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RUMBLE STRIP IMPLEMENTATION GUIDE:

ADDRESSING NOISE ISSUES ON TWO-LANE ROADS

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TABLE OF CONTENTS

Introduction ..............................................................................................3

How is Rumble Strip Noise Measured? .............................................................5

Reducing Noise by Varying Placement ............................................................7

Horizontal Curves ......................................................................................................... 8

Intersections ................................................................................................................. 8

Passing Zones ............................................................................................................... 9

Reducing Noise by Varying Designs .................................................................9

Rumble Strip Dimensions.............................................................................................. 9

Offset........................................................................................................................... 10

Alternative or Experimental Designs.......................................................................... 10

Flexibility and Exceptions for Use of Rumble Strips........................................12

Outreach .........................................................................................................12

Alerting Noise Considerations for the Driver ..................................................13

Issues Affecting In-Vehicle Noise and Vibration ....................................................... 13

Research on the Effects of Varying Rumble Strip Designs 

on In-vehicle Noise and Vibration.............................................................................. 14

In-vehicle Lane Departure Warning Systems ............................................................. 14

Summary .........................................................................................................15

Case Study: Michigan Noise Study.................................................................16

Where to Learn More.......................................................................................17
PHOTO: Thinkstock

In an effort to save some of the 500,000 lives expected 

to be lost in roadway departures in the next 25 years, 

the highway community needs to move forward with 

installing rumble strips as appropriate. 
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RUMBLE STRIP IMPLEMENTATION GUIDE:

ADDRESSING NOISE ISSUES ON TWO-LANE ROADS

This guide has two primary purposes: the first is to educate noise and safety professionals about potential noise issues 

related to rumble strips, and the second is to help them prepare to respond to public complaints about that noise. The 

guide presents information from agencies that have experience with field implementation, policy development, and 

outreach. The level and importance of in-vehicle noise needed to alert the driver is also discussed briefly.

Introduction 

Longitudinal rumble strips are an effective, low-cost 

countermeasure for preventing roadway departure crashes, 

including both run-off-road and opposing-direction crashes. 

Rumble strips1,2 are milled or raised patterns near the center 

line or edge line of the roadway that provide both an audible 

warning (rumbling sound) and a physical vibration to alert 

drivers that they are crossing into opposing traffic or leaving 

the roadway. Rumble strips placed underneath center line or 

edge line striping are often referred to as “rumble stripes.”

Rumble Strip Basics. There are two main applications for 

rumble strips:3

1 FHWA, “Technical Advisory T 5040.39: Shoulder and Edge Line Rumble Strips,” Revision 1, 

November 7, 2011. Available at: http://safety.fhwa.dot.gov/roadway_dept/pavement/rumble_

strips/t504039/

2 FHWA, “Technical Advisory T5040.40: Center Line Rumble Strips,” Revision 1, November 7, 2011. 

Available at: http://safety.fhwa.dot.gov/roadway_dept/pavement/rumble_strips/t504040/

3 FHWA Office of Safety, “Rumble Strips and Stripes” web page. Available at: http://safety.fhwa.

dot.gov/roadway_dept/pavement/rumble_strips/

• Center line rumble strips or stripes (shown in Figure 1) 

can prevent head-on collisions and opposite-direction 

sideswipes, often referred to as cross-center line crashes. 

They are primarily used to warn drivers who are drifting into 

an opposing travel lane. While they are most often used 

on rural two-lane, two-way roadways, they are equally 

applicable to multilane undivided facilities. Center line 

markings are typically placed on center rumble strips, 

Photo: ConnDOT

FIGURE 1. Center Line Rumble Strips
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which have an added benefit of improving the visibility 

of the marking in wet, dark conditions. Center line rumble 

strips have been shown to reduce head-on and oppositedirection fatal and injury crashes by 45 percent on rural 

two-lane roads.4

• Edge line rumble stripes or shoulder rumble strips 

(shown in Figure 2) are primarily used to prevent run-offthe-road crashes. They warn drivers that their vehicles are 

drifting onto the roadside. While shoulder and edge line 

rumble strips perform the same function, their placement 

sets them apart. Shoulder rumble strips are common on 

freeways and other divided highways, but the decision 

to use one or the other on two-lane roads is based on a 

number of factors. The edge line rumble stripe places the 

pavement marking within the rumble strip and thereby 

improves the visibility of the marking in wet, dark conditions. 

Placing the rumble strip closer to the travel lane also alerts 

4 D. J. Torbic, J. M. Hutton, et al., NCHRP Report 641: Guidance for the Design and Application of 

Shoulder and Centerline Rumble Strips, Transportation Research Board, National Cooperative 

Highway Research Program (Washington, DC: TRB, 2009), Table 67. 

