ORCID

https://orcid.org/0000-0002-8865-4054

Year

2019

Season

Fall

Paper Type

Master's Thesis

College

College of Computing, Engineering & Construction

Degree Name

Master of Science in Civil Engineering (MSCE)

Department

Engineering

NACO controlled Corporate Body

University of North Florida. School of Engineering

First Advisor

Dr. Thobias Sando

Second Advisor

Dr. Priyanka Alluri

Third Advisor

Dr. Christopher J. Brown

Fourth Advisor

Dr. O. Patrick Kreidl

Department Chair

Dr. Christopher Brown

College Dean

Dr. William F. Klostermeyer

Abstract

The Florida’s Road Rangers monitor the freeways for incidents to minimize their adverse impacts on traffic. The objectives of this study were to evaluate the extent to which Road Rangers reduce incident clearance duration (ICD), incident-induced traffic delays (IITDs) and secondary crashes (SCs).

Since ICD distributions are often right-skewed, the study applied quantile regression to relate ICD to influencing factors. Data skewed to the right is usually a result of lower bounds in a data set being extremely low relative to the rest of the data. Data from 28,000 incidents that occurred on freeways in Jacksonville, Florida were analyzed. Of the factors analyzed, crash events, incident severity, shoulder blockage, peak hours, weekends, nighttime, number of responding agencies, and towing were found to associate with significantly longer ICDs. Road Rangers were found to reduce incident clearance duration by 25.3%. In other words, shorter incident clearance durations were observed when Road Rangers responded to incidents compared to other agencies.

On the second objective, IITDs were estimated by establishing incident-free recurrent travel time profiles as bases from which the incident-induced delays could be measured. To determine the extent to which Florida’s Road Rangers can reduce IITDs, the analysis was based on the data from 4,045 incidents that occurred on freeways in Jacksonville, Florida. The parametric accelerated failure time (AFT) survival model, with Weibull distribution of IITD was used to model IITDs. The results show that significant variables affecting IITDs include incident characteristics (severity, type, towing requirements, lane and shoulder blockage, etc.), Road Rangers involvement, and prevailing traffic conditions. The findings also revealed no significant effects of median width, average detector occupancy and the day-of-the-week on IITDs. A significant and unique contribution of this paper is that the Road Rangers program was found to shorten IITDs relative to other responding agencies by 12.6%.

To identify the potential impact of Road Rangers in lowering the likelihood of SCs, this study sought to evaluate the safety performance of the Road Rangers program. Since SCs are often rare, the study applied a complimentary log-log model. The analysis was based on incident data related to 6,088 incidents on freeways in Jacksonville, Florida. Of the factors analyzed, traffic volume, incident impact duration, moderate/severe crashes, weekdays, peak periods, percentage of lane closure, and shoulder blockage were found to significantly increase the likelihood of SCs. While vehicle speed and lighting condition showed little contribution (not significant at 95%) to SC likelihood, Road Rangers were associated with relatively lower probabilities of SC occurrence. Based on the reduction in the average incident duration, the results suggest that the Road Rangers reduce SC risk by 20.9%. Based on increased safety at incident scenes, Road Rangers reduce SC probability by 17.9%.

The results of this study can, in general, provide researchers and practitioners with an effective way for evaluating mobility and safety benefits of the Road Rangers program. The developed approaches provide practical guidance on how to quantify the mobility and safety impact of the Road Rangers program. The results can, in general, help practitioners to improve incident management plans.

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