(ambient music)
- [Narrator] Guardrails are an important
and cost-effective safety feature along high-speed roadways,
shielding passenger and freight vehicles
from roadside hazards.
The end transition piece of the guardrail
is very important to the overall safety
because its purpose is to lessen the severity
of vehicle collision with the guardrail end.
The Texas Department of Transportation
supports research and development of continuous improvements
and innovations to the guardrail systems
in place across the state.
The Texas A&M Transportation Institute
developed a MASH TL-4 compliant guardrail system in 2021
and has now completed the design
and full-scale crash testing of an end transition
for the TL-4 guardrail system,
making it ready for full implementation.
- Guardrails that you see on the side of the roads
prevent vehicles from getting off the road.
They do that to prevent them from striking an object,
or crossing over to the other side,
or rolling over on a ditch.
The standard guardrail that you see on the side of the road
is designed for passenger vehicles.
There are others that are designed for freight vehicles.
So, like a single-unit truck or a tractor-trailer.
- There are locations that will have
a higher percentage of trucks.
And, so, a TL-4 system is actually
a 22,000-pound delivery truck at 56 miles per hour.
So, it's a more rigorous system
to prevent collapse of a guardrail
or whatever other type of roadside safety hardware
might be used if it's hit by a larger vehicle.
We were looking at the transition from the TL-4 system,
which is, I believe, 40 inches high,
down to the standard metal beam guard fence system
because you need a transition
because there's not necessarily an attenuator
or something that's gonna be compatible
with the TL-4 system.
So, you have the TL-4 system, which would be applied.
Then you have a transition: about a 25-foot transition,
down to the standard metal beam guard fence system,
which is TL-3.
And that way, you can utilize the system
where you think there's the greatest likelihood
that it might be impacted by a larger truck.
- For this research, we came up with different concepts
of taking the shape of the test level 4 guardrail
and morphing it gradually to your standard guardrail.
It was done here at TTI
in the roadside safety and physical security division.
We came up with different concepts.
Then, we simulated some of those concepts
using finite element simulations.
In those simulations, we looked at different impacts from,
you know, small car and a pickup truck
striking in different directions.
And we were trying to assess the safety
of that transition portion of the guardrail.
We did a lot of iterations on the design,
the initial concepts that we had,
until we came up with something
that we felt was worthy of testing,
and we felt good about it working well in crash testing.
We performed two tests.
Both of those tests work very nicely, and as a result,
we have a very nice transition design.
- [Kenneth] There are a lot of trucks in Texas,
and for areas that we want to provide
a greater degree of protection with high-percentage trucks
in maybe a more economical way,
this system will be very beneficial in that area.
- [Narrator] For more information
and to find the publication for this project,
please visit the TxDOT Research Library
at the link shown below.