U.S. Department of Transportation
Federal Highway Administration
1200 New Jersey Avenue, SE
Washington, DC 20590

Skip to content U.S. Department of Transportation/Federal Highway AdministrationU.S. Department of Transportation/Federal Highway Administration

Federal Highway Administration Research and Technology
Coordinating, Developing, and Delivering Highway Transportation Innovations

This techbrief is an archived publication and may contain dated technical, contact, and link information
Publication Number: FHWA-HRT-08-067
Date: February 2009

Traffic Calming on Main Roads Through Rural Communities

FHWA Contact: Ray Krammes,
HRDS-05, (202) 493-3312, ray.krammes@fhwa.dot.gov
Edward Sheldahl,
HSSD, (202) 366-2193, edward.sheldahl@dot.gov

PDF Version (1.09 MB)

PDF files can be viewed with the Acrobat® Reader®


Speed management is a significant challenge for most communities in the United States. This is particularly true for small, rural communities where the main roadway through the town serves a dual role. Outside the town, the roadway provides high-speed travel over long distances; within the built-up area, however, the same roadway accommodates local access, pedestrians of all ages, on-street parking, bicycles, and the many other features unique to the character of a community. This convergence of roadway purposes presents both an enforcement challenge for the community and a potential safety problem for the public.

Addressing the issue through law enforcement alone often leads to temporary compliance at a significant cost. A more permanent way to reinforce the need to reduce speed is to change the look and feel of the road by installing traffic calming treatments that communicate to drivers that the function of the roadway is changing. Traffic calming has been evaluated and used extensively within low-speed urban areas in the United States but less so in rural areas where driver expectations and traffic characteristics are different.

Traffic calming is more common in rural communities in Europe where multiple measures such as colored pavement, physical lane narrowing, signing, and landscaping are often combined.(1,2) A gateway treatment intended to evoke lower speed on the approach and entrance to the community is usually followed by a series of other measures repeated throughout the community to encourage drivers to maintain appropriate speeds. Speed reductions up to 15 mi/h from rural traffic calming have been reported in France, Denmark, and the UK, although speed reductions of 5 mi/h were more typical.(1,3) Total accidents were reduced by 50 percent and injury accidents by 25 percent or more.(3,4)

This TechBrief summarizes an evaluation of the effects on speed of low-cost, traffic-calming treatments on main rural highways passing through small, rural communities in Iowa. The full report, Appropriate Traffic Calming Techniques for Small Iowa Communities (TR-523), is available on Iowa State University's Web site at: http://www.ctre.iastate.edu/research/detail.cfm?projectID=-226410767.(5)

Study Methodology

Site Selection

Thirty rural communities (with populations less than 5,000) were identified as potential pilot-study locations through solicitation in a rural community newsletter. Site visits were conducted for each community; 18 met the initial selection criteria, which included the following:

  • Through, paved, major county or state highway.
  • No traffic calming currently in place or planned.
  • No construction, reconstruction, or significant maintenance activities planned along the route during the study period.
  • No access control.
  • No adverse geometry such as sharp horizontal curves or steep vertical curves where treatments would be placed.

Initial speed studies were conducted in the 18 communities, and 5 were selected as pilot-study locations. These five locations were found to have the most significant speeding problems, as determined by the difference between the posted speed and prevailing travel speed.

Treatment Selection

An extensive list of both traditional traffic-calming treatments used in the urban areas of the United States and treatments used specifically for major roads in small communities (identified from European and other literature) was compiled. The appropriateness of each treatment for use in built-up areas along main rural roads was determined based on the following criteria:

  • Low cost.
  • Ability to accommodate farm vehicles and large trucks.
  • Compatibility with the rural setting and driver expectations.

Treatments were selected for each study location in cooperation with local agencies.

A request for experimentation was submitted and approved by the Federal Highway Administration (FHWA) for three of the treatments that did not meet current provisions of the Manual on Uniform Traffic Control Devices.(6)

Seven different low-cost, traffic-calming treatments were implemented and evaluated in the five communities as shown in table 1. In some communities, a single traffic calming measure was installed, and in others, a combination of measures was implemented and evaluated. Speed limits ranged from 55 mi/h to 60 mi/h outside the community and from 25 mi/h to 35 mi/h inside the community where the treatments were applied.

Unless otherwise noted, treatments were placed from July through August 2006. Any treatment that included pavement markings was repainted in May 2007, just before the 12-month "after" data-collection period.

