Validation of the Highway Capacity Manual Urban Street Travel Time Reliability Methodology using Empirical Data

Abstract

The 6th edition of the Highway Capacity Manual (HCM-6) includes the concept of travel time reliability (TTR), which attempts to determine the distribution of average trip travel times over an extended period. TTR is an inherent part of travelers’ route choice decisions and is used by traffic managers to better quantify operations rather than simply using average travel times. The focus of this paper is on the HCM-6 urban street TTR methodology contained in Chapter 17. The approach uses historical data (e.g., weather and volume fluctuations) and simple empirical data (e.g., 1-day volume count) to provide the user with average travel time and reliability predictions for a traffic facility over an extended period (e.g., a year). To the best of the authors’ knowledge, there is no existing literature on validating the HCM-6 methodology with empirical data. The goals of this paper were to validate the HCM-6 urban street reliability methodology by comparing the empirical Bluetooth (BT) travel time distributions with the estimated HCM-6 distribution, and to propose potential HCM-6 augmentation strategies. Archived BT data from a 0.5-mi urban arterial in Lincoln, Nebraska was used for comparison. It was found that there were statistically significant differences, but minimal practical differences, between the mean of the predicted HCM-6 travel time distribution and the mean of the empirical distribution. However, the HCM-6 distribution had a lower variance than the empirical distribution. Not surprisingly, the HCM-6 model underestimated the TTR metrics (buffer index and the planning time index) by approximately 62% and 9%, respectively.

Calibrating the Highway Capacity Manual Arterial Travel Time Reliability Model

“…In other words, the HCM-6 TTR metrics indicated that the testbed was more reliable than field measurements would indicate. Similar results were also shown on a 0.8-km (0.5-mi) testbed in Lincoln, Nebraska (Tufuor and Rilett 2019).…”

Bluetooth Verisi Kullanarak Kentsel Arterlerde Seyahat Süresinin Değerlendirilmesi

“…BT-based traffic data has been frequently used in traffic analysis due to the higher sampling rate and low cost [12]. While some studies focused on the reliability of travel times for freeways or urban arterials [3][4][5][6][7][8][9][10], some other studies focused on the estimation of origindestination matrix [2,[13][14][15], freeway performance evaluation [10,[16][17], traffic safety analysis [18], delay estimation for signalized intersections [19][20][21]. Since the focus of this study is to examine the reliability of TT data, it is useful to present the TT related studies in this section.…”

“…As for literature on the Bluetooth-based studies, the accuracy or variability of the travel times has been investigated particularly for freeways or multilane highways [3][4][5][6][7], whereas there were limited studies regarding the travel time reliability for urban arterials controlled with traffic signals [8][9][10] which is the main focus of this study. For this purpose, BT-based travel time data was collected for two days (October 8-9, 2019) during morning peak hours (07:30-09:30) from five consecutive intersections located on major urban arterials in Mersin, Turkey.…”

Analysis of Component Errors in the Highway Capacity Manual Travel Time Reliability Estimations for Urban Streets

“…Bluetooth detectors have been installed in the traffic cabinets for collecting empirical point-to-point Bluetooth travel time (BT) data. A comprehensive analysis of the BT data collection system, its filtering algorithm, and a validation process are provided elsewhere (11). The BT sampling rate was from 4% to 6%, which falls within the detection range of similar travel time studies (12)(13)(14).…”