Pilot Testing of SHRP 2 Reliability Data and Analytical Products: Florida

Hadi, Mohammed; Xiao, Yan; Wang, Tao; Hu, Pei; Jia, Jianmin; Edelstein, Robert; Lopez, Alexandra

doi:10.17226/22331

Cited by 3 publications

(3 citation statements)

References 1 publication

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“…The latest version of HCM comes with a revised method to generate reliability scenarios and calculate performance metrics, primarily TTI distributions. However, validations conducted as part of the SHRP 2 L08 project revealed that the observed capacity values in the field were usually lower than the proposed values in the manual (26)(27)(28)(29)(30).…”

Section: Literature Reviewmentioning

confidence: 88%

Validation and Calibration of Freeway Reliability Methodology in the Highway Capacity Manual: Method and Case Studies

Karmakar

Aghdashi

Rouphail

et al. 2018

Transportation Research Record: Journal of the Transportation R

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Traffic congestion costs drivers an average of $1,200 a year in wasted fuel and time, with most travelers becoming less tolerant of unexpected delays. Substantial efforts have been made to account for the impact of non-recurring sources of congestion on travel time reliability. The 6th edition of the Highway Capacity Manual (HCM) provides a structured guidance on a step-by-step analysis to estimate reliability performance measures on freeway facilities. However, practical implementation of these methods poses its own challenges. Performing these analyses requires assimilation of data scattered in different platforms, and this assimilation is complicated further by the fact that data and data platforms differ from state to state. This paper focuses on practical calibration and validation methods of the core and reliability analyses described in the HCM. The main objective is to provide HCM users with guidance on collecting data for freeway reliability analysis as well as validating the reliability performance measures predictions of the HCM methodology. A real-world case study on three routes on Interstate 40 in the Raleigh-Durham area in North Carolina is used to describe the steps required for conducting this analysis. The travel time index (TTI) distribution, reported by the HCM models, was found to match those from probe-based travel time data closely up to the 80th percentile values. However, because of a mismatch between the actual and HCM estimated incident allocation patterns both spatially and temporally, and the fact that traffic demands in the HCM methods are by default insensitive to the occurrence of major incidents, the HCM approach tended to generate larger travel time values in the upper regions of the travel time distribution.

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Section: Literature Reviewmentioning

confidence: 88%

Validation and Calibration of Freeway Reliability Methodology in the Highway Capacity Manual: Method and Case Studies

Karmakar

Aghdashi

Rouphail

et al. 2018

Transportation Research Record: Journal of the Transportation R

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“…There are other studies on the details of the incident's effect on freeway capacity (11). Several agencies have tested the travel time reliability method on several facilities (12)(13)(14)(15)(16). A study in North Carolina modeled three routes on I-40 in the Raleigh-Durham area and predicted the travel time indices (TTIs) reported by HCM modeling within the 80th percentile of true probe-based data (16).…”

Section: Capacity Effect Of Incidentsmentioning

confidence: 99%

Evaluating the Effect of Incidents on Freeway Facilities and Updating the Incident Capacity Adjustments for HCM

Addison

Aghdashi

Rouphail

2020

Transportation Research Record: Journal of the Transportation R

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This paper investigates the effect of incidents on freeway segment capacity. Currently, the Highway Capacity Manual (HCM) provides a look-up table linking the remaining segment capacity fraction during an incident to the total and closed number of lanes on the segment. In reality, segment capacity during an incident will tend to vary over time, with the most severe effects felt early on before any type of response is initiated, with congestion progressively improving as the appropriate incident management actions are implemented. By applying a genetic algorithm calibration method on each incident day and calibrating the incident capacity adjustment factors (CAFs), optimal time-dependent CAFs were derived that best represented the effect of incidents on the freeway segment capacity. By analyzing the optimal CAFs, the strongest relationship was revealed to be between the optimal time-dependent CAF and the temporal progression of the incident. A regression model was developed to represent this behavior. This was formulated in a manner that can directly adjust the current HCM’s fixed CAF values (for a specific lane closure configuration) for modeling incidents both in single day, seed file application, or for an entire year reliability analysis. A portion of WB I-540 in Raleigh, NC was selected as the study area in which the proposed method was tested. Between January 2014 and December 2018, the team identified 22 isolated incidents (away from the recurring congestion period) that closed one or two lanes of traffic, creating a distinct congestion pattern.

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“…List et al showcased the L02 product by applying it in building a TTR monitoring system for several states ( 6 ). The method takes non-recurrent congestion factors into consideration and is able to identify the cause and location of unreliability, demonstrating its advantages over other single-value measures ( 9 – 11 ). However, very few studies have been conducted to assess the effectiveness of reliability analysis with this method.…”

mentioning

confidence: 99%

Validating the Adaptability of Travel Time Reliability Measurements using Probe Data

Chen

Liu

Farnsworth³

et al. 2019

Transportation Research Record: Journal of the Transportation R

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Travel time reliability (TTR) is considered a critical piece of information in highway performance evaluation. The L02 project from Strategic Highway Research Program 2 (SHRP2) has developed a holistic method using statistical probability functions of travel time as the TTR measure to build highway performance evaluation and monitoring systems. Compared with single-value reliability measures, the L02 measure is able to identify sources of unreliability and quantify their associated impacts. To validate the adaptability of L02 measure, TTR analysis on the I-15 freeway corridor in Salt Lake City, Utah using probe data has been conducted. The result is compared against output from the quadrant-based TTR measure that is currently used by the Utah Department of Transportation. Through cross-validation, it is determined that the two suites of measures demonstrate good consistency in relation to reliability assessment and unreliability source diagnoses. In addition, the study provides a method to calibrate the quadrant-based TTR measure, and new critical values were developed based on the cross-validation.

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Pilot Testing of SHRP 2 Reliability Data and Analytical Products: Florida

Cited by 3 publications

References 1 publication

Validation and Calibration of Freeway Reliability Methodology in the Highway Capacity Manual: Method and Case Studies

Validation and Calibration of Freeway Reliability Methodology in the Highway Capacity Manual: Method and Case Studies

Evaluating the Effect of Incidents on Freeway Facilities and Updating the Incident Capacity Adjustments for HCM

Validating the Adaptability of Travel Time Reliability Measurements using Probe Data

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