BACKGROUND

In rural areas, many communities are located along higher-speed roadways, but have much lower speed 

limits inside the city limits. Speed limits can often drop from as high as 55 mph down to 25 mph as the road 

feeds into the town’s center where pedestrians and bicyclists are more common. Typically, changes such as 

on-street parking or a greater number of houses or businesses give visual cues to out-of-town travelers that 

speeds will be reduced. These roadside cues are not always enough though, and additional traffic calming 

measures need to be installed to help lower vehicle speeds as drivers enter town.

CHOOSING TRAFFIC CALMING TREATMENTS AND LOCATIONS

In 2012, several communities in Iowa employed a variety of traffic calming techniques to inform motorists 

of the reduced speed limits and encourage them to slow down. Located on higher-speed roadways with 

speeds dropping by as much as 30 mph, the towns of Hazelton, Quasqueton, Jesup, Ossian, St. Charles, and 

Rowley installed five types of low-cost traffic calming treatments (shown below).1 All of these communities 

had the common goal of improving safety and managing the speeds into their towns. 

1 Experimental approval was requested from and granted by the Federal Highway Administration (FHWA), Office of Transportation Operations, Manual of Uniform Traffic Control Devices (MUTCD) team for the colored 

speed zone entrance treatment. Any agency wishing to implement a treatment that has not been included in the most recent edition of the MUTCD must request experimental approval from the FHWA.

Reducing Excessive Speeding in Rural Communities in Iowa

Case Study

SPEED MANAGEMENT

Transverse Speed Bars Colored Speed-Zone 

Entrance Temporary Island LED Flashing Speed Limits Signs Speed Feedback Signs

This pavement marking 

treatment creates a visual 

effect that encourages motorists to slow down. The 

bar placement guides motorists to direct the vehicle’s 

wheels in gaps between 

the bars, which results in 

the driver unconsciously 

slowing down.

Colored or textured 

surface treatments in the 

roadway draw motorists’ 

attention to changing 

roadway conditions.

Temporary islands made 

of raised curbing and/or 

vertical markers can be 

removed and replaced, 

as needed, and give 

drivers the sensation of 

constricted lane widths, 

thus encouraging 

deceleration. 

These speed limit signs 

have LED lights that are 

activated by motorists 

travelling above a set 

speed threshold, usually 

5 mph or greater above the 

posted speed.

The speed feedback signs 

display the motorists’ actual 

speed. 

Photo Source: Center for Transportation Research and Education (CTRE)

REDUCED

SPEED

AHEAD
http://safety.fhwa.dot.gov

The communities’ county engineers recommended the specific roadways and locations for the traffic calming treatments. With speed 

limits transitioning from 55 mph to as low as 25 mph, each of these roadways had safety and speeding-related issues. The following 

table shows the locations, speed limits, and specific treatments used in each community.

COMMUNITY ROADWAY SPEED LIMIT TRANSITION TREATMENT USED

Hazleton County Road C-57 / Hayes Street 55 mph to 25 mph Transverse Speed Bars

Quasqueton County Road W-40 55 mph to 25 mph Transverse Speed Bars

Jesup 220th Street / State Highway 939 55 mph to 35 mph Colored Speed-Zone Entrance

Ossian County Road W-42 55 mph to 25 mph Colored Speed-Zone Entrance

St. Charles

County Road R-35

State Highway 251

State Highway 251

55 mph to 25 mph

Temporary Island

Temporary Island

LED Speed Limit Sign

Rowley County Road D-47

County Road D-47 55 mph to 25 mph Speed Feedback SignLED Speed Limit Sign

The most notable 

success for these 

treatments was the 

dramatic reduction 

in excessive speeders 

(vehicles traveling 15 

mph or more over the 

speed limit).

FHWA-SA-16-079

POSITIVE RESULTS

In order to evaluate the effectiveness of these treatments in reducing speeds, the communities 

partnered with researchers to complete before and after studies. The table below summarizes the 

largest reductions for each type of traffic calming treatment considered.

Treatment Used

Reduction in 

Excessive Speeders

Average Speed 

Reduction (mph)

Colored Speed-Zone Entrance Treatment 100% 2.3

Speed Feedback Signs 79% 7.6

Temporary Island 71% 2.6

Transverse Speed Bars 54% 2.3

LED Flashing Speed Limit Signs 53% 5.9

One year after the installations, the communities saw a decrease in average speeds. However, 

the most notable success for these treatments was the dramatic reduction in excessive speeders 

(vehicles traveling 15 mph or more over the speed limit). Overall, these traffic calming measures 

have encouraged lower speeds and reduced the most aggressive speeders, thus improving safety 

for the communities.

FOR MORE INFORMATION

To view the complete research results for the speed management treatments installed in Iowa, 

access the report, Evaluation of Low Cost Traffic Calming for Rural Communities – Phase II [Updated], 

at: http://lib.dr.iastate.edu/intrans_reports/94/.

To learn more about speed management countermeasures, visit FHWA’s Speed Management Safety website.

Also, check out FHWA’s fact sheets: Speed Limit Basics and Speed Management: More than Just Speed Humps.