Description:
There are thousands of miles of concrete barrier in place on the highways across the United States and many more miles used as temporary barriers in work zones. There are 5 typical concrete barrier shapes which have been used for years that generally have performed acceptably. The different shapes with their different design characteristics provide some tradeoffs with crash performance. It is well understood that the safety shape design incorporated to a varying degree in 4 of the designs cause the vehicle to ride-up the barrier face which dissipate kinetic energy. This can also be a contributing factor to vehicle rollover for lower angle crashes. The vertical wall that does not incorporate this safety shape (sloped faced) also performs acceptably but it increases the forces on occupants, lateral forces on the wall and under some conditions result in a high risk crash called head slap, where the occupants head makes contact with the wall which is usually fatal.
Recent research has identified there is a need to improve concrete barrier performance since the more commonly used safety shape designs have a tendency to induce vehicle rollover which can also be a very severe crash. The Midwest Roadside Safety Facility (located at the University of Nebraska) developed a better performing barrier that addressed the issues but to incorporate the features from this design would require reconstruction of the many thousands of miles of barrier. Other research performed by Texas Transportation Institute and published in NCHRP 554 showed that increased surface friction along the barrier face enhanced the rollover problem and warns exceeding a threshold. Subsequent unpublished barrier simulation by NCAC for FHWA showed that reducing the friction along the sloped surface reduces the rollover tendencies of TL-3 vehicles. Some limited testing was performed at the Texas Transportation Institute by impacting a bogie vehicle into portable concrete barriers coated with epoxy sealant (epoxy has extremely low friction properties and sometimes used to simulate ice for skid test). The coatings were not tough enough to withstand the impact and the results showed no benefits.
Therefore, to improve the performance of existing barriers and reduce vehicle rollover crashes, a coating, or other surface treatment for existing, in-place concrete barriers is sought that would provide a durable low friction material and, thereby, reduce the rollover potential of vehicles striking barriers. To be successful, the coating (or other surface treatment) should be:
1. The product should be low cost and easily installed in a traffic environment
2. Durable in an impact so performance is not reduced
3. Resist sunlight degradation
Expected Phase I Outcomes:
Outcomes expected from Phase I include a detailed concept that demonstrates the viability of creating a prototype that satisfies the issues identified above. Also a marketing strategy that anticipates the crashes that could be reduced and a possible deployment strategy based on a cost benefit approach.
Expected Phase II Outcomes:
Phase II outcomes may include identifying or developing a product and crash testing to verify product performance and durability. A field application under controlled conditions would be necessary to demonstrate ease of installation and test sections applied in real world conditions to demonstrate to the market the viability of this approach.