Table 1. Summary of treatments by Iowa community.
City (population) Treatment Roadway AADT (veh/day) Cross section (all are two-lane)
Union (427) Transverse pavement markings 1 with speed feedback sign D-65 (west edge of City) 830 Asphalt (22.4 ft), unpaved shoulders
Transverse pavement markings1 with speed feedback sign S-62/SH 215 (from intersection with D-65 to north city limit) 1680 Concrete (40.0 ft), curb and gutter
Lane narrowing using painted center island and edge line markings
Transverse pavement markings1 SH 215 (near south city limit) 1,000 Asphalt (22.4 ft), unpaved shoulders
Roland (1,324) Converging chevrons1 with "25 MPH" pavement legend E-18 (near east and west city limits) 2,300 Asphalt (22.6 ft), unpaved shoulders
Lane narrowing using shoulder widening & "25 MPH" pavement legend E-18 (from intersection with R-77 to east city limit) 2,300 Concrete (36.0 ft), curb and gutter
 "25 MPH" pavement legend E-18 (from intersection with R-77 to west city limit) 2,300 Asphalt (22.6 ft), unpaved shoulders
Gilbert (987) Speed table E-23 (center of community) 1,480 Asphalt (22.0 ft), no shoulders
Slater (1,306) Lane narrowing with center island using tubular markers channelizing markers R-38 (from intersection with SH 210 to south city limit) 2,060 Concrete (25.8 ft), curb and gutter
Speed feedback sign R-38 (near north city limit) 2,870 Asphalt (22.6 ft), unpaved shoulders
"SLOW" pavement legend SH 210 (west from intersection with R-38 to west city limit) 2,940 Asphalt (22.5 ft), unpaved shoulders
Dexter (689) "35 MPH" pavement legend with red background1 F-65 (near east and west city limits as well as at curve before west city limit) 1,000 Asphalt (25.4 ft), unpaved shoulders
1A request for experimentation was submitted to and approved by FHWA for this treatment.

Data Collection

Speed and volume data were collected by a roadside traffic recorder using pneumatic road tubes placed across the road. Data were collected immediately downstream of each treatment or in the case of road narrowing near the midpoint of the section. For Roland and Union where combinations of treatments were applied, data were also collected 0.5 mi upstream of the first treatment in order to determine whether speed changes observed were due to the treatments or to normal variation in speeds.

Results in this TechBrief are presented only for vehicles in the direction of travel that actually passed through the treatment. An in-depth discussion on data collected at other locations is presented in the full report.

After final locations were selected, a formal "before" speed study was conducted to establish baseline speeds and volumes. Speeds of all vehicles were collected continuously for at least 48 hours during each deployment. Data collection was planned at 1-, 3-, 6-, 9- and 12-month intervals after installation of the traffic-calming treatments. In several cases, data were not collected for a particular "after" period, mainly due to adverse winter conditions.

Most of the communities do not have any police officers and have no regular traffic enforcement, instead relying mostly on county sheriffs who drive through the community occasionally. Each community was asked to not change or request additional enforcement during the study period and to report any unusual speed enforcement or any other unusual activities. When additional enforcement or any unusual situation coincided with data collection, the data were discarded and recollected the following week. For instance, one community decorated the area around the roadway for Flag Day, and in one community roadway maintenance occurred during a data-collection period. In both cases, data were discarded and recollected. Data were only collected during nonholiday weekdays.

Measure of Effectiveness

Vehicular speed was the primary measure used to evaluate the effectiveness of each treatment. This report presents changes observed in the 85th percentile speed of all vehicles. The 85th percentile speed is the speed at or below which 85 percent of the vehicles are traveling. Each data set had at least 630 vehicle speed samples. In almost all cases, differences were statistically significant at the 95-percent confidence level.

The effects on mean speed and the percent of vehicles exceeding the speed limit by various amounts, along with statistical significance, are presented in the full report but not within this TechBrief. In most cases, only minor reductions in mean speed resulted. The changes in the percentage of vehicles exceeding the speed limit by various amount correlated with the changes in 85th percentile speeds. Overall, the treatments appeared to have a greater effect on drivers traveling at higher speeds.


The effectiveness of each traffic-calming treatment is discussed in the following sections. A brief description and photograph of each treatment is provided, along with a summary of the effects on speed.

Transverse Markings With and Without Speed Feedback Signs


The transverse markings consisted of a series of parallel bars on the inside edges of the travel lane. The spacing between bars decreased approaching the community. The series of markings are intended to create the perception that the vehicle"s speed is increasing to trigger driver awareness of the need to slow down. The transverse markings were 12 inches wide (parallel to roadway edge) by 18 inches long (figure 1). The markings were installed at the north, south, and west entrances to the city of Union. Markings were placed in advance of and terminated at the speed limit sign which established the speed within the community. The length of each series and distance between bars varied based upon each speed transition and location within the series.

