EXECUTIVE SUMMARY

This synthesis provides a review of shoulder rumble strip research and the rumble strips' crash reduction record.  A discussion of shoulder rumble strips as perceived by the motorist and the bicyclist is followed by the presentation of results of three nationwide surveys conducted in 2000 of State DOTs regarding shoulder rumble strips.  A comparison of policies, practices and alternative designs is utilized as the basis for illustrating the components of a bicycle tolerable shoulder rumble strip policy.  Finally, the need for future research is assessed.

TABLE OF CONTENTS

1.0  INTRODUCTION

2.0  LITERATURE REVIEW

2.1  Previous Research
2.2  Ongoing and Future SRS Research

3.0  SRS DESIGNS.

3.1  Milled SRS.
3.2  Rolled SRS.
3.3  Dimensions and Offset.
3.4  Safety Record.

4.0  EFFECT ON DIFFERENT ROADWAY USERS.

4.1  The Driver's Experience.

4.1.1  The Driver and Motor Vehicle Auditory Stimulus.
4.1.2  The Driver and Motor Vehicle Vibrational Stimulus.

4.2  The Bicyclist's Experience.

4.2.1  The Bicyclist and Bicycle Auditory and Vibrational Stimulus.
4.2.2  Other Bicyclist's Concerns.

4.3  Motorcycles.
4.4  Other Vehicles.

5.0  SUMMARY OF SHOULDER WIDTHS AND POTENTIAL SRS PROBLEMS.

6.0  SURVEY OF STATES' POLICIES AND PRACTICES.

6.1  Minnesota DOT Survey (February 2000)
6.2  FHWA Survey (Spring 2000)
6.3  FHWA Survey (September 2000)

7.0  SRS PRACTICES.

7.1  Skip Pattern.
7.2  Transverse Width of SRS.
7.3  Depth of SRS.
7.4  SRS Placement.

8.0  SRS POLICY.

8.1  Policy Classification.
8.2  SRS Installation Warrants.
8.3  Recommended Inclusions into any SRS Policy.

9.0  PROPOSED RESEARCH.

9.1  High Priority Research.
9.2  Medium Priority Research.
9.3  Low Priority Research.

Appendix A.

Decibel Levels.

Appendix B.

Mn/DOT Survey.
FHWA Spring Survey.
FHWA September 2000 Survey.

Appendix C.

Arizona Rumble Strip Policy.

Appendix D.

Minnesota Rumble Strip Policy.
Cited References.

CITED REFERENCES

BIBLIOGRAPHY.

1.0  INTRODUCTION

The first shoulder rumble strips (SRS) appeared on New Jersey's Garden State Parkway in 1955 when 25 miles of singing shoulders were installed in Middlesex and Monmouth counties.  The singing shoulder was a strip of corrugated concrete that produced a sound when driven upon.  These early SRS were later resurfaced into smooth shoulders in 1965.  A more detailed history of SRS usage is provided by Ligon et al. (1) in Effects of Shoulder Textured Treatments on Safety.

From the 1960s on, various States have utilized SRS in a variety of forms. Due to the growing record of documented studies on safety effectiveness of SRS, an increase in installation on many high volume roads has occurred in the past ten years. The popularity of SRS has recently led to their installation on many two-lane rural roadways.

The League of American Bicyclists (LAB) alerted Congressman James L. Oberstar of safety concerns SRS present bicyclists.  In an effort to ease bicyclists' concerns regarding SRS, the Federal Highway Administration (FHWA) met with the LAB and Congressman Oberstar. A product of this meeting was a decision for FHWA to produce a report on current SRS policies, designs, and usage. While it is documented that SRS are an effective means of preventing certain types of crashes, FHWA is concerned about the challenges that SRS present to some roadway users. Due to this concern, FHWA assigned Science Applications International Corporation (SAIC) to perform a synthesis regarding SRS practices and policies.

The following synthesis:

• Identifies current and near-term SRS research,
  
  
• Reports on the current status of State Department of Transportation (DOT) practices and policies, and
  
  
• Highlights areas where further SRS research is required.
  

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2.0  LITERATURE REVIEW

2.1  Previous Research

Various research and evaluation studies have been performed on SRS since their conception in the mid-1950s.  This literature review focuses on work performed since 1984.

