NS728 - Research & Innovation

NS728: High Tension Cable Median Guardrail Expected Lifespan

Problem

MnDOT has been installing High Tension Cable Barrier (HTCB) Systems for approximately 20 years along our heavily travelled corridors. While there have been studies on location and proper installation of HTCB as well as crash-test studies on these systems, little is known with regards to life expectancy and inspection of existing systems.

Objective

There is a need to understand the life of HTCB systems and the inspection process for this critical safety equipment. Impacts to the anchor blocks and cables due to aging, weathering, and crashes as well as overall lifespan are unknown. When these unknowns are compounded, it potentially increases the risk to the travelling public as well as MnDOT maintenance staff. MnDOT has identified the following research questions to address for the proposed research:

Does an aging HTCB system still function as designed?
Are there elements that need replacing based on number of crashes in the system?
Do frontline employees called upon to repair these systems face increased safety risk?
What should be considered a typical lifespan for a system and how will that factor into planning and design resources?

Previous research

Previous research discovered has seemed to mostly focus on design, maintenance, and cost benefit of HTCB usage. No research appears to have been completed on the total lifespan of a HTCB system and how age, elements, and traffic crashes impact the long-term effectiveness of a system.

Expected benefits

The numbers 1 and 2 indicate whether the source of the benefit measurement is from:

A specific research task in your project that supports measuring this particular benefit, or
Implementation of the research findings (anticipating positive results)

Decrease Engineering/Administrative Cost: (2)
- Better understanding of lifecycle of these systems will allow for better long-range planning and funding for replacement when systems come of age.
Increase Lifecycle: (2)
- Understanding the lifespan of these systems will ensure that motorists are better protected should they find themselves leaving the roadway.
Operation and Maintenance Saving: (1)
- Understanding lifespan and frequently encountered issues provides better understanding of where focus should be on repairing systems vs replacing systems.
Safety: (2)
- Reducing the unknowns described above could provide for better techniques during repair. A better understanding can help our employees better understand the risks involved and improve safety. Systems that are within the lifecycle may provide more stable safety benefits for road users should they encounter a crash.
User Benefits: (1)
- With a better understanding of overall lifecycle of these systems, employees will have the knowledge of how to approach aging systems.
Risk Management: (2)
- Assuring systems are not out of lifecycle which can expose employees to additional safety hazards while repairing the guardrail that is damaged.
Better understanding of each vendor's systems: (1)
- Three vendors currently provide these systems to MnDOT. A better understanding of how each system reacts and ages may help us moving forward with ensuring we are employing the best.

Expected outcomes