Available at http://onlinepubs.trb.org/onlinepubs/nchrp/nchrp_rpt_641.pdf

drivers that they are leaving the roadway sooner. Shoulder 

rumble strips and edge line rumble stripes have been 

shown to reduce single-vehicle, run-off-road fatal and injury 

crashes by 36 percent on rural two-lane roads. 5

Noise Effects of Rumble Strips. Challenges to rumble strip 

implementation exist in areas where the noise caused by 

vehicles hitting rumble strips is undesirable to the surrounding 

environment (e.g., nearby residents, nearby businesses, or 

in sensitive habitat areas). The sound inside the vehicle is 

important as it provides a warning to a driver that he or she may 

be leaving the roadway. However, the sound outside the vehicle 

may be disruptive to those who live near highways because 

it is intermittent and differs from other “normalized” sounds in 

those areas (e.g., highway traffic). While these rumble strips 

are designed to be traversed infrequently (e.g., when a driver 

drifts from her lane or makes a passing maneuver), citizen 

acceptance of State or local agency safety countermeasure 

strategies should be taken into consideration as it can affect 

the long-term viability of those strategies. Careful attention to 

design details can result in less nuisance hits on the rumble 

strips (i.e., vehicle tires crossing the rumble strip when a crash 

is not imminent).

5 Ibid. 

Photo: FHWA

FIGURE 2. Shoulder Rumble Strips
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How is Rumble Strip Noise Measured?

Transportation agencies use sound-level meters to assess 

and record noise levels at field locations, as shown in Figure 

3. The sound level of rumble strips can be difficult to measure 

as it occurs more intermittently than normal highway noises. 

The same basic measurements used to measure highway 

traffic noise are also used to measure rumble strip noise. The 

maximum noise level is typically the key consideration for 

rumble strips, whereas the average noise level, over a period 

of time, is the key consideration for highway noise. There is 

currently no method that adequately measures the unique 

character of rumble strip noise.

The Washington State Department of Transportation (WSDOT) 

indicates that noise issues result from both the volume and the 

sound frequency level, as low frequency noise travels farther. 6

While the concept of volume is generally understood (more 

audible sounds typically have a higher decibel level), the 

frequency isn’t generally considered when agencies take into 

account the “loudness” of sound. 

6 Interview with Dave Olsen, Matthew Enders, T.J. Nedrow, Ian Macek, Tim Sexton, Mark Russell, 

Jeff Uhlmeyer, and Steve Bennett of Washington State DOT, conducted on October 30, 2012.

Generally speaking, low-frequency waves will travel farther than 

high frequency waves because there is less energy transferred 

to the medium through which the sound passes.7 In the case of 

rumble strips, the “medium” could mean anything that resides 

in the physical space (e.g., trees, buildings, etc.) between the 

rumble strips and the noise-sensitive location (e.g., residential 

housing, schools, commercial offices). Sound levels decrease 

by 6 decibels (dB) for a point source and 3 dB for a line 

source8 every time distance between the noise source and 

the listener is doubled. For example, when a person shouts, a 

person standing 6 feet away hears the shout at 74 dB. When 

increasing the distance between the person shouting and the 

listener to 12 feet, the listener hears the noise at 68 dB. 

Figure 4 shows the variables used to assess highway noise as 

collected by sound level meters. As noise is measured near 

rumble strip sites, each variable performs an activity to assess 

the overall noise level, as described below.

7 Physics Lab Online, “Introduction to Sound,” available at: http://dev.physicslab.org/Document.

aspx?doctype=3&filename=WavesSound_IntroSound.xml

8 A point source is a single identifiable, localized source of sound. A line source is a source of 

sound that emanates from a linear (one-dimensional) geometry.

Measuring Rumble Strip Noise Inside the Vehicle

Sufficient noise and vibration levels are needed inside 

a vehicle to alert drivers they are leaving their lane. 

These critical factors help ascertain the effectiveness 

of rumble strips and are typically measured using 

equipment that is placed inside the vehicle near the 

driver seat.

Photo: Novus Environmental, Inc.

FIGURE 3. Field Noise Measurements
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• Amplifier (Bandwidth) – this measurement refers to the 

frequency of the noise. The audible range for humans is 20 

Hz to 20 kHz. 

• Frequency Weighting – this is used to account for changes 

in sensitivity of the human ear as a function of frequency.9

• Input Gain Control – this measurement indicates the 

difference in decibels between the minimum and maximum 

levels that can be accurately measured.10

• Time Averaging – this input averages the noise levels over 

a period of time.

The following noise measurement discussion comes from the 

Impact of Non-Freeway Rumble Strips Phase 1 Final Report 

performed by Wayne State University for Michigan DOT (MDOT):11

The intensity of sound is measured using either Pascals 

(Pa) or decibels (dB), which is a logarithmic measure 

of the effective sound pressure level compared to a 

standard reference level. Not all frequencies of sound 

are detected by the human ear. Consequently, sound 

measurement is typically performed using the “A”-

weighted decibel scale (denoted as dBA), which provides 

the closest approximation to the response of the human 

9 FHWA, Measurement of Highway-Related Noise, FHWA-PD-96-046 (Washington, DC: FHWA, 

1996). Available at: http://www.fhwa.dot.gov/environment/noise/measurement/measure.cfm

10 Ibid.

11 TT.K. Datta, T.J. Gates, and P.T. Savolainen, Impact of Non-Freeway Rumble Strips – Phase 1, 

Report #RC-1575, (Lansing, MI: Michigan Department of Transportation, June 2012). 