Higgins and Barbel (2) performed research in Illinois in 1984 regarding vibration and noise produced by SRS.  While it was determined that outside noise did not significantly vary with different types and configurations of SRS, it was determined that SRS produced a low frequency noise that increased the ambient decibel (dB) level an additional 7 dB over noise levels produced by traffic on normal pavement.  In general, most measured frequencies were between 50 and 160 Hertz (Hz).

Ligon et al. (1) performed chi-squared analyses on before-and-after accident data for freeways and expressways with SRS in 1985.  The research revealed a 19.8 percent decrease in accidents at test sites with SRS as compared to a 9.3 percent increase in accidents at control sites.  The researchers concluded that their analyses involving accident rates did not show significant differences when looking at the following variables on roadways with textured treatment: high ADT versus low ADT sites; day versus night reduction in accidents; wide versus narrow shoulder textured treatments; or spaced versus continuous shoulder textured treatments.  The authors recommend the placement of textured treatments as close to the edgeline as possible on Interstate shoulder segments as they are resurfaced.

In 1993 Cheng et al. (3) performed a before and after analysis of 1990-1992 crash data on Utah roadways.  It was determined that freeways without SRS experienced a higher rate of run-off-road (ROR) crashes (33.4 percent) compared to those with SRS (26.9 percent).  Additionally, highway segments with asphalt SRS that were continuous and located near the travel lane experienced lower accident rates than highway segments with concrete SRS that were discontinuous (skip pattern) and offset from travel lane.  Also included in the report was an informal survey of 126 cyclists regarding SRS placement, in which 46 percent preferred SRS placement near the edgeline and 35 percent preferred SRS placement near the edge of shoulder.

In 1994 Wood (4) evaluated data from the first five Sonic Nap Alert Pattern (SNAP) projects that were installed on the Pennsylvania Turnpike.  The evaluation showed a 70 percent reduction in drift-off-road (DOR) crashes and resulted in milled SRS being installed over the entire length of the Turnpike.

Khan and Bacchus (5) presented economic and safety benefits to bicyclists derived from highway shoulder use in a 1995 study.  The authors commented that it is relevant to note that the addition of SRS improve the benefit-cost ratios considerably because their benefits are much higher than their costs.

In a follow-up study to the 1994 Wood study, Hickey (6) reviewed the initial results in 1997 and added traffic exposure in order to compare accident rates per vehicle-distance-traveled.  Additionally, adjustments were made to account for a decline in all accidents during the study years.  The study revised the initially reported 70 percent crash reduction to a 65 percent reduction.

Data collected by the New York State Department of Transportation (NYSDOT) and the New York State Thruway Authority (NYSTA) was utilized by Perrillo (7) in 1998 to perform a before and after analysis.  The results of the analysis for both agencies revealed at least a 65 percent reduction in ROR crashes on rural Interstates and parkways due to milled SRS.

In a 1999 study, Griffith (8) extracted data from California and Illinois and estimated the safety effects of continuous rolled SRS on freeways.  To perform this study, treatment and downstream freeway sections were initially analyzed for all fatigued/drowsy crashes.  It was not possible to identify all fatigued/drowsy crashes in this dataset, therefore, an alternative analysis was performed using alcohol/drug-impaired drivers as a substitute for fatigued drivers.  The results from this analysis estimated that continuous SRS reduced single-vehicle ROR crashes on average by 18.3 percent on all freeways (with no regard to urban/rural classification) and 21.1 percent on rural freeways.

Moeur (9) tested 28 bicyclists (5 basic, 17 skilled and 6 experienced) in a 2000 Arizona field study by having them ride over various skipped SRS sections to determine acceptable skip patterns.  It was determined that 3.7 m (12 ft) skips in ground-in SRS pattern would acceptably permit bicyclists to cross at high speeds (speeds were assumed to be between 37-45 kph, (23 - 28 mph)).  Either 12.2 or 18.3 m (40 or 60 ft) cycles for the skip pattern were determined acceptable.