Photograph of a high-speed two-lane rural roadway just outside of Union, Iowa. The pavement is marked with transverse bars on the inside edges of the travel lane entering Union. The bars are spaced closer together as drivers approach the community.

Figure 1. Experimental transverse markings at entrance to Union.

Speed feedback signs (figure 2) were also installed within Union. These signs consisted of a static "Your Speed" sign and an electronic display of the approaching vehicle speed measured by radar. These signs were installed for inbound motorists at the north and west city entrances and were placed immediately downstream of the transverse markings as shown in figure 3. Due to purchasing and installation problems, the signs did not become operational until just before the 9-month data collection period.

Photograph of an electronic speed feedback sign mounted on a post between the curb and sidewalk. The sign consists of a black-on-white panel with the legend "YOUR SPEED" mounted above a two-digit electronic sign displaying the number "47" by means of yellow lights on a black background. A solar panel is mounted at the top of the sign post. Homes can be seen on both sides of the road, as well as a few cars parked downstream on the opposite side of the road from the speed feedback sign.

Figure 2. Speed feedback sign in Union.

Map of Union, Iowa, showing the locations where traffic–calming treatments were placed and where data were collected along the two high–speed roadways acting as major roads through the community. Route D–65 is an east–west roadway, and State Route 82/215 is a north–south roadway. The transverse markings and speed feedback sign are located on the northern, southern, and western entrances in advance of the street grid for the community. An all–way STOP sign is shown in the center of town where these two roads intersect. The lane narrowing is extended from the all–way stop for four blocks to the north, which was the first intersection for southbound traffic entering Union.

Figure 3. Treatment and data collection locations in Union.


Table 2 shows the change in 85th percentile speed by location and observation period. For the south entrance (U5) where transverse markings were the only treatment installed, there was little change in prevailing speed. Similar results were found for southbound traffic entering the north side of town (U2) and eastbound traffic entering from the west (U1) prior to the installation of speed feedback signs.

Table 2. Speeds before and after transverse pavement markings with and without speed feedback sign (SFS) at the entrances to Union.
Location and analysis period Sample size (veh) Posted speed (mi/h) 85th Percentile (mi/h) Change in 85th percentile speed from before period (mi/h)
U2 SB Before 1870 30 41                
1-month 1785 30 41               0
3-month 1794 30 40             -1  
9-month (+SFS) 1737 30 35   -6            
12-month (+SFS) 1693 30 34 -7              
U5 NB Before 886 25 46                
1-month 783 25 45             -1  
3-month 943 25 45             -1  
9-month 908 25 44           -2    
12-month 871 25 45             -1  
U1 EB Before 893 25 53                
1-month 659 25 51           -2    
3-month 684 25 52             -1  
9-month (+SFS) 749 25 49       -4        
12-month (+SFS) 666 25 50         -3      

After the feedback signs were installed, speeds dropped an additional 3 mi/h to 6 mi/h at the north and west entrances during the 9- and 12-month analysis periods. Since the signs were only in place for a short period of time, it is not known if the observed speed reductions persisted over the longer term.

Lane Narrowing Using Painted Center Island and Edgeline Markings


Median and shoulder pavement markings shown in figure 4 were used to reduce lane widths for a section of S-62/SH 215 within Union. The existing two-lane roadway was 40 ft wide from curb to curb with parallel parking allowed on one side. A 10-ft-wide painted center island was used to reduce the existing lane widths from roughly 16 to 11 ft in each direction. A solid 6-inch channelizing line was painted to separate the travel lane from an 8 ft parking lane. Drivers were expected to slow down due to feeling constrained by narrower lanes.


Table 3 summarizes speed data collected midway through the narrowed section (U3), as shown in figure 3. Results are presented for both directions of traffic, as both were exposed to the lane narrowing. No other traffic-calming measures were in place at this location.

Table 3. Speeds before and after narrowing lane using painted center island and edge line markings.
Location and analysis period Sample size (veh) Posted speed (mi/h) 85th Percentile (mi/h) Change in 85th percentile speed from before period (mi/h)
U3 NB Before 2055 30 35                  
1-month 1808 30 36           +1      
3-month 1840 30 32 -3                
9-month 1807 30 36           +1      
12-month 2064 30 35         0        
U3 SB Before 2058 30 33                  
1-month 1930 30 33         0        
3-month 1911 30 37                 +4
9-month 1881 30 32     -1            
12-month 1771 30 34           +1      

No consistent changes in 85th percentile speed were observed for either direction. In some cases, vehicle speeds decreased; in other cases, vehicle speeds increased. The variability in speeds suggests that the treatment was not effective and that other factors may have influenced speeds. Speed data collected at a point upstream of the north section where vehicles were not influenced by any of the traffic-calming treatments exhibited an overall upward speed trend. This suggests the observed increases in speed were due in part to general time trends.