Available at http://www.michigan.gov/documents/mdot/MDOT_Research_Report_RC1575_

Report_394019_7.pdf.

ear. The FHWA maintains guidelines for the assessment 

of roadside traffic noise levels with established threshold 

levels for Leq (the average sound pressure level) and L 10 

(the sound pressure level exceeded 10 percent of the 

time) for various land-use categories.

12 13

While it is desirable to alert drivers with a loud warning inside 

their vehicles when crossing rumble strips, those who live near 

highways prefer that rumble strips produce as little noise 

outside the vehicle as possible. Table 1 compares before and 

after noise studies conducted by MDOT and relates the noise 

levels heard in everyday settings.14 This type of information can 

be used to give the public a frame of reference for potential 

noise levels. Researchers recorded all measurements at a 

50-feet lateral offset and a height of 5 feet above the 

pavement surface.

12 Electronic Code of Federal Regulations, Title 23, Chapter 2, Subchapter H, “Part 772 – 

Procedures for Abatement of Highway Traffic Noise and Construction Noise.” Web address: 

http://www.ecfr.gov/cgi-bin/text-idx?SID=63a6a40884fe0528ccf4896522f4bc4d&node=23:1.0.

1.8.44.0.1.11.31&rgn=div9. 

13 Caltrans Division of Environmental Analysis, The Effects of Highway Noise on Birds 

(Environmental BioAcoustics, LLC: 2007). Available at: http://www.dot.ca.gov/hq/env/bio/

files/caltrans_birds_10-7-2007b.pdf.

14 T.K. Datta, T.J. Gates, and P.T. Savolainen, Impact of Non-Freeway Rumble Strips – Phase 1, 

Report #RC-1575, (Lansing, MI: Michigan Department of Transportation, June 2012). 

Available at http://www.michigan.gov/documents/mdot/MDOT_Research_Report_RC1575_

Report_394019_7.pdf.

Hearing the Difference

Most research indicates humans start to hear 

differences in environmental noise levels when there is 

a 3 dB change and readily perceive 5 dB changes.13

Amplifier Frequency 

Weighting

Input Gain 

Control

Time 

Averaging

Output 

Indicator

FIGURE 4. Components of a Sound Level Meter
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Table 1: Noise Levels Before and After Rumble Strip Installation

Rumble Strip Depth, 

inches Pavement Type

Measured Noise Level Before 

(dB, ambient traffic)

Measured Noise Level After 

(dB, while driving on rumble strip) Comparison Noise Level*

0.25 Chip seal 73.3 77.5 Before: Bathtub filling 

After: Reception or lobby area

0.50 Chip seal 74.5 83.3 Before: Bathtub filling 

After: Television at 10 feet

0.38 Hot mix asphalt 69.0 76.4 Before: Garbage disposal at 2 feet 

After: Violin at 5 feet

0.56 Hot mix asphalt 69.9 84.4 Before: Garbage disposal at 2 feet 

After: City traffic (inside car)

*Acoustical Solutions, Inc., “Noise Level Chart” web page. Available at: http://www.acousticalsolutions.com/noise-level-chart

Reducing Noise by Varying Placement

The strategic consideration and placement of center line, edge 

line, and shoulder rumble strips is important as practitioners try 

to balance safety improvements with noise concerns. Standard 

agency practices may take into account noise concerns while 

recognizing there may be some unique conditions that need 

to be assessed per individual locations. Some agencies treat 

rumble strip installation differently depending on roadway 

geometry, specifically at horizontal curves and where there are 

passing zones. 

For instance, an agency could place shoulder rumble strips 

farther from the roadway or replace edge line rumble stripes 

with shoulder rumble strips to reduce the frequency of contact 

with the rumble strip or stripe. It should be recognized that 

tradeoffs related to safety, noise, or other concerns such as 

bicycle accommodation or pavement preservation may 

occur as a result of any mitigation effort. For this reason, it is 

important to evaluate the trade-offs associated with a specific 

project or location before implementing a solution. Current 

research does not yet have quantifiable information regarding 

the specifics of these trade-offs.

Several States have narrowed the focus of public noise 

complaints to locations where a section of rural highway has 

suburban characteristics. To address this situation, a single 

solution or combination of treatments may help to alleviate 

public concerns. For example:

Safety Trade-offs

Trade-offs related to safety may occur as a result of 

any rumble strip design or placement modification. 

