyzed and different types of copula models are examined. Then, fitting marginal distributions for segment TTD is conducted by parametric and non-parametric regression analysis, respectively. Based on the estimated parameters of the models, the best-fitting copula is determined in terms of the goodness-of-fit tests. Last, the model is examined at two study sites with AVI data and NGSIM trajectory data, respectively. The results of path TTD estimation demonstrate the advantage of the proposed copula-based approach, compared with the convolution model without capturing segments correlation and the empirical distribution fitting methods. Furthermore, when considering the segments correlation effect, it was found that the estimated path TTR is more accurate than that by the convolution model.

Prediction of arterial travel time considering delay in vehicle re-identification

Travel time is important information for management and planning of road traffic. In the past decades, automated vehicle identifi- cation (AVI) systems have been deployed in many cities for collect ...

Estimation of delay variability at signalized intersections for urban arterial performance evaluation

ABSTRACTUrban arterial performance evaluation has been broadly studied, with the major focus on average travel time estimation. However, in view of the stochastic nature of interrupted flow, the ability to capture the characteristics of travel time variability has become a critical step in determining arterial level of service (LOS). This article first presents a stochastic approach that integrates classic cumulative curves and probability theories in order to investigate delay variability at signalized intersections, as a dominant part of the link travel time variability. This serves as a basis for arterial travel time estimation, which can be obtained through a convolution of individual link travel time distributions. The proposed approach is then applied in the estimation of travel time along one arterial in Shanghai, China, with abundant automatic vehicle identification (AVI) data sources. The travel time variability is evaluated thoroughly at 30-min intervals, with promising results achieved in comparison to the field measurements. In addition, the estimated travel time distributions are utilized to illustrate the probability of multiple LOS ranges, namely, reliability LOS. The results provide insights into how we might achieve a more reliable and informative understanding of arterial performance.

Signal Timing Detection Based on Spatial–Temporal Map Generated from CCTV Surveillance Video

Signal timing data are a critical component in the estimation of arterial traffic states. Estimating arterial travel time, intersection delay, and queue length from either detector or probe data relies on accurate input or detection of signal timing. Moreover, the emerging eco-intersection approaching and departure applications also require reliable signal timing input. With the accelerated deployment of adaptive and smart signal systems, signal timing data have become more and more readily available at arterial management centers. However, of the thousands of intersections around the country, many still do not report real-time signal timing data because of various maintenance, hardware, software, communication, cost, and other problems. Some existing studies have proposed the use of probe trajectories to infer signal timing on the basis of shock wave theory; however, because of the limited sample sizes, coverage and reliability are also limited. A computer vision–based algorithm to detect signal timing from the regular low-resolution CCTV cameras at many major arterial intersections around the United States is proposed in this paper. The algorithm detects vehicle trajectories by evaluating the movement of pixel colors at a predefined scan line on CCTV video footage. By detecting static objects on the scan line and their stalling duration, the proposed algorithm can efficiently detect the starting and ending times of red lights. The algorithm is calibrated and evaluated by using arterial traffic video collected from the intersection of Henderson Road at U.S. Hwy 1 in North Brunswick, New Jersey. The results show the promising performance of the algorithm in becoming a cost-effective signal detection solution.