Even though the roadway was reduced from 16 ft to 11 ft lanes in each direction, the lanes may have still been too wide to affect driver behavior. A more drastic reduction in lane width (e.g., 9 ft lanes) or a physical barrier (e.g., raised curb) may be necessary to produce the desired effect since there are no consequences for driving over the pavement markings.

Photograph showing a main road through Union, Iowa, lined with large trees on both sides. There is a white edgeline painted on one side of the road about 8 ft from the curb. There is a painted center island in the middle of the road consisting of yellow striped markings around the outside and yellow cross-hatch markings in the center.

Figure 4. Painted center island and edgeline used to narrow lane.

Converging Chevrons with "25 MPH" Pavement Marking Legend


A series of converging chevron markings shown in figure 5 were installed on County Road E-18 on both entrances to Roland. The markings began 221 ft in advance of and terminated at the speed limit sign which established the speed within the community. The distance between chevrons gradually decreased from 25 ft to 18 ft, and the width of the markings decreased from 36 inches to 6 inches in the direction of travel, giving the perception of increasing speed. The pavement marking legend "25 MPH" was installed at the end of each chevron series to reinforce the posted speed.

Aerial photograph showing white chevrons painted on the right side of the roadway in Roland, Iowa. The chevrons point in the direction of travel and are closer together and  thinner as drivers approach the community. Just downstream of the chevron markings is the number "25" painted on the black asphalt pavement using white markings followed by "MPH," also in white markings. There is a field on one side of the road.

Figure 5. Experimental converging chevron markings followed by "25 MPH" pavement legend.


As shown in table 4, the 85th percentile speed decreased up to 4 mi/h, while 1 mi/h was more typical for the various analysis periods. Although the chevron markings were somewhat effective in reducing vehicle speeds, prevailing speeds were still 7 mi/h to 9 mi/h above the posted speed limit 12 months after implementation.


Table 4. Speeds before and after installing converging chevron markings and "25 MPH" pavement legend.
Location Analysis period Sample size (veh) Posted speed (mi/h) 85 Percentile (mi/h) Change in 85th percentile speed from before period (mi/h)
West entrance Before 4216 25 35          
   1-month 4135 25 34       -1  
3-month 3812 25 32   -3      
9-month 3958 25 35         0
12-month 3945 25 34       -1  
East entrance Before 2397 25 36          
1-month 2426 25 35       -1  
3-month 3413 25 35       -1  
9-month 2196 25 34     -2    
12-month 1778 25 32 -4        

Lane Narrowing Using Shoulder Widening with "25 MPH" Legend


A wide edgeline and cross-hatch markings, as illustrated in figure 6, were used to create a shoulder on both sides of the roadway and reduce lane widths for a section of E-18 within Roland. The existing two-lane roadway was 36 ft wide from curb to curb. The painted shoulders reduced the lane width to 10.5 ft in both directions. The narrow lane was intended to make drivers travel slower due to feeling constrained. White pavement marking legends indicating "25 MPH" were placed at regularly spaced intervals within the narrowed section to remind drivers of the speed limit.

Photograph taken in Roland, Iowa, showing two parallel white lines on both sides of a curbed roadway with cross-hatch markings inside the two lines creating a shoulder area. A "25 MPH" is painted white in the center of the travel lane. There is a sidewalk offset from the right side of the roadway, and driveways can be seen on both sides of the road.

Figure 6. Shoulder markings used to narrow travel lanes in Roland.


Data were collected at the midpoint of the narrowed section. As shown in table 5, the lane narrowing and speed limit markings were not effective in reducing vehicle speeds. There were no consistent changes in the 85th percentile speed by analysis period or direction of travel with both increases and decreases recorded. In most analysis periods, there was no change in traffic speed compared to speeds measured before the lane narrowing. No data were collected 6 months after the change due to adverse winter weather.