The objective of the Pennsylvania Transportation Institute project performed in 2000 by Elefteriadou et al. (10) was to develop new SRS configurations that decrease the level of vibration experienced by bicyclists while providing an adequate amount of stimulus to alert inattentive or drowsy drivers.  Six configurations were tested by 25 intermediate and advanced bicyclists.  The researchers recommended the adoption of two new bicycle-tolerable rumble patterns, one for non-freeway facilities operating near 88 kph (55 mph) and the other for those operating at 72 kph (45 mph).

Chen (11) performed an analysis of milled, rolled and corrugated SRS in 1994 at 112 differently location on two Interstates in Virginia.  A portion of the report is devoted an a theoretical analysis of tire drop, which is used to help determine SRS effectiveness.  The analysis showed that tire drop can be up to 50 times greater for milled SRS than rolled SRS at a critical speed of 105 kph (65 mph).  Chen concluded that milled SRS were more effective than rolled SRS since they were found to produce 12.5 times more vibrational stimulus and 3.35 times more auditory stimulus.  Finally, it was noted in a survey conducted by Chen that an increasing number of jurisdictions believe that rolled rumble strips have very little effect on trucks.

In 2001, the California Department of Transportation (Caltrans) (12) performed a study of various SRS designs, as well as five prototypes of incised or pressed rumble strip configurations.  This study was based on the work done by Elefteriadou et al. (10).  Six test vehicles, ranging from a compact automobile to large commercial vehicles were used to collect auditory and vibrational data while traversing the SRS.  Two test drivers were asked to subjectively rate characteristic of the various test patterns, based on the driver's perspective.  Finally, 55 bicyclists of various skill levels and ages volunteered to evaluate the SRS designs.  The recommendation of the study was to replace the existing rolled SRS design with a milled SRS design that is 300 mm (1 ft) in transverse width and 8 ± 1.5 mm (5/16 ± 1/16 in) in depth on shoulders that are at least 1.5 m (5 ft) wide.  For shoulders less than this width, the installation of raised/inverted profile thermoplastic was recommended.

Outcalt (13) led a research effort in 2001 that compared various styles of SRS in Colorado.  The study's recommendations were based upon the input of 29 bicyclists as well as vibrational and auditory data collected in four different types of vehicles.  While data was collected on milled and rolled asphalt SRS and milled concrete SRS, no recommendations were made concerning concrete SRS.  Of the ten styles tested, those that provided the most noticeable vibrational and auditory stimuli to the vehicle were rated worst by bicyclists.  The milled SRS with a depth of 9.5 ±3 mm (3/8 ± 1.8 in) on 305 mm (12 in) centers in a skip pattern of 14.6 m (48 ft) of SRS followed by 3.7 m (12 ft) of gap was recommended.

2.2  Ongoing and Future SRS Research

Table 1 presents on-going and proposed rumble strip research efforts, as of March , 2001.

Table 1.  On-Going and Proposed SRS Research Efforts.

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3.0  SRS DESIGNS

Currently, SRS of various types, patterns, and designs are used in almost every State.  There are four types of SRS designs: milled, rolled, formed, and raised; the two that are most common are milled and rolled.  Since these are the predominate types installed, the remainder of this synthesis will deal with these.  The differences between these types of SRS are installation procedure and shape, which affects the amount of noise and vibration produced.

3.1  Milled SRS

Milled SRS can be placed on either new or existing asphalt or Portland cement concrete (PCC).  A milled SRS is made with a machine that cuts a smooth groove in the roadway's shoulder.  A SRS pattern results when SRS are repeated at regular intervals, as shown in Figure 1.  This type of SRS modifies the pavement surface and provides for a vehicle's tires to drop, which creates high levels of vibrational and auditory stimuli.

Figure 1.  Milled SRS.

3.2  Rolled SRS

Rolled SRS are pressed into freshly laid asphalt pavement, as shown in Figure 2.  Depressions in the hot pavement are made with a roller that has steel pipes welded to a drum.  Rolled SRS are generally rounded or V-shaped and produce lower levels of auditory and vibrational stimuli than milled SRS.

Figure 2.  Rolled SRS.

3.3  Dimensions and Offset

The SRS's transverse and longitudinal widths, spacing and depth can be modified to vary the amount of vibration and auditory stimuli produced.  However, Isackson (14) noted in a nationwide survey conducted by the Minnesota DOT (Mn/DOT) that the actual dimension of the SRS varies slightly from State to State.  While specific dimensions will be discussed in a following section, Table 2 and Figures 3 and 4 show the layout of a typical SRS:

Table 2.  Standard Dimensions of Milled and Rolled SRS.

