(logo whooshing)
- [Narrator] Texas motorists are safer
thanks to roadside barriers
that keep vehicles from leaving the roadway.
W-beam median guardrail barriers,
and median concrete barriers both work well by themselves.
But when the two systems are joined,
it's that transition space that has not been mass approved,
until now.
- Any time we transition from one type of barrier to another
that has big differences in deflection,
it's important to have a gradual transition
to keep the public safe.
And this project specifically addresses the transition
from double-sided guard rail to a rigid concrete rail.
- We do have two mass crash tested devices,
which is the double-sided, double-beam guard rail,
and then we do have the concrete barrier.
However, we don't have the connection tested between them,
how you transition between one to the other.
And that is not a simple task to do.
We have to make sure the transition
is really as safe as possible
without any safety or performance issue.
- [Chris] The double-sided guard rail
is much cheaper to install than the concrete barriers.
Districts might not have the funds to install concrete
all the way down,
but they might have enough funds to install
double-sided guard rail.
Also, double-sided guard rail allows
for drainage underneath,
which concrete barriers do not allow for enough drainage.
This project allows us to make that choice
and to make the best choice for the public.
- [Akram] Then you want to have the stiffness
to be kind of matching
going from the medium W beam to the concrete.
And that's where you start having a double W beam
meaning is you're going to have four W beam
nested in one side, nested in the other side.
And then even for the tires, they come down,
they're going to be engaging the face of the concrete.
So you want to have a rub rail.
So that's another W beam down there
that just kinda makes sure the tires don't engage
with the post as well.
And the posts will be increased.
So instead of have post at 6'3",
they can be down to half of that, 3' 1/2" frequency.
And you keep going with, that to even a quarter frequency.
So with that, your stiffness is gonna be more like,
this much and you're gonna go this much,
this much until you go to very stiff concrete,
and ensure you have a really smooth transition.
- [Chris] A full scale crash test in this instance,
showed us that this transition was going to be
safe for the public, anywhere that it's impacted.
- The test is basically you want to target
the critical point.
And because you have transitioning and have critical points,
and these will be for the truck, as well for the small car.
So there are two cars, two trucks,
and three critical points there that we test at.
And they're all under MASH.
Now, all the tests were done
at a hundred kilometers an hour, 60 miles per hour.
At 25 degree impacting.
- [Chris] From here, TxDOT will develop a standard,
and we'll distribute the standard to our districts,
and make the designers aware of it's availability.
And that it is MASH compliant,
and it has been tested in accordance with MASH.
(truck crashing)
- [Narrator] For more information,
and to find the publications for this project,
please visit the TxDOT research library
at the link shown below.