Table 5. Speeds before and after lane narrowing using shoulder markings combined with "25 MPH" pavement legend.
Direction of Traffic Analysis period Sample size (veh) Posted speed (mi/h) 85th Percentile (mi/h) Change in 85th percentile speed from before period (mi/h)
Outbound Before 2884 25 34            
1-month 2708 25 34       0    
3-month 2324 25 34       0    
9-month 2489 25 33   -1        
12-month 2727 25 34       0    
Inbound Before 2864 25 31            
1-month 2681 25 29 -2          
3-month 2361 25 31       0    
9-month 2562 25 31       0    
12-month 2835 25 32         +1  

Even though the eastern section of E-18 was reduced from a 36 ft cross-section to 10 ft lanes, the lanes may have still been too wide to affect driver behavior. A more drastic reduction in lane width (e.g., 9 ft lanes) or a physical barrier (e.g., raised curb) may be necessary to produce the desired effect since there are no consequences for driving on pavement markings.

Speed Table


A speed table (figures 7 and 8) was installed on County Road E-23 within the center of Gilbert. The two-lane asphalt roadway has grass shoulders, no curb, and a 25 mi/h posted speed limit. The speed table was 3 inches high and 22 ft in the direction of travel, including 6 ft ramps at both ends. The asphalt speed table was designed to be traversed at 30 mi/h to accommodate heavy trucks and farm vehicles.

An aerial photograph showing a raised speed table placed across both lanes of travel in   Gilbert, Iowa. The ramps of the table have white chevron markings pointing in the direction of travel. A park area can be seen on the north side of the road.

Figure 7. Aerial view of speed table in Gilbert.

A photograph of the speed table from the driver viewpoint. Because it is only a few inches high, it almost appears flush with the roadway. The road appears to be on a slight grade, and there is a sidewalk on the right side of road that is setback about 15 ft from the edge of pavement.

Figure 8. Driver view of speed table in Gilbert.


The speed table was very effective in reducing speeds. As shown in table 6, 85th percentile speeds were reduced at the hump location by 4 mi/h to 5 mi/h over all "after" periods to within a few miles per hour of the 25 mi/h posted speed limit. Approximately 200 ft downstream of the speed table, speeds were still 4 mi/h lower than baseline speeds and within 5 mi/h of the posted speed.

Table 6. Speeds before and after installing speed table.
Location Analysis period Sample size (veh) Posted speed (mi/h) 85th Percentile (mi/h) Change in 85th percentile speed from before period (mi/h)
200 ft downstream Before 2257 25 34            
1-month 2199 25 30   -4        
3-month 2763 25 30   -4        
9-month 3885 25 30   -4        
12-month 3886 25 30   -4        
15 ft downstream Before 3685 25 32            
1-month 3355 25 27 -5          
3-month 3413 25 28   -4        
9-month 3982 25 27 -5          
12-month 3279 25 27 -5          

Lane Narrowing with Center Island Using Tubular Markers


Tubular markers shown in figure 9 were used to create two center islands along the southern section of R-39 in Slater. At this location, the roadway is 26 ft wide from curb to curb. Center islands were formed by placing two rows of 36-inch-tall yellow tubular channelizing markers to reduce lane widths to 11 ft in each direction. The tubular markers were spaced 4 ft apart in the taper and 8 ft elsewhere. A 25 mi/h speed limit sign was placed on a mountable sign support at both ends of each island. The first island was located at the southern entrance to Slater, just after the first posted 25 mi/h speed limit sign. The second island was located approximately one block north of the first island.

Photograph showing a center island consisting of two rows of  tall, yellow, tubular markers. Double yellow centerline markings run between the two rows of markers. A 25 mi/h speed limit sign is mounted close to the pavement on a flexible post at the nose of the island. The road is straight and the roadside environment just passed the island appears very rural

Figure 9. Tubular channelizing markers used for center island to narrow lanes.

Although the treatment was designed to accommodate agricultural equipment and maintenance vehicles such as snowplows, the markers were damaged during winter operations and were removed for 6 weeks. The markers were reinstalled as soon as no more snow events were expected.


Table 7 shows the speed data collected midway between the two center islands. The data indicate the islands using tubular channelizing markers reduced vehicle speeds; 85th percentile speeds decreased by up to 3 mi/h when the tubular markers were in place and increased up to 4 mi/h when the tubular markers were removed. Similar speed changes were also observed for inbound traffic just downstream of the second island. Even with the speed drop, 85th percentile speeds were still 10 mi/h to 15 mi/h above the posted speed limit.