Research has not yet determined the specific extent of 

these trade-offs.
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• MDOT allows the omission of rumble strips where the 

driveway density exceeds 30 entrances per 1⁄2 mile.15

• Missouri DOT (MoDOT) omits use of both center line and 

edge line rumble strips where the posted speed is less than 

50 mph.16

• Pennsylvania DOT (PennDOT) recommends not installing 

edge line rumble strips on the inside of moderate to sharp 

curves that are in the immediate vicinity of any residence.17

All three practices mentioned above indicate the desire to 

exclude rumble strip installation in locations with an increased 

concentration of residents. MoDOT further recommends 

omitting edge line rumble strips on major roads where noise 

may be a significant issue if there is no significant crash history 

or other risk factors.

Horizontal Curves

Placing center line rumble strips in tight horizontal curves 

requires additional consideration. Horizontal curvature can 

produce additional incidental contact (and associated 

noise) with the rumble strips due to drivers intentionally cutting 

15 Interview with Jill Morena, Tracie Leix, Deirdre Thompson, Curtis Bleech, Andy Bennett, Tim 

Croze, Marc Beyer, and Erin Chelotti of Michigan DOT and Tim Gates of Wayne State University, 

conducted on May 22 &23, 2013

16 MoDOT, Engineering Policy Guide, Section 626. Available at: http://epg.modot.org.

17 Interview with Gary Modi, Chris Speese, Lydia Peddicord, Scott Nazar, Brian Sanders, and Josh 

Freeman of PennDOT, conducted on August 27, 2013.

the curve short or inadvertently off-tracking. This is especially 

true where the operating speeds do not correlate with the 

superelevation or where the percentage of large vehicles 

is high.

Widening the pavement through the curve or designing the 

curve with a “spiral transition” can reduce the likelihood of 

vehicles crossing the center or edge line. Center line rumble 

strips can slow drivers familiar with the roadway as they travel 

through curves, particularly when the rumble strips are placed 

in conjunction with shoulder or edge line rumble strips.

Where pavement width cannot be adjusted prior to installing 

rumble strips, an option for center line rumble strips is restriping 

the pavement either to increase the travel lane width while 

reducing the shoulder width or to decrease the lane width for 

a greater median separation. 

For edge line or shoulder rumble strips, a method to mitigate 

this potential concern is to offset shoulder or edge line 

rumble strips in the specific locations where noise might 

be problematic.

Intersections

Agencies typically discontinue rumble strips in the vicinity of 

intersections and major driveways. Rumble strips are omitted 

within the intersection itself, where they would be crossed 

by turning traffic or entering vehicles. Additionally, edge line 

or shoulder rumble strips are often discontinued on each 

approach in locations with noise concerns to reduce noise 

from drivers who slow and pull to the right in advance of a 

right turn. 

WSDOT comments that “[agencies] can greatly 

control the frequency of incidental contacts by 

attention to placement details.”
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Passing Zones

Placement of rumble strips in passing zones will result in 

expected noise from passing maneuvers. With some of the 

very first installations, agencies did not place rumble strips 

in passing zones but quickly discovered that a continuous 

application was necessary to achieve the safety benefits. States 

have identified that head-on and opposite-direction-sideswipe 

crashes are as likely to occur in passing zones as they are in no 

passing zones. Most agencies mitigate noise by terminating 

rumble strips at intersections and driveways while still installing 

center line rumble strips in passing zone locations.18 

Reducing Noise by Varying Designs

Much like rumble strip placement, rumble strip design can 

have an impact on the amount of noise generated by vehicles 

as they pass over the rumble. Though placement is more likely 

to have a significant effect, WSDOT comments that, “agencies 

can slightly affect the volume of the noise generated by 

rumbles through design modification.”19

18 FHWA, “Technical Advisory T5040.40: Center Line Rumble Strips,” Revision 1, November 7, 2011. 

Available at: http://safety.fhwa.dot.gov/roadway_dept/pavement/rumble_strips/t504040/

19 Interview with Dave Olsen, Matthew Enders, T.J. Nedrow, Ian Macek, Tim Sexton, Mark Russell, 

Jeff Uhlmeyer, and Steve Bennett of Washington State DOT, conducted on October 30, 2012

Rumble Strip Dimensions

Agencies with established rumble strip implementation 

practices may have standard dimensions for construction. 

While the actual dimensions vary by agency, Figure 5 indicates 

the standard nomenclature for center line, edge line, and 

shoulder rumble strip dimensions.20,21

WSDOT has received noise complaints about their standard 

rumble strip dimensions, and, as a result, the agency has 

occasionally installed rumble strips with a shallower 3/8 

inch design. The agency is also experimenting with wider 

longitudinal spacing between rumble strips.22 Likewise, 

PennDOT recognized the need to fine-tune rumble strip designs 

and allows rumble strip depth (D) to be decreased from 1/2 

inch to 3/8 inch in passing zones.23

20 FHWA, “Technical Advisory T5040.40: Center Line Rumble Strips,” Revision 1, November 7, 2011. 

Available at: http://safety.fhwa.dot.gov/roadway_dept/pavement/rumble_strips/t504040/.