Figure 3.  Standard Measurements of SRS.

Figure 4.  SRS Tire Drop and Depth Illustration.

Isackson also noted that the offset of the SRS (with respect to the edgeline) varies greatly from State to State.  While the vast majority of States offset the SRS between 150 600 mm (5.9 - 23.6 in) from the edgeline, it is possible to find States that place the strip directly next to or partially under the edgeline or install them as far away as 900 mm (35.4 in).  Assuming a SRS with a traverse width of 305 mm (12 in) on a 1830 mm (6 ft) shoulder, the recovery area can range from 1525 - 610 mm (60 - 24 in).

3.4  Safety Record

Even though alternative SRS designs have been used, evaluation studies have demonstrated that SRS are effective in preventing ROR crashes.  Table 3, taken from a report by FHWA's Wyoming Division Office posted on FHWA's rumble strip website entitled Shoulder Rumble Strips B Effectiveness and Current Practice (15), presents additional evaluations conducted since 1985.  The success of SRS appears to have led several States to require the incorporation of SRS on 3R projects (reconstruction, rehabilitation or resurfacing) on limited access roadways.

Table 3.  SRS Studies and Associated Crash Reductions.

note: The FHWA study included Arizona, California, Mississippi, Nevada and North Carolina.
source: Shoulder Rumble Strips B Effectiveness and Current Practice (15)

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4.0  EFFECT ON DIFFERENT ROADWAY USERS

Simple auditory and vibrational warnings are known to be an effective means of providing an urgent message to an operator.  Auditory stimulus have been used for many years by human factors engineers and motor vehicle design engineers as a warning to alert a driver of an important situation.  More recently, vibrational stimulus has been used in motor vehicles to provide a warning.

4.1  The Driver's Experience

The driver that traverses a SRS typically is doing so as their vehicle unintentionally veers from the travel lane.  This driver may be inattentive, fatigued, or under the influence of drugs or alcohol.  In any case, the driver experiences both an auditory and vibrational warning when the vehicle's tires roll over the SRS.

Ideally, when a driver encounters a SRS the desired reaction is to have them regain their attention and steer back onto the travel lane.  However, depending on the level of the driver's inattention, this desired reaction may not happen.  For a semi-alert driver (e.g., one changing the radio station) it is believed that the driver will simply refocus their attention and steer the vehicle back onto the travel lane.  For a driver that is asleep the possibility exists that the reaction to the SRS could be greatly exaggerated, to the extent of sharply turning the steering wheel and swerving into the adjacent lane or even off the roadway.  Unfortunately, the frequency of this hypothesized scenario is unknown; no research has been identified to determine what actions a driver will take when suddenly awakened while driving.  What is known is that to determine the amount of stimulus required to alert an inattentive driver is compounded by the fact that different types of vehicles travel the roadway.

Table 4 presents common transportation sounds and their associated decibel levels.  As can be seen, the sound level of city traffic measured from inside a car is 85 dB and is similar to the sound level measurement of heavy traffic.  Perrillo (7) reported that the sound inside an operating passenger vehicle is approximately 60 dB.  The sound level of a car traveling on a highway could not be found for this synthesis, but it can be assumed to be comparable to the sound level of freeway traffic, 70 dB (assuming no radio or conversation occurring in the car).  Given these decibel levels, the auditory warning generated by the SRS must be able to be heard inside the vehicle.  A more detailed discussion of decibel levels can be found in Appendix A.

Table 4.  Common Transportation Sounds and Their Associated Decibel Level

source: League for the Hard of Hearing (16)

The auditory warning created as a vehicle passes over a SRS sounds much like a low rumble to the driver.  Typically, the sound produced inside the vehicle by the SRS is not much louder that the ambient level already inside the vehicle, and at times may be even less.  Therefore, it is important to determine the level of auditory stimulus required to be heard inside the vehicle.

