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600451-00071

SWUTC Research Project Description

Quantification of Infrastructure Consumption under Different Axle Configurations and Wheel Loads

University:  University of Texas at Austin

Principal Investigator:
Jorge Prozzi
Department of Civil and Environmental Engineering
(512) 471-4771

Project Monitor:
Harold von Quintus
2003 North Mays Street
Round Rock, Texas 78664

Funding Source:  USDOT and State of Texas General Revenue Funds

Total Project Cost: $79,285

Project Number:  600451-00071

Date Started: 5/1/12

Estimated Completion Date:  6/30/13

Project Summary

Project Abstract:
Recent developments in the oil and gas energy sector in Texas have resulted in increased volumes of traffic with an associated increase in the road deterioration rate. This unanticipated and accelerated deterioration imposes additional burden on already insufficient maintenance and rehabilitation budgets that affect most state highway agencies in the United States. There is absolutely no doubt that the energy sector contributes immensely to the economy of the state and the region but it is also a fact that it is not sustainable to keep the highway system in a state of good repair. This project will attempt to quantify the problem.

The first task will consist of identifying the main stakeholders which will include state agencies, county authorities and engineers, energy industry, service industries to the energy sector, trucking industry and other relevant parties. This will enable us to assess the extent of the problem.

At the same time a mechanistically-based methodology will be developed and utilized to estimate the damage caused to the surface transportation infrastructure. We will use the DARWin-ME design guide and software. The outcome of the mechanistically-based analysis will produce the rational for establishing the proportion of damage that can be attributed to the traffic generated by the oil and gas industries and will be used to establish costs for addressing reconstruction, rehabilitation and maintenance needs. With the elements developed from the previous steps, a management system will be proposed that will enable the State Highway Agencies in the region and local authorities to make better utilization of their limited resources.

Project Objectives:
The first task will consist of identifying the main stakeholders which will include state agencies (such as TxDOT, Department of Public Safety (DPS), Texas Commission for Environmental Quality (TCEQ), Railroad Commission, the Motor Carrier Division (MCD) of the Department of Motor Vehicles (DMV), etc.), county authorities and engineers, energy industry, service industries to the energy sector, trucking industry and other relevant parties. This will enable us to assess the extent of the current problem and also to establish a system to estimate sort-, medium- and long-term developments in the oil and gas sectors.

Currently state agencies and affected counties are only implementing a reactive approach, that is, highways are repaired only after they have been damaged to an unacceptable level of service. It is well established that this approach is not optimal and it is probably the most expensive and inefficient approach. By having data on wells’ site licenses, the state and county authorities will be able to apply sound pavement management principles and make use of preventive maintenance measures.

At the same time that we will be evaluating the current situation and gathering the necessary information to estimate future developments, a mechanistically-based methodology will be developed and utilized to estimate the damage caused to the surface transportation infrastructure. As part of this task, the researchers will used the recently released DARWin-ME design guide and software. DARWin-ME is a product approved by the American Association of State Highway and Transportation Officials (AASHTO) and it is endorsed and supported by the Federal Highway Administration (FHWA). Thus, this system is deemed ideal for the current study because it can be applied to the federally-funded and the state-maintained highways systems, i.e. IH, US, SH and FM systems.

The outcome of the mechanistically-based analysis will produce the rational for establishing the proportion of damage that can be attributed to the traffic generated by the oil and gas industries and will be used to establish costs for addressing reconstruction, rehabilitation and maintenance needs.

With the elements developed from the previous steps, a management system will be proposed that will enable the State Highway Agencies in the region and local authorities to make better utilization of their limited resources.

Task Descriptions:
Task 1: Development of Potential Scenarios
This task will consist of identifying the main stakeholders as described above and to include any other relevant parties, which may include people from other states that are experiencing a similar situation. Once the main stakeholders are identified, we will contact them and meet with them to assess the extent of the current problem and also to establish a system to estimate sort-, medium- and long-term developments in the oil and gas sectors. It is anticipated that most information on future developments may be sensitive and confidential. In this case, we will have a look at the permits requested to the Texas Railroad Commission and we will establish a series of potential scenarios.

