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600451-00069

SWUTC Research Project Description

Development of an Interactive GIS Based Work Zone Traffic Control Design Tool

University:  University of Texas at Austin

Principal Investigator:
Randy Machemehl
Department of Civil and Environmental Engineering
(512) 471-4541

Project Monitor:
Tracey L. Friggle
P.E. Director of Construction
Dallas District
Texas Department of Transportation

Funding Source:  USDOT and State of Texas General Revenue Funds

Total Project Cost: $79,285

Project Number:  600451-00069

Date Started: 5/1/12

Estimated Completion Date:  6/30/13

Project Summary

Project Abstract:
This study will develop a methodology for enabling sub-network analyses in the context of a large network Dynamic Traffic Assignment (DTA) model. DTA tools are currently being applied to large urban networks and they provide the best available methodology for identifying network implications of temporary capacity changes, such as work zones, to selected links. However, the computational burden of DTA application for a large network is extreme requiring days for completion and the typical work zone analysis gains very little from a complete network analysis.  A sub-network analysis tool would enable DTA application for work zone capacity disruptions but would perform the traffic assignment only for the partial network that is likely affected with much less computational burden and vastly improved response times. This effort will include developing a methodology on a prototype network, testing that methodology, and creating an algorithm for implementation. For full-scale implementation, an existing DTA network model, probably the Dallas, Texas network will be used to provide consistency with the Dallas District Traffic Control Planning (TCP) GIS tool. Ultimately, it is intended that the GIS tool and the DTA model be linked to establish a seamless process of importing and exporting information between the two software programs, as required to complete a TCP evaluation. It is intended that roadway capacity changes be input into the GIS tool by the user and this information be exported to the DTA model. The sub-network tool will feed the DTA model that will be run to provide analysis outputs, including link volumes and speeds for the affected area. This information will be converted into travel times, delay, and level of service information within the GIS tool to provide user-friendly feedback for completing the TCP assessment.

Project Objectives:
The primary objective of the study is to update the DTA model for the DFW area with the capability of subnetwork analysis. This will involve developing a methodology on a prototype network, testing that methodology, and creating an algorithm for implementation. For full-scale implementation, the existing DTA model will be verified to ensure all applicable roadway links are included, primarily in the Dallas network to provide consistency with the Dallas District GIS tool. The study will also involve updating the GIS tool with additional links to make sure the entire TxDOT network is incorporated. Ultimately, it is intended that the GIS tool and the DTA model be linked to establish a seamless process of importing and exporting information between the two software programs, as required to complete a TCP evaluation. It is intended that roadway capacity updates continue to be input into the GIS tool by the user and this information be exported to the DTA model, along with the surrounding area required for the subnetwork analysis. Next, the subnetwork of the DTA model will be run to provide analysis outputs, including link volumes and speeds for the affected area. Finally, this information will be converted into travel times, delay, and level of service information within the GIS tool to provide user-friendly feedback for completing the TCP assessment.

Task Descriptions:
Task 1: Literature Review
Perform a comprehensive review of relevant literature associated with DTA modeling, as well as subnetwork analysis. This will include investigating literature relative to subnetwork analysis for static traffic assignment models, including capacity constrained, volume constrained, and all-or-nothing strategies. The literature review will involve the investigation of incorporating subnetwork analysis within the DTA framework and implementing an algorithm to automate the process.

Task 2: Developing a Prototype Network
Create a sample network for a DTA model in order to test the feasibility of implementing a subnetwork analysis. This task will involve setting up a time-dependent trip table (or Origin-Destination (O-D) matrix), test study period, and the network information, including number of lanes on each link and connectivity for the sample network.

Task 3: Testing the Methodology
Develop at least two concepts for implementing the subnetwork analysis strategy in the DTA model created for the sample network. This will involve thoroughly investigating methodology developed for static traffic assignment models. These methods will involve modifying the O-D matrix to account for paths outside of the subnetwork while maintaining a focus on links within it. It will also involve looking at the strategy of utilizing a sketch network, and the trade-offs associated with the increased computational speed and decreased accuracy with using a less detailed network. Overall, the strategies will be evaluated to determine which methodology provides the best results while maintaining computational efficiency.

Task 4: Developing an Algorithm
Develop an algorithm based on the results from testing the methodology previously developed and tested for the prototype network. The algorithm will be formulated using input obtained from the literature, as well as consultation with faculty members who have expertise in this area. This will involve looking closely at automating the process of modifying the O-D matrix for the full network into a smaller version for the subnetwork or sketch network.

Task 5: Updating the Networks
Update the DTA model of the DFW area to make sure all of the required links are created and the associated information is current, particularly with respect to the Dallas area portion in order to maintain consistency with the GIS tool. Update the network in the GIS tool to ensure that the entire TxDOT roadway network is included.

Task 6: Implementing the Strategy
Code the software algorithm for the chosen subnetwork analysis concept into the DTA model software. Using the smaller prototype network will be required to verify that a working algorithm has been developed to automate the process and before a large-scale implementation on one or more real-world networks is completed.  This will involve determining the size and nature of the subnetwork to be analyzed using the developed methodology.

Task 7: Testing the Algorithm
Evaluate the capability and results obtained from implementing the subnetworking algorithm on the prototype network. Particular attention should be paid to the automated process of updating the O-D matrix for the paths outside of the subnetwork, as well as within it, and successful traffic assignment based on this modified matrix. This will be validated by comparing the results of the subnetwork analysis versus those obtained for the full network DTA model based on a measure of effectiveness, such as a volume comparison using root-mean-square error. Upon successful completion of the process on a sample network, a larger real-world network can be tested and validated in a similar manner.

Task 8: Linking the Software Tools
Develop a link between the DTA model and subsequent network with the GIS tool. This should include taking modifications to the roadway network and traffic volume information entered into the GIS tool, as well as the subnetwork area to be analyzed, and transferring this as input into the DTA software. This will also require the output information from the DTA model analysis of the subnetwork, including travel demand and speed information, to be transferred back to the GIS tool to provide feedback to the user. It is intended that this feedback be user-friendly, including information about travel delay and level-of-service, thus enabling a comprehensive assessment of predicted traffic impacts resulting from a TCP.

Task 9: Reports
A comprehensive report documenting all work, discoveries, code and findings will be developed. At least two papers will be offered and presented to national organizations as a means of sharing the new technology developed through the study.


Implementation of Research Outcomes:
This project developed a traffic control planning tool package to enable smarter planning of work zone traffic control schemes and demonstrated how available technology can be incorporated by most transport agencies to produce a similar took kit.  The package brings together elements of geographic information systems (GIS), data bases containing geometric characterizations of roadways, traffic volume data and traffic control information.  The resulting package provides users with a conveniently available tool for developing or checking work zone traffic control plans.

The results have already been shared with the Dallas TxDOT district and we anticipate application of the technology by that agency and potentially other State DOT entities.

Impacts/Benefits of Implementation:
The work zone planning tool kit will provide a convenient way for public agencies to plan construction activities to minimize highway user costs and improve safety.  This will reduce societal costs of highway construction and re-construction activities.  As much of the current highway infrastructure is reaching the end of its design life, extensive renovation will be required in coming years and this package can play a key role in making renovation projects user tolerable.

Web Links:
Project Technical Report