(gentle music)
- [Narrator] With freight traffic on the rise
TxDOT wanted to ensure that motorists
are as safe as possible especially in corridors
where freight and truck traffic is the highest.
Meeting Test Level 4 standards with metal guardrail systems
has never been attempted until now.
- You'll commonly see our guardrails on the side of highways
and those guardrails are are meant to protect motorists
from getting off the road.
- A high percentage of, you know,
serious accidents and fatalities are associated
with the driver leaving the roadway,
not necessarily an impact with another vehicle.
So yes, they do save a lot of lives on a yearly basis
and TxDOT literally has thousands of miles
of metal beam guard fence in the state.
Texas has a lot of heavy trucks as well as we have
a pretty substantial Texas highway freight network.
Typically most guardrail is tested
to what's called Test Level 3
which basically means 62 miles per hour
for a 5,000 pound pickup.
But Test Level 4 takes it up a notch
and basically this is a 22,000 pound delivery type truck
that is tested at 56 miles per hour.
Obviously that's gonna have a lot more kinetic energy.
And so the intent is to have a more durable guardrail
for those high truck traffic and freight network areas.
- Texas already has a lot of concrete barriers
that provide the same level of containment
for freight trucks, but this is a metal guardrail
and there are several benefits to having a metal guardrail.
It's expected to be cheaper than a concrete barrier,
it's more open design on highways.
We will also be able to transition much easier
from this guardrail to a standard guardrail
which is not Test Level 4 guardrail
which is why Texas wanted to have this design
as one of their standards.
- [Kenneth Mora] There were various alternatives
that were looked at and the final alternative
that was selected basically is about 40 inches tall,
so it's a little taller than the standard guardrail
and at the top, it has a box beam type element
to assist in the absorption of energy.
- [Nauman Sheik] We were trying to use as many components
of existing hardware that Texas uses.
There's a benefit to doing that.
They're able to use the same hardware,
they don't have to inventory a lot of different hardware.
We did very detailed computer simulations
where we were impacting these guardrail design
with different vehicles, as we would do later on in testing.
Once we were satisfied with the design
that it's working the way we want it to
then moved on to a full-scale crash testing.
On this guardrail we performed three different tests.
The first test was with a freight truck.
It's basically a single unit truck.
It weighs about 22,000 pounds.
We also tested with the small car and the pickup
which were also contained and redirected by this barrier.
- [Kenneth Mora] We'll start developing
a roadway design standard for this particular unit
and provide guidance on it's application,
what recommended application areas in the standard.
There will be a new standard related
to the TL... for a metal beam guard fence system.
- [Narrator] For more information
and to find the publications for this project,
please visit the TxDOT Research Library
at the link shown below.