Task 2: Data Collection
The data collection task will consist of collecting all necessary data for the performance of the following tasks. These data will include:

  1. Well location and expected year of development and beginning of production
  2. Traffic associated with the (1) development and construction of the of the well and (2) operation and maintenance of the well
  3. Traffic characteristics: vehicle configuration and axle loads for the traffic associated with the development, operation and maintenance of the well site.
  4. Routing: expected routes associated with the corresponding traffic and quantification of the vehicle miles travelled
  5. Pavement structure: with the support of TxDOT personnel, we will obtain design information of the highway infrastructure that is mostly affected by the movement of traffic associated with the construction, operation and maintenance of the wells.

Task 3: Traffic and Pavement Modeling
Once the data are gathered as part of Task 2, the research team will obtain a license of AASHTO’s Mechanistic Empirical Pavement Design Guide or DarWin-ME. At least 100 different pavement structures will be modeled under two conditions: (1) subjected to expected design traffic and (2) subjected to design traffic plus the additional traffic generated by the specific energy sector. The performance will then be evaluated under three different criteria: (1) surface deformation, (2) fatigue cracking and (3) roughness.

The concept of relative performance will be used to quantify the additional damage caused by the energy sector and to calculate the reduction in pavement life. Once the pavement life reduction is obtained, an overlay will be designed for each pavement to bring it back to its original performance. The cost of the overlay will be used as an estimate for the additional infrastructure maintenance/rehabilitation cost due to the energy traffic. In order to obtain actual costs, the researcher will query TxDOT Design and Construction Information System (DCIS).

Task 4: Analysis of Results
The individual results will be processed and analyzed as part of this task. A multi-criteria optimization approach will be applied to establish the performance of the individual pavement sections evaluated. Then, the individual results will be integrated into a system that will take into account the distribution on the vehicle-miles travelled per vehicle type per facility type. Thus, at the end of the analysis, the researchers will complete a method that will used the results of the analysis to predict or estimate average costs for the state of the additional pavement consumption caused by the gas and oil sectors.
It should be emphasized that due to the budget and time constraints of this project, only the damage (generalized costs) are evaluated while the benefits will be subject of a future separate study.

Task 5: Preparation of Reports and Technology Transfer
The objectives of this task are to deliver a report documenting the research performed and to disseminate the main results of the study by submitting a paper for presentation at the next Annual Meeting of the Transportation Research Board and a prestigious relevant international transportation conference to be determined. It is anticipated that the students involved in the project will make the corresponding presentations.

Implementation of Research Outcomes:
Traditionally, pavement damage, or consumption, has been evaluated empirically by means of Load Equivalency Factor (LEF) developed primarily based on the results of the AASHTO Road Test. In this study, we developed an equivalent to LEFs but we refer to this new concept as Equivalent Consumption Factors (ECFs). The ECFs are mechanistically-based, are based in multiple failure criteria, and have a wider range of applicability. These equations that can be used to estimate pavement consumption of different heavy vehicles with different axle configurations and wheel loads. In addition, the consumption models developed as part of this research have been used as the basis for quantifying pavement consumption. These models are now being updated and will be used as part of a TxDOT Research Project (0-6817) to establish a new overweight permit fee structure in Texas.

Products developed by this research:

Published Paper:  Framework for Determining Load Equivalencies with DARWin-ME, Ambarish Banerjee, Jorge Prozzi, and Prasad Buddhavarapu, University of Texas at Austin, published in the Journal of the Transportation Research Board, Volume 2368, pp. 24-35, Washington, DC, 2013.

Models Developed: The consumption models developed by this research are being utilized by TxDOT to identify pavement-friendly vehicles and to review the current permit fee schedule.

Impacts/Benefits of Implementation:
The potential impact of the models and equations developed by this research is quite significant. They have the potential to affect pavement design, pavement management, cost allocation, safety, alternative sources of highway funding, planning and programming, etc.

The results of the study were also used in a TxDOT study that was presented to the State Legislature. It provided a better understanding to the legislators of the effects of increasing axle loads on Texas highway network. It also helped in the revision of several legislature bills and in some instances, provided TxDOT with objective tools for assessing proposed axle load increases proposed by certain industry sectors.

Web Links:
Final Technical Report