BACKGROUND

Temporary traffic barriers are used to separate adjacent vehicular traffic from construction workers, work zone activity, opposing traffic, and other conditions. When errant vehicles impact temporary traffic barriers that are not anchored, the barriers can deflect (including barrier displacement and deformation) from a few inches to several feet. Workers and equipment are restricted from occupying the area behind temporary traffic barriers to avoid potential impacts with moving barriers. However, providing a clear, offset non-work zone behind temporary traffic barriers constricts the already limited work area and adds project costs.

Temporary traffic barriers must be crash tested to the same criteria (typically 25-degree impact angles and 62 mph impact speed) as other roadside devices per the Manual for Assessing Safety Hardware (MASH). However, in instances where temporary traffic control barriers are deployed, roadway widths are often narrowed, which could result in reduced vehicular impact angles. Also, where temporary traffic barriers are deployed, speed limits may vary significantly from MASH crash test speeds. 

Research is needed to develop a tool for estimating expected temporary traffic barrier deflection that considers impact angle, speed, and other factors so practitioners can determine appropriate and reasonable offset zones. While previous researchers have approached this problem by reviewing encroachment data, those studies are believed to have had limited success. Thus, modeling and evaluation are needed for potential crash scenarios involving temporary traffic barriers to estimate deflection behaviors for various roadway widths and speeds.

OBJECTIVE

The research objective is to develop a tool to estimate the deflection behavior of freestanding temporary traffic barrier systems resulting from reduced impact angles based on site conditions.

Accomplishment of the project objective will require at least the following tasks.

TASKS

PHASE I – Planning 

Task 1. Conduct a literature review of relevant research, literature, and other sources regarding the type and use of temporary traffic barrier systems as related to the project objective. The review shall include published and unpublished research conducted through the NCHRP; the Federal Highway Administration (FHWA); and other national, international, state, and pooled-fund sponsored research.

Task 2. Conduct a critical analysis and synthesis of the literature review results and identify knowledge gaps and opportunities related to the project objective. These gaps must be addressed in the final deliverables if the budget allows, or in the recommended future research. 

Task 3. Develop a method to achieve the project objective to be executed in Phases II and III. At a minimum, the method shall formulate strategies to 

• Determine the most prevalent types of temporary traffic barrier systems;
• Develop a prioritization framework for selecting temporary traffic barrier systems to be evaluated;
• Identify at least two temporary traffic barrier systems for further evaluation, one of which must be a concrete barrier system;
• Determine factors that impact barrier deflection, including vehicular speeds and offset distances between the barrier and vehicular traffic;
• Determine expected impact angles;
• Develop crash simulation model(s) using previously performed MASH crash test results for validation; and
• Develop a non-web-based tool for practitioners to estimate temporary traffic barrier systems’ total deflection. 

Task 4. Prepare Interim Report No. 1 that documents Tasks 1 through 3 and provides an updated work plan for the remainder of the research.

PHASE II – Method Development

Task 5. Develop a prioritized list of barrier systems based on the method in the approved Interim Report No. 1 and identify two systems for evaluation per NCHRP approval. At least one of the barrier systems must be nonproprietary. 

Task 6. Determine site conditions that impact barrier deflection and determine the expected impact angles using the approved method in Interim Report No 1. 

Task 7. Participate in a virtual panel meeting to discuss the findings of Tasks 5 and 6.

Task 8. Develop and validate the crash simulation models.

Task 9. Run crash simulation models for a representative sample of conditions identified in Task 6.

Task 10. Develop a mock-up of the tool for estimating the barrier systems’ deflection behavior.

Task 11. Prepare Interim Report No. 2 that documents Tasks 5 through 10 and provides an updated work plan for the remainder of the research. 

PHASE III – Final Deliverables

Task 12. Complete and finalize simulation model runs.

Task 13. Complete and finalize the tool. The draft tool is due 5 months before the end of the contract.

Task 14. Prepare final deliverables, including

• A tool to estimate temporary traffic barrier deflection;
• A research report, including an executive summary, that documents all research and project efforts;
• A PowerPoint presentation with speaker notes that summarizes the project and distinctly illustrates for the audience how the research can be applied in their organization; and
• A technical memorandum titled “Implementation of Research Findings and Products”.

STATUS: Research in progress.