BACKGROUND

Iowa Department of Transportation (IDOT) chose to install 

their introductory HFST application on a bridge over the Cedar 

River. The 5-in-1 structure comprises four bridges: north and 

southbound I-380, eastbound “A” Avenue, westbound “F” Avenue, 

and a dam. Located just west of the river, the curve is a part of the 

six-lane urban I-380 that runs through Cedar Rapids and carries 

approximately 85,000 vehicles per day. Several large corporations 

surround this area and ship supplies nationwide, contributing to 

the approximately 7,800 heavy trucks that use the bridge daily.

There are multiple factors that contribute to the crash risk at this 

location. Several ramps feed traffic onto I-380 in close proximity 

to one another, forcing vehicles to make quick lane changes. In 

addition, the travel speeds were excessive for the curve radius and 

existing pavement friction. As a result, drivers, maintenance staff, 

and police officers frequently reported that the bridge deck was 

slick, especially when wet. 

These factors contributed to more than 54 crashes reported 

between the spring of 2008 and the spring of 2012, of which 28 

were injury crashes. The crashes caused significant traffic delays 

due to high traffic volumes on the bridge. Eight of the 54 crashes 

involved a semi-trailer, one of which caught media attention 

when it toppled over the side of the bridge and caught fire below. 

To further evaluate the crash causes and explore potential 

solutions, IDOT conducted a road safety audit (RSA) at this location. 

During the field reviews, friction tests indicated skid numbers in 

the 30s and 40s. To address the pavement friction issues, the RSA 

team recommended HFST as a possible countermeasure.

FACTORS AFFECTING HFST SELECTION

IDOT staff considered and compared multiple pavement friction 

restoration technique solutions that would reduce crashes significantly and quickly. One potential solution was shot-blasting, which 

may temporarily increase friction values into the low 60s. IDOT also 

considered repaving this portion of I-380, but the expense was 

greater than available funding. Further, the new surface could have 

polished quickly due to the high traffic volumes, volumes of heavy 

trucks, and frequent lane changes just as the existing pavement 

had experienced. 

CASE STUDY

IOWA

I-380, Cedar Rapids

HIGH FRICTION SURFACE TREATMENT (HFST)

High friction surface treatments (HFST) are an effective countermeasure for improving pavement friction to meet friction demand 

at curves on both asphalt and concrete surfaces. HFST can increase friction values on bridge decks far above those achieved by new 

asphalt or concrete, as well as extend its lifespan. 

High Friction Surface Treatments: Not Just for Rural Curves

Figure 1. 5-in-1 Cedar Rapids Bridge

GOOGLE MAPS

Photo: Thinkstock item 177503855 Bridge in Cedar Rapids, Iowa 
Also, IDOT were not aware a documented history of successfully 

applying HFST to bridge decks in states with cold climates. To 

convince their staff of its merits, IDOT installed HFST on their 

office campus grounds to observe the installation process and 

test the results.

IMPLEMENTING HFST

In June 2012, IDOT installed a single layer of HFST at this location 

after existing pavement was shot-blasted to provide better HFST 

adhesion. Additional work included deck patching, pavement 

marking removal, joint covering, shot-blasting, and automated 

HFST application. 

Immediately after installation, IDOT measured friction values in 

the 90s and low 100s and found that they stayed approximately 

the same several months later. When tested again over a year 

later, they found that values ranged from the 80s to low 100s. 

Figure 3 displays comparative pavement friction levels taken at 

this location for:

• Existing pavement conditions prior to HFST installation, 

• Short-term friction increases provided by shot-blasting, and 

• Long-lasting friction increases after HFST installation. 

In the one year directly after HFST installation, 4 crashes occurred, 

only one involving an injury. The project cost totaled $494,000 for 

1.8 lane miles of roadway, or 0.3 miles over six lanes in the north 

and southbound directions. The treatment is expected to have 

a lifespan of 8 to 10 years, yielding an approximate benefit-cost 

ratio of 3.8.

HFST Shot-blast

Photo: FHWA

Figure 2. HFST Treatment Texture Compared to Shot-blasting Texture

Photo: FHWA

Figure 3. Pavement Friction Levels on 5-in-1 Bridge I-380, Cedar Rapids, Iowa

Existing Conditions

With HFST

Shot-Blasting Only

0 50 100

IOWA

HIGH FRICTION SURFACE TREATMENT (HFST)

By contrast, the IDOT team recognized that HFST offered several 

advantages:

• Long-lasting high friction values. Studies report that HFST skid 

values have remained upwards of 70 for several years.

• Inexpensive. HFST is labeled by FHWA’s Every Day Counts Initiative as a “low-cost” countermeasure.1

• No roadway closure. HFST can be applied one lane at a time. 

While there are alternate routes across the Cedar River, none 

of them had the extra capacity to handle the peak hour traffic 

volumes of I-380. 

• Quickly applied. The entire project could be completed in several nights and would not impact traffic during peak hours.

• Effective countermeasure for combating wet crashes. Studies 

have shown that HFST is most effective in reducing wet crashes. 

Of the 54 crashes that occurred at this location over the last 

5 years, 34 occurred during wet or icy conditions.

In spite of these benefits, IDOT’s materials and maintenance 

personnel had reservations about installing the treatment on 

a multilane interstate bridge, in a high profile location where 

multiple crashes had occurred, with high traffic and truck volumes. 

Frank Julian

FHWA Resource Center

frank.julian@dot.gov

Joseph Cheung

FHWA Office of Safety

joseph.cheung@dot.gov

FOR MORE INFORMATION

FHWA-SA-16-021

http://safety.fhwa.dot.gov

The more we considered HFST, the more 

it looked like the clear answer.

– Jerry Roche, FHWA

FEEDBACK

Shortly after installation, HFST received positive feedback from both agency personnel and the public. 

Cedar Rapids police officers expressed gratitude for the HFST installation because bridge crashes are 

now less frequent and less severe. The treatment has held up so well over the years since installation 

that IDOT’s maintenance staff now advocates for the countermeasure; they have asked to use it at 

other locations experiencing similar issues. Furthermore, the application brought public recognition 

to IDOT for solving a major safety concern and the Cedar Rapids Gazette2 praised the countermeasure 

for reducing crashes and improving safety on the bridge.

SKID NUMBER

1 Federal Highway Administration, Every Day Counts 3 Initiative, “High Friction Surface Treatments” web page. Available at: https://www.fhwa.dot.gov/everydaycounts/edctwo/2012/friction.cfm.

 

2 Erin Jordan, “Stretch of I-380 in Cedar Rapids treated with polymer sees reduction in crashes,” The Cedar Rapids Gazette, November 27, 2013. Available at: http://www.

thegazette.com/2013/11/27/stretch-of-i-380-in-cedar-rapids-treated-with-polymer-sees-reduction-in-crashes?+GazetteOnlineLocalNews+(TheGazette.com+Local+News).