FHWA and AASHTO release findings on dimensions of ET-Plus guardrail end terminal
The Federal Highway Administration (FHWA) and the American Association of State Highway and Transportation Officials (AASHTO) today released the findings of a joint task force which evaluated field measurement data collected by FHWA engineers from more than 1,000 4-inch ET-Plus devices installed on roadways throughout the country.
FHWA and AASHTO together formed two joint task forces in early 2015 to examine some of the allegations about the ET-Plus guardrail system. The report released today includes the findings from the first joint task force, which aimed specifically to further investigate allegations of multiple versions of the ET-Plus, and whether the devices used in recent crash tests are representative of the devices installed on roads.
The joint task force concluded the following:
- There is no evidence to suggest there are multiple versions (i.e., ET-Plus 4-inch devices with markedly different dimensions) on our nation’s roadways.
- The end terminals crash tested at the Southwest Research Institute (SwRI) between December 2014 and January 2015 are representative of the devices installed across the country.
“Our objective is to determine if the ET-Plus performs as designed to keep motorists safe in the event of an accident,” said FHWA Deputy Administrator Gregory Nadeau. “The data and the conclusions of this task force clearly indicate that the devices recently tested are representative of the ET-Plus devices on the nation’s roadways, and that the results of those tests can and should be used as part of our comprehensive process to evaluate the safety and performance of the ET-Plus.”
“Safety is the top priority of state departments of transportation,” said Bud Wright, AASHTO Executive Director. “In the end the data will determine if the ET-Plus meets the standard required of roadside safety devices.”
In response to allegations that versions of the ET-Plus with varying dimensions had been manufactured, sold and installed on the roads and that the devices recently crash tested were not representative of the ET-Plus devices installed on the nation’s roadways, a team of engineers from FHWA undertook the task of measuring guardrails across the country. Between November 2014 and January 2015, FHWA engineers examined and measured multiple dimensions on ET-Plus devices across the country.
FHWA engineers collected measurements of 1,048 ET-Plus devices in five states — Arizona, California, Illinois, South Carolina and Texas. FHWA engineers took measurements of several aspects of the device, including the exit gap and the channel height where it enters the head of the end terminal. The data do not support the assertion that there are multiple versions of the device. In addition, the measurements of the devices that were recently crash tested are all within the dimensions represented in the sample. The measurements and sample size indicate with 98% confidence that the sample in this report represents the devices on the nation’s roadways.
The FHWA-AASHTO Task Force on the Trinity ET-Plus Guardrail Dimensions report is posted at http://www.fhwa.dot.gov/guardrailsafety/dimensionsreport.pdf. The data that were collected and reviewed by the task force are posted with the report. That data contains the location of each device that was measured and each device’s measurements.
A second joint task force is reviewing a broad range of crash reports from multiple sources to determine if the ET-Plus has potential vulnerabilities that could compromise its ability to perform as designed. FHWA and AASHTO will make that task force’s conclusions public once its analysis is complete.
On Feb. 6, 2015, FHWA released the results and an analysis of four crash tests conducted by SwRI on the Trinity ET-Plus guardrail end terminal at a height of 27-¾ inches; FHWA concluded the device met the appropriate crash test criteria followed by the States. The crash test results, as well as the reviews and analyses by FHWA, SwRI and Dr. Clay Gabler, an independent expert, are posted at http://www.fhwa.dot.gov/guardrailsafety/. The results and analysis of the four crash tests conducted by SwRI on the Trinity ET-Plus guardrail end terminal at a height of 31 inches are being reviewed and will be released shortly.