Table 7. Speeds before and after lane narrowing using center islands with tubular markers for traffic entering (NB) and leaving (SB) Slater.
Dir Analysis period Sample size (veh) Posted speed (mi/h) 85th Percentile (mi/h) Change in 85th percentile speed from before period (mi/h)
NB Before 2669 25 40                  
1-month 2453 25 38   -2              
6-month 2234 25 39     -1            
9-mo/markers removed 1808 25 44                 +4
9-mo/markers replaced 1549 25 37 -3                
12-month 2207 25 40         0        
SB Before 2806 25 45                  
1-month 2657 25 42 -3                
6-month 2387 25 42 -3                
9-mo/markers removed 1665 25 45         0        
9-mo/markers replaced 1402 25 42 -3                
12-month 2172 25 43   -2              

Speed Feedback Signs


A speed feedback sign pictured in figure 10 was installed on County Road R-38 for inbound traffic at the north entrance to Slater. This section of R-38 is adjacent to an elementary school, has a 25 mi/h posted speed limit, and has a rural cross-section with steep shoulders and open ditch drainage.

Photograph showing a dynamic speed feedback sign in Slater, Iowa. The sign diplays YOUR SPEED 26 in yellow lights against a black background. The number 26 is much larger than the word legend. A stop ahead sign and school crossing symbol sign can be seen in the background.

Figure 10. Speed feedback sign in Slater.

The sign display varied based upon vehicle speeds measured via radar. The sign remained blank (black) when no traffic was present or when the approaching vehicle speed was less than or equal to 25 mi/h (or greater than 75 mi/h). Between 26 mi/h and 29 mi/h, the sign displayed the text "Your Speed" along with the measure vehicle speed, as shown in figure 10. For vehicles approaching between 30 mi/h and 75 mi/h, the message "Slow Down 25" was displayed. No other traffic-calming treatments were in place at this location.

Due to sign purchasing and installation problems, the speed feedback sign was not installed at the same time as the other traffic-calming treatments in the study. Once the sign was in place, it experienced numerous electrical failures, and the analysis was limited to only one "after" period.


The speed feedback sign, when operational, was very effective. Speeds measured just downstream of the sign decreased from 37 mi/h to 30 mi/h 3 months after the sign was operational. It is not known if the 7 mi/h speed reduction can be sustained over time.

"SLOW" Pavement Legend


Pavement marking legends indicating "SLOW" (as shown in figure 11) were used at two locations along the western section of SH 210 in Slater. The first pavement legend was placed just inside the western community entrance. At this location, there was a park and a crosswalk that children used to cross to and from school and the park. The second was placed about 1,500 ft downstream of the first location.

Photograph showing the word "SLOW" painted white in the center of the travel lane in  Slater,  Iowa.  The road has a grass shoulder, and a few houses can be seen in the background that are setback from the road. A 35 mi/h speed limit sign and a bright yellow-green pedestrian warning sign can be seen just past the "SLOW" marking.

Figure 11. "SLOW" pavement legend in Slater.


The "SLOW" markings were not effective in reducing speeds. As shown in table 8, the 85th percentile speed actually increased for traffic entering Slater just downstream of the first pavement legend. There was little or no reduction in vehicle speed just downstream of the second "SLOW" marking. Data were not collected for the 12-month data collection interval because the road was resurfaced after the 9-month data collection period.

Table 8. Speeds before and after installing "SLOW" pavement legend.
Location Analysis period Sample size (veh) Posted speed (mi/h) 85th Percentile (mi/h) Change in 85th percentile speed from before period (mi/h)
First legend Before 2812 25 41              
1-month 2888 25 44             +3
6-month 2901 25 42         +1    
9-month 2570 25 42         +1    
Second legend Before 3503 25 34              
1-month 3294 25 34       0      
6-month 2886 25 32 -2            
9-month 3084 25 33   -1          

Entrance Treatment Using "35 MPH" Legend with Red Background


Speed limit markings (figure 12) modeled after European entrance treatments using colored pavement were used at the east and west community entrances to Dexter. The treatment was also placed west of the community on a curve just before a steel fabrication plant, as requested by the community. Community members were concerned about the combination of large trucks backing out of the plant and high-speed vehicles approaching the plant after negotiating a horizontal curve. A large red rectangle (9.5 ft by 12 ft) was used to frame the on-pavement "35 MPH" speed limit markings. An 8-inch edgeline was also painted along the treatments to enhance visibility.

Photograph showing a two-lane highway with red patches painted on the pavement with the number "35" painted white in the center of one red patch and the letters "MPH" painted  white in a second red patch immediately downstream. The red patches with the "35"  and "MPH" legends are painted in both directions of travel. Because the red  background markings appear freshly painted, the white "35 MPH" legends really stand out in the photograph.

Figure 12. Speed limit markings with experimental red background in Dexter.


As shown in table 9, the treatment was very effective in reducing the speed of traffic entering the community. Speeds downstream of the curve on the western edge of Dexter and at the western entrance decreased from 4 mi/h to 9 mi/h during most analysis periods. The speed reductions at the eastern entrance to Dexter were not as dramatic. This may be due in part to the prevailing speed in the baseline period at the east entrance, which was already lower than the west entrance to the community.