21 FHWA, “Technical Advisory T 5040.39: Shoulder and Edge Line Rumble Strips,” Revision 1, 

November 7, 2011. Available at: http://safety.fhwa.dot.gov/roadway_dept/pavement/rumble_

strips/t504039/

22 Interview with Dave Olsen, Matthew Enders, T.J. Nedrow, Ian Macek, Tim Sexton, Mark Russell, 

Jeff Uhlmeyer, and Steve Bennett of Washington State DOT, conducted on October 30, 2012

23 Interview with Gary Modi, Chris Speese, Lydia Peddicord, Scott Nazar, Brian Sanders, and Josh 

Freeman of PennDOT, conducted on August 27, 2013

Rumble Strip Gaps for Intersecting Routes 

Several agencies terminate center line and shoulder or 

edge line rumble strips in the proximity of intersections 

to mitigate noise concerns.

Varying Designs: Commercial Vehicle Use 

It may be necessary to increase rumble strip dimensions 

where large commercial vehicles are frequent road users. 

According to NCHRP Report 641, noise in the passenger 

compartment of a commercial vehicle generated by 

rumble strips has a greater effect in alerting the driver 

than the vibration.
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Offset

As agencies begin providing rumble strips on the edge 

of the travel way, they must assess the advantages and 

disadvantages associated with shoulder versus edge line 

rumble strips. WSDOT and PennDOT prefer shoulder rumble 

strips, partially to mitigate the effect of noise associated with 

rumble strip hits.24,25 While edge line rumble stripes tend to 

have more hits due to their placement closer to the traveled 

way, they have the added benefit of improved wet weather 

and nighttime visibility, greater pavement marking durability, 

and earlier warning to motorists. 

Additionally, an agency could move shoulder rumble 

strips further from the travel way to reduce the number of 

hits, but doing so may negatively impact bicyclist use of 

the shoulder. 

24 Interview with Dave Olsen, Matthew Enders, T.J. Nedrow, Ian Macek, Tim Sexton, Mark Russell, 

Jeff Uhlmeyer, and Steve Bennett of Washington State DOT, conducted on October 30, 2012.

25 Interview with Gary Modi, Chris Speese, Lydia Peddicord, Scott Nazar, Brian Sanders, and Josh 

Freeman of PennDOT, conducted on August 27, 2013.

Alternative or 

Experimental Designs

Several agencies have used 

modified rumble strip designs 

in an attempt to reduce 

noise levels. Some designs, 

like raised edge line rumble 

strips (shown in Figure 6), 

reduce external noise but do 

not provide the same level of 

internal noise and vibration 

as typical milled rumble 

strips. Currently, agencies 

are investigating rumble strip 

designs that provide sufficient 

alerting internal noise, while 

reducing external noise, as 

described below. 

FIGURE 5. Center Line, Shoulder, and Edge Line Rumble Strips and Stripes Dimension Terminology

Photo: FHWA

FIGURE 6. Raised Edge Line Rumble Strip
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Sinusoidal Rumble Strips

California Department of Transportation 

(Caltrans) is testing a sinusoidal rumble 

strip as a quieter design alternative 

(shown in Figure 7). In their March 2012 

preliminary investigation report, Caltrans 

states that “external noise from sinusoidal 

rumble strips is 3 to 7 decibels quieter 

than rectangular strips,” and concluded 

that sinusoidal rumble strips’ external 

noise is only 0.5 to 1 decibels above 

ambient noise.26 These measurements 

were taken by placing a microphone 

on one side of the two-lane road at a 

distance of approximately 25 feet from 

the roadway center line and at a height 

of approximately 4 feet above the 

road surface. 

A recent Minnesota noise study compared two 8-inch

sinusoidal designs against a conventional rumble strip of 

16-inches.27 The study included a passenger car, pickup truck, 

and tractor trailer traveling at speeds of 30 mph, 45 mph, and 

60 mph. One of the sinusoidal shapes had depth and spacing 

dimensions similar to the conventional rumble strips and the 

interior noise differential from both these rumble strips designs 

was 6 dBA or more for both the passenger car and the pickup 

truck at 45 mph. 

26 Caltrans Division of Research and Innovation, Traffic Noise Generated by Rumble Strips, (CTC 

and Associates, LLC, 2012). Available at: http://www.dot.ca.gov/research/researchreports/

preliminary_investigations/docs/rumble_strip_noise_preliminary_investigation_3-5-12.pdf

27 E. Terhaar and D. Braslau, Rumble Strip Noise Evaluation, MN/RC 2015-07, Minnesota 

Department of Transportation Research Services & Library (St. Paul, MN: MNDOT, February 

2015). Available at: http://www.dot.state.mn.us/research/TS/2015/201507.pdf.

