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(dramatic music)

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- [Narrator] Roadway designers
use safety prediction models

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to evaluate the effectiveness
of roadway safety features.

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The Texas Department of Transportation

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with help from the Texas
A&M Transportation Institute

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recently refined these models

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for use on roadways as wide

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as 12 lanes or for freeway managed lanes.

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Researchers also updated
local calibration factors

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in the models and developed
an analysis tool to

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help practitioners who use them.

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- There's a document called
the Highway Safety Manual

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which contains models to
estimate the crash frequency

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that you would expect

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for roadways of different types, and some

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of the most recent material
was getting a little old

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maybe five, 10 years ago.

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It was developed

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and most importantly
was developed using data

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from other states.

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So our goal here was to
calibrate those models

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to Texas conditions.

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Looking specifically at urban freeways.

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- So there are certain limitations

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to the Highway Safety Manual

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especially highway safety
manual predictive method.

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And these three limitation include

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like maximum number of lanes,
freeways with managed lanes,

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the average interval traffic or AGT.

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So Tex DOT has been
developing major projects

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where we have 10 plus lanes.

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We have free lanes with managed
lanes and also higher AGT.

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So it would be logical to
develop new models where

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we address the Highway
Safety Manual limitation

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as well as calibrate these
models to the Texas condition.

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- Specifically, there is interest

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in estimating crash frequency

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on urban freeways with managed lanes,

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high occupancy vehicle
lanes, toll lanes, et cetera.

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That required us to collect data

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for segments on these
types of roadways in Texas.

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In the case of managed lanes

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that meant developing new models and

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for just conventional
urban freeways, we had to

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compare what the Highway
Safety Manual was predicting

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for crash frequency and what
we were actually observing

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in our sample of segments.

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One of the key things
we did in this project

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was we developed a
spreadsheet program where

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the analyst can just
enter the input data to

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describe the facility
that they're evaluating

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the traffic volume, the number of lanes,

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the cross sectional widths,
the presence of ramps

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and so forth.

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That makes it easier

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for them to apply the
Highway Safety Manual

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without having to do it the hard way

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with a calculator and working
through the equations by hand.

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- The findings from this study, you know

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will be used by Tex DOT designer
to develop a safer design

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and provide more reliable
information to decision makers

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and hopefully the findings
will enhance the knowledge

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and fill the gaps in the knowledge

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and improve the knowledge to
improve the infrastructure

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not only within Texas, but
also across the United States.

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- [Narrator] For more information

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and to find the publications
for this project,

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please visit the Tex DOT research library

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at the link shown below.