Table 9. Speeds before and after "35 MPH" pavement legend with red background markings.
Location Analysis period Sample size (veh) Posted speed (mi/h) 85th Percentile (mi/h) Change in 85th percentile speed from before period (mi/h)
Before curve Before 2190 35 52                    
1-month 2150 35 47         -5          
3-month 2022 35 47         -5          
9-month 4033 35 43 -9                  
12-month 2031 35 51                 -1  
West entrance Before 2,369 35 45                    
1-month 2,256 35 40         -5          
3-month 2,119 35 41           -4        
9-month 4,027 35 37   -8                
12-month 3,168 35 41           -4        
East entrance Before 4254 35 40                    
1-month 3998 35 38               -2    
3-month 2900 35 39                 -1  
9-month 4087 35 40                   0
12-month 4031 35 39                 -1  

Summary of Effectiveness

Table 10 summarizes speed impact, cost, and maintenance requirements for the various traffic-calming treatments evaluated in this study. The effectiveness of the treatments in reducing speeds varied widely.


Table 10. Summary of impacts and costs of rural traffic calming treatments.
Treatment Change in 85th percentile speed (mi/h) Cost Maintenance Application
Transverse pavement markings -2 to 0 $ Regular painting community entrance
Transverse pavement markings with speed feedback signs -7 to -3 $$$ Regular painting community entrance
Lane narrowing using painted center island and edge marking -3 to +4 $ Regular painting entrance or within community
Converging chevrons and "25 MPH" pavement markings -4 to 0 $ Regular painting community entrance
Lane narrowing using shoulder markings and "25 MPH" pavement legend -2 to 4 $ Regular painting entrance or within community
Speed table -5 to -4 $$ Regular painting within community
Lane narrowing with center island using tubular markers -3 to 0 $$$ Tubes often struck needing replacement within community
Speed feedback sign ( 3-months after only) -7 $$$ Troubleshooting electronics entrance or within community
"SLOW" pavement legend -2 to 3 $ Regular painting entrance or within community
"35 MPH" pavement legend with red background -9 to 0 $ Background faded quickly; accelerated repainting cycle entrance or within community
$ under $2,500
$$ $2,500 to $5,000
$$$ $5,000 to $12,000

The most effective treatments were the speed feedback signs, speed table, median island using tubular markers, and speed limit markings with red background. The converging chevrons and transverse pavement markings were somewhat effective with speed reductions generally less than 3 mi/h. Lane narrowing using pavement markings to create a center island, lane narrowing using shoulder markings in combination with on-pavement speed limit markings, and on-pavement "SLOW" markings were either not effective or were only marginally effective.

Lessons Learned

The following lessons were learned during the course of the study and may be helpful to small communities considering traffic calming on main rural roads:

  • Design vehicles should be considered when determining the type of traffic-calming treatment to implement. For example, farm vehicles and heavy truck traffic are common in many rural communities and must be accommodated.
  • Maintenance can be an issue with many traffic-calming treatments. For example, the tubular channelizing markers used in this study to create a center island were effective in reducing speeds, but the tubular markers were frequently struck by vehicles and required frequent maintenance. The speed feedback signs provide a different example in that, to be effective, agencies must establish the capability to troubleshoot and maintain these signs within a reasonable response time.
  • Cost effectiveness is always a factor in selecting traffic-calming treatments. While speed feedback signs were effective in all situations, their higher cost make them most appropriate for areas where it is critical that drivers slow down, such as near schools, playgrounds, or community pools.
  • Durable pavement marking materials (such as thermoplastic, tape, epoxy, or other paint alternatives) should be considered when the markings extend within wheel paths. Standard paint products wear quickly and without frequent reapplication can reduce the effectiveness of the message.
  • Community buy-in is important. In several cases, although community leadership was onboard, the community was opposed to the treatment, even when it was proven to be effective.
  • Lane narrowing using just pavement markings to create a center island or shoulder was not effective. The lane narrowing treatment that used tubular markers to create a center island was more effective, suggesting that lane narrowing is most likely to be effective when drivers are presented with a physical object that causes deflection.
  • Small communities may not be familiar with traffic calming and may need additional education.