Most interestingly, the study concluded that overall exterior 

noise produced by both of the 8-inch sinusoidal rumble strips 

was less than that produced by the 16-inch conventional 

rumble strips. Since the study did not include an 8-inch 

conventional design, it is not clear if the sinusoidal shape is 

the reason for the difference in exterior noise levels.

A number of European studies have also tested sinusoidal 

shapes, with varying results. All studies concluded that 

sinusoidal rumble strips produced marginal to no perceptible 

increase in external maximum noise level. Several Norwegian 

studies within this group indicated that the sinusoidal rumble 

strips provided adequate internal noise needed to alert an 

inattentive or drowsy driver. However, the 2013 Swedish study 

found that their sinusoidal rumble strips generated lower 

internal noise in the car and less vibration than conventional 

strips.28 These studies’ conflicting results may be due to 

differences in rumble strip design, strip dimension, and/or 

weight of vehicles used in the study.

Widely Spaced Rumble Strips

WSDOT has an ongoing rumble strip research project that 

has installed several experimental patterns. They are currently 

experimenting with wider spacing between strips and 

shallower depth (Dimensions E and D, respectively, as shown 

in Figures 5) in an attempt to reduce the roadside noise 

associated with rumble strips. The agency indicates that there 

has not been sufficient time to enable a performance study of 

these installations.29

28 A. Vadeby, A. Anund, U. Björketun, and A. Carlsson. VTI Report 790: Safe Accessibility: 

Summarised Results. 2013. Available at: http://www.vti.se/en/publications/pdf/safeaccessibility-summarised-results.pdf.

29 Interview with Dave Olsen, Matthew Enders, T.J. Nedrow, Ian Macek, Tim Sexton, Mark Russell, 

Jeff Uhlmeyer, and Steve Bennett of Washington State DOT, conducted on October 30, 2012.

Photo: Courtesy of Andreas Hegewald, BASt

FIGURE 7.

Sinusoidal Rumble Strip
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Flexibility and Exceptions for Use of 

Rumble Strips

As discussed previously, several agencies practice flexibility 

with respect to rumble strip placement and design. They may 

even choose not to install rumble strips, although general 

practice or policy recommends rumble strip installation at a 

specific location. 

WSDOT does not provide specific guidance restricting rumble 

strip installation (e.g., lane width or functional class); rather, it 

suggests assessing each road or location independently. As 

an example, the agency has learned to generally discontinue 

rumble strips prior to both intersections and narrow bridges 

due to noise concerns. 

MDOT’s Road Design Manual states that “if safety concerns 

outweigh other issues such as noise and bicycle use, nonfreeway shoulder and centerline corrugations can be 

considered for use on roadways that do not meet [other 

given] criteria.”30 This gives flexibility for agency staff to consider 

installing rumble strips on roadways with narrower shoulders 

or a low functional classification.

Both MDOT and MoDOT tend to exclude rumble strip installation 

in locations with high resident concentrations. Exclusions are 

based primarily on functional classification and posted speed 

limits. This works well for Michigan and Missouri because 

these States have very few rural roads with speed limits less 

than 55 mph.

30 Michigan DOT, Road Design Manual. Available at: http://mdotcf.state.mi.us/public/design/

englishroadmanual/

Outreach

If agencies are trying to systemically implement rumble strips 

statewide, they should consider the need for public outreach 

from both a statewide and a local perspective. Outreach 

efforts should take into account local citizens’ understanding 

and knowledge of rumble strips and may vary in different 

regions of the state. 

Practitioners should be willing to modify the design and 

placement of rumble strips on an as-needed basis (i.e., after 

assessing safety impacts) and to educate the public about 

treatment options. Some surveys have shown that informed 

citizens often consider improved safety worth the increase in 

external noise, and that residents become accustomed to the 

increased noise fairly quickly.31

An example of an often heard public comment follows, as 

does a scripted message and potential solutions:

31 FHWA, “Technical Advisory T 5040.39: Shoulder and Edge Line Rumble Strips,” Revision 1, 

November 7, 2011. Available at: http://safety.fhwa.dot.gov/roadway_dept/pavement/rumble_

strips/t504039/

Safety First...

Road user safety should be emphasized as practitioners 

respond to public concerns.
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Obstacle: “The noise level at my house will be unbearable 

when you install rumble strips!”

Message: For center line, shoulder, and edge line rumble 

strips, noise is generated only when vehicles leave their 

travel lane. Studies have also shown that when rumble 

strips end approximately 650 feet prior to residential or 

urban areas, the noise impacts are tolerable; at a distance 

of 1,640 feet, the noise generated from rumble strips is 

negligible.32

Potential Solutions: To address these complaints, some 

agencies have increased the offset of the rumble strip from 

the edge line to decrease the incidence of vehicles falsely 

traversing the rumble strips. Other transportation agencies 

have removed sections of the rumble strips that receive 

frequent nuisance hits. 33

32 G. Bahar, J. Wales, and L. Longtin-Nobel, Synthesis of Best Practices for the Implementation of 

Shoulder and Centerline Rumble Strips, Transportation Association of Canada (TAC), 2001.

33 Interview with John Miller, Joe Jones, Ashley Reinkemeyer, Michael Curtit, and John Donahue, 

Missouri DOT, conducted on June 5-6, 2013.

Alerting Noise Considerations 

for the Driver

The amount of noise needed to alert drivers is an important 

human factors issue in need of further research. 

Recommendations are available regarding the minimum 

amount of noise and vibration needed to alert drivers, 

including those who are drowsy or distracted. Existing research 

shows that a distracted driver will likely notice a 3 dBA increase 

above the ambient in-vehicle sound level, but that this change 

may be insufficient to alert a drowsy driver. A 6 dBA sound level 

increase is more likely to target all drivers sufficiently, including 

inattentive, distracted, and drowsy or fatigued drivers, with the 

necessary stimulus to correct their steering. 

NCHRP 641 recommends the following three noise level 

increases in ambient in-vehicle noise levels for effective 

rumble strips: 

• 3 dBA – minimum design value, 

• 6 dBA – desirable design value, and 

• 15 dBA – maximum design value.34

Even though these guidelines are available, common practice 

is typically based on engineering judgment. 

Issues Affecting In-Vehicle Noise and Vibration 

Many vehicle characteristics and driver behaviors or traits 

impact the amount of noise and vibration heard and 

felt inside the vehicle, which ultimately influences rumble 

strip effectiveness. 

34 NCHRP 641: Guidance for the Design and Application of Shoulder and Centerline Rumble Strips.

2009. Available at: http://onlinepubs.trb.org/onlinepubs/nchrp/nchrp_rpt_641.pdf

MoDOT has found that with new installations, noise 

complaints generally subside within a year. When 

complaints continue beyond a year, MoDOT has 

found that there is a greater likelihood of a location 

problem – where vehicles are crossing the rumble 

strips more frequently than expected. In those 

cases, they have removed the rumble strips in the 

specific roadway segment where the noise concern 

is concentrated.33 
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A vehicle’s type, size, age, and the quality of its suspension 

system all contribute to the level of interior noise and ride 

smoothness. Couple these baseline readings with the noise 

and vibrations that occur as the vehicles crosses over rumble 

strips, and there are thousands of possible noise and vibration 

level combinations that can occur when any one variable 

is changed. Some studies have concluded that larger 

commercial vehicles may be affected less by rumble strip 

noise and vibration than small passenger vehicles.

The effect of driving behavior on rumble strip effectiveness 

exhibits yet another set of variables. There are a host of 

possibilities that may affect the vehicle’s angle of departure 

when leaving the lane, such as whether a driver is drowsy, 

looking at the radio or cell phone, or impaired. This angle of 

departure plays an important role in rumble strips’ effectiveness. 

The slighter the departure angle, the more contact that 

vehicle tires have with rumble strips, leading to longer noise 

and vibration warnings. As a vehicle slowly drifts from the lane, 

the resulting rumble strip warning is maximized and gives the 

driver more notification and time to react. Rumble strips are 

not intended to be effective where lane departure angles 

are large, such as when the driver adjusts the steering wheel 

sharply to avoid an object in the road.

Lastly, vehicle speed may have a role in the in-vehicle noise 

and vibration levels. As speeds increase, the noise pitch and 

vibration frequency vary, affecting the degree to which drivers 

feel, hear and, ultimately, react to rumble strips.

Research on the Effects of Varying Rumble Strip 

Designs on In-vehicle Noise and Vibration

NCHRP 641 cites a field experiment that was conducted to use 

noise data and statistical models to determine the optimum 

dimensions for rumble strips in various conditions. Researchers 

collected sound level data on a wide range of rumble strip 

dimensions in six States. They used ordinary least squares 

linear regression models to predict the in-vehicle sound 

level differences. 

The results of the original regression model showed that 

milled rumble strips are associated with a higher sound level 

difference than rolled, while asphalt pavement surface is 

associated with a higher sound level difference than concrete. 

Additional prediction models have been developed to better 

explain the sound level difference pertaining to specific 

indicator variables. Any agency can use these prediction 

models to determine the optimum rumble strip dimensions for 

given base conditions.35

In-vehicle Lane Departure Warning Systems

Many auto manufacturers offer in-vehicle lane departure 

prevention systems or lane keeping assist systems. Both types 

of systems allow for the driver to override the automated 

warnings or corrections. The process these technologies use to 

warn drivers and prevent their vehicles from leaving their travel 

lane varies. In some systems, on- or in-vehicle cameras and 

processing systems monitor the distance between the vehicle 

and lane pavement markings. If the vehicle begins drifting 

toward the center or edge line markings, and the turn signal is 

not engaged, the prevention system may either: 

1. Give a visual, audible, or haptic warning (vibration on 

steering wheel, seat, or both); 

35 D. J. Torbic, J. M. Hutton, et al., NCHRP Report 641: Guidance for the Design and Application of 

Shoulder and Centerline Rumble Strips, Transportation Research Board, National Cooperative 

Highway Research Program (Washington, DC: TRB, 2009). Available at: http://onlinepubs.trb.

org/onlinepubs/nchrp/nchrp_rpt_641.pdf
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2. Selectively apply the brakes to help move the vehicle back 

into the lane; or 

3. Do both. 

Since these technologies work by assessing the distance 

between the vehicle and the lane markings, it stands to reason 

that the systems don’t work as well when pavement markings 

are not present, have faded, or when rain, snow, or ice impede 

the markings’ visibility.