Other Considerations

In visiting a large number of small communities to select pilot study locations, the research team observed a number of practices that could affect the successful outcome of main road traffic calming. These and other implementation issues are noted as follows:

  • Small communities often do not have a traffic engineer and appear to be addressing perceived speeding problems by lowering the speed limit, believing wrongly that this will change driver behavior. While lower travel speeds may be desirable, reducing the speed limit is not likely to have much effect.
  • Speed limits which are not consistent with the area characteristics and roadway function lead to disregard for posted speeds and create animosity toward law enforcement. The recently released USLIMITS Web-based speed zone advisor could be a useful tool in setting appropriate speed limits in rural communities.(7)
  • Speed limits in the transition zone between the rural and built-up area in small communities were often improperly set, extending well passed the edge of the community into rural agricultural areas where there was no reason for reduced speeds. In other cases, the speed reductions were abrupt without appropriate speed reduction warning signs.
  • The maximum speed reduction observed in this study was 9 mi/h. Physical measures such as roundabouts and curbed center islands may be needed to achieve the speed environment that rural communities often desire.
  • Large areas of pavement markings, such as the speed limit markings with colored background, may become slippery when wet. Communities planning to use such treatments should ensure adequate skid resistance is provided. High friction surface material should be considered.
  • Speed tables are only appropriate when the posted speed limit is 30 mi/h or less and approach speeds are less than 40 mi/h. Speed tables are not recommended for use on routes with significant (more than 5 percent) truck and bus traffic. Because emergency response times may increase, emergency service providers should be consulted before installing speed tables.
  • STOP signs should not be used for traffic calming.
  • The chevron markings, transverse markings, and red background for pavement legend evaluated in this study are not standard devices and require experimental approval in accordance with section 1A.10 of the MUTCD.


  1. Department for Transport. Traffic Calming on Major Roads, Traffic Advisory Leaflet 01/00, London, 2005.
  2. National Roads Authority. Guidelines for Traffic Calming for Towns and Villages on National Routes, Dublin, February 2005. 
  3. Clarke, A. and Dornfield, M.J. Traffic Calming, Auto-Restricted Zones and Other Traffic Management Techniques, Publication No. FHWA-PD-93-029, Federal Highway Administration, Washington, DC, January 1994.
  4. Department for Transport. Village Traffic Calming—Accident Reductions, Traffic Advisory Leaflet 11/00, London, 2005.
  5. Hallmark, S., Petersen, E., Fitzsimmons, E., Hawkins, N., Resler, J., and Welch, T. Evaluation of Gateway and Low-Cost Traffic Calming Treatments for Major Routes in Small Communities, Center for Transportation Research and Education at Iowa State University, October 2007.(http://www.ctre.iastate.edu/research/detail.cfm?projectID=-226410767)
  6. Manual on Uniform Traffic Control Devices for Streets and Highways (2003 Ed), Federal Highway Administration, November 2004.
  7. USLIMITS, (www2.uslimits.org).

Researchers—This study was performed by Center for Transportation Research and Education at Iowa State University under Cooperative Agreement Number DTFH61-06-H-00003 with the Iowa Department of Transportation. Tom Welch was the Project Director. Shauna Hallmark and Neal Hawkins were the Principal Investigators. For more information about this research, contact Ray Krammes, FHWA Project Manager, HRDS, (202) 493-3312, ray.krammes@fhwa.dot.gov or Edward Sheldahl, HSSD, (202) 366-2193, edward.sheldahl@dot.gov.

Distribution—This TechBrief is being distributed according to a standard distribution. Direct distribution is being made to the Divisions and Resource Center.

Availability—The TechBrief may be obtained from the FHWA Product Distribution Center by e-mail to report.center@fhwa.dot.gov, fax to (301) 577-1421, phone to (301) 577-0818, or online at http://www.fhwa.dot.gov/research/tfhrc/programs/safety/. The full report is available online at: http://www.ctre.iastate.edu/research/detail.cfm?projectID=-226410767.

Key Words—research, safety, Traffic calming, Speed management, Transverse markings, Chevron markings, Speed feedback signs, Lane narrowing, Tubular channelizing markers, Pavement legend, Rural roads

Notice—This document is disseminated under the sponsorship of the U.S. Department of Transportation in the interest of information exchange. The U.S. Government assumes no liability for the use of the information contained in this document. The U.S. Government does not endorse products or manufacturers. Trademarks or manufacturers' names appear in this report only because they are considered essential to the objective of the document.

Quality Assurance Statement—The Federal Highway Administration (FHWA) provides high-quality information to serve the Government, industry, and public in a manner that promotes public under-standing. Standards and policies are used to ensure and maximize the quality, objectivity, utility, and integrity of its information. FHWA periodically reviews quality issues and adjusts its programs and processes to ensure continuous quality improvement.

United States Department of Transportation - Federal Highway Administration