Summary

Center line, edge line, and shoulder rumble strips effectively 

reduce roadway departure crashes and can be modified to 

address undesirable noise concerns. External noise may be 

mitigated by eliminating rumble strips along an entire noisesensitive corridor or at specific locations where nuisance 

hits are prevalent (e.g., curves, intersections, passing zones). 

Varying rumble strip dimensions or altering the spacing 

between rumble strips can also reduce exterior noise, although 

this will likely reduce the countermeasure’s effectiveness. Most 

promisingly, alternative designs (e.g., sinusoidal rumble strips) 

may maximize the interior vibration and alerting noise while 

minimizing the exterior noise. These rumble strip adaptations 

and alternatives can make this countermeasure adaptable 

to most highway systems where roadway departure crashes 

are prevalent. 

It is critical to continue installing rumble strips to prevent 

highway fatalities during the transition period as automated 

vehicle warning systems are integrated into the fleet and 

perfected to perform this alerting task without the associated 

noise external impacts.
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Case Study: Michigan Noise Study

MDOT and Wayne State University conducted a controlled 

field study in 2012 to evaluate increases in noise 

produced by rumble strips on rural two-lane highways 

in Michigan as a function of rumble strip depth and 

pavement surface type. The research team chose 12 sites 

on MDOT’s two-lane rural highways where rumble strips 

were installed in 2010. The study locations were selected 

to provide a representative balance between various 

roadway and rumble strip characteristics. Each study 

location had a posted speed limit of 55 mph (which is in 

accordance with MDOT policy).

The research team recorded rumble strip hits using 

a digital sound meter with a foam windscreen at a 

roadside location 50 feet away from the roadway center 

line at a height of 5 feet above the pavement 

surface, as recommended by the FHWA for roadside 

noise measurement. 

Pavement-Noise Results: The noise study results 

concluded that the noise produced by the test vehicle 

when in contact with the rumble strips varied based 

on the pavement surface type. Chip sealed pavement 

surfaces provided a mean peak noise measurement that 

was 1.92 dBA greater than that measured on hot mix 

asphalt pavements.

Rumble Depth-Noise Results: The milled depth of the 

rumble strip corrugation had the greatest effect on the 

noise produced when contact was made with the rumble 

strips, although the impact of depth was not linear, as 

evidenced by the sharp increase in peak noise at depths 

of 0.5 inches and above. The mean peak noise produced 

by center line rumble strips with depths of at least 0.5 

inches was 84.62 dBA compared to 77.82 dBA for center 

line rumble strips depths that were less than 0.5 inches, 

representing a 6.8 dBA difference. Center line rumble 

strips with depths of at least 0.5 inches exceeded the noise 

levels produced by tractor trailers by 1.54 dBA. Within the 

range of observed depth values (0.25 inch to 0.69 inch), 

noise levels were found to increase by an average of 

1.25 dBA per every 0.0625 inch increase in rumble 

strip depth. 

Recommendation: To prevent unnecessarily high levels of 

unwanted roadside noise, the study team recommends 

that rumble strips be milled at depths between 0.25 and 

0.50 inches.

Source: T.K. Datta, T.J. Gates, and P.T. Savolainen, Impact of Non-Freeway Rumble Strips – Phase 1, Report #RC-1575, (Lansing, MI: Michigan Department of Transportation, June 2012). Available 

at: http://www.michigan.gov/documents/mdot/MDOT_Research_Report_RC1575_Report_394019_7.pdf. 
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Where to Learn More

The following resources provide more details related to rumble strip noise, use, and design:

 NCHRP 641: Guidance for the Design and Application of Shoulder and Centerline Rumble Strips

 FHWA’s Rumble Strip Website: http://safety.fhwa.dot.gov/roadway_dept/pavement/rumble_strips/

FHWA, Office of Safety: 

Cathy Satterfield

cathy.satterfield@dot.gov 

(708) 283-3552

FHWA, Office of Environment:

Mark Ferroni

mark.ferroni@dot.gov 

(202) 366-3233
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FHWA-SA-15-033

April 2015

For more information on

Rumble Strip Implementation Guide: 

Addressing Noise Issues on Two-Lane Roads, visit:

FHWA Office of Safety

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