One of the most obvious ways to measure the auditory stimulus produced by a SRS is to measure its loudness.  Various researchers have made this measurement both inside and outside of the vehicle.  Higgins and Barbel (2) reported that when a vehicle traveled over SRS, an increase in the order of 7 dB over regular road noise was recorded at locations 15 m (49.2 ft) from the SRS.  Additionally, it was determined that peak noise levels averaged at 87 dB in a cab of a tractor-trailer while the tests were performed.

In 1988 various SNAP patterns were tested by the Pennsylvania DOT and reported by Wood (4) in 1994.  Auditory measurements were taken inside test vehicles as they passed over five different milled rumble strips designs at different speeds.  The data revealed that as speed increased, associated decibel level increased.  The test vehicles used were a sedan passenger car and a dump truck.

In Chen's (11) research, which compared various types of SRS, one characteristic of SRS that was measured was the loudness of the auditory stimulus.  At speeds of 105 kph (65 mph), milled SRS were measured between 85 86 dB and rolled SRS were measured at 74 79 dB.  The measurements were taken 61 m (200 ft) from the vehicle.  It was further noted that a 3 dB difference between the milled and rolled SRS was noticeable to drivers.

More recently, Elefteriadoiu et al. (10) reported sound levels inside the passenger compartment of a minivan when traversing six different milled SRS at speeds of 72 and 88 kph (45 and 55 mph).  While at the slower speed, the sound levels increased from an ambient level of 68 dB to approximately 79 dB.  Likewise, at the higher speeds, the sound levels increased from an ambient level of 65 dB to approximately 81 dB.

The Caltrans study (12) recorded sound levels inside the cabin of passenger vehicles and heavy trucks with the vehicle's fan and radio off and all of the windows closed.  Testing revealed an increase in average auditory stimulus ranging from 11.0 - 19.9 dB for passenger cars at test speeds of 80 and 100 kph (50 and 62.5 mph).  Heavy trucks produced a lower amount of auditory stimulus when measured inside the cabin, ranging from an average of 1.8 dB - 4.7 dB.  However, due to a space constraint at the testing facility, heavy trucks were only tested at speeds of 80 kph (50 mph).

Outcalt (13) compared sound levels for vehicles taveling on SRS against those traveling on smooth pavement at speeds of 88 and 105 kph (55 and 65 mph).  The author used a generally accepted 6 dB increase in cabin sound level as a clearly noticeable sound level increase to alert a motorist.  Overall, sound levels were louder for SRS with larger longitudinal widths.

Table 5 summarizes the five described studies, associated decibel levels produced, and the location of the measurement.

Table 5.  Decibel Levels Produced by Milled and Rolled SRS.

Research performed by Harwood (17) in 1993 determined that by modifying the repeat pattern of the SRS pattern, the noise level produced could be changed.  Of the repeat patterns tested, 3048 mm (10 ft) patterns produced the lowest noise levels.  When the repeat pattern varied between 1524 mm (5 ft) and 3048 mm (10 ft), the noise levels produced decreased linearly with vehicle speed.  Repeat patterns ranging from 305 915 mm (1 3 ft) produced noise levels that varied erratically and were considered undesirable.

Another method to measure the auditory stimulus produced by SRS is to determine the frequency produced.  The Higgins and Barbel (2) study was the only research identified that measured the frequency of the sound produced by SRS.  While the SRS tested produced frequencies on the low end of the scale (80 Hz 315 Hz), some high level frequencies in the area of 1000 Hz were measured.  While it was shown that speed has some effect on frequency, no research has been identified regarding the effect of SRS dimensions on frequency.

The vibrations produced when a vehicle passes over SRS typically begin at one of the front tires.  Vertical and lateral accelerations of the tire are transferred though the vehicle to its steering wheel, seats, and floor in the form of vibrations.  These vibrations must be gentle enough so that the driver of a compact car does not lose control but strong enough that the driver of a sport utility vehicle (SUV) or large truck is able to feel them.  As assortment of vehicle types may encounter SRS, therefore, most SRS appear to be designed with large trucks as the design vehicle.

Recent advances in technology have made vibrational measurements much easier to obtain. Chen (11) developed a theoretical analysis of the tire drop to establish a measurement of effectiveness of the SRS.  It was hypothesized that to generate adequate auditory and vibrational stimuli, the longitudinal width of the strip should be large enough for the tire to drop into the grove.  Based on standard SRS dimensions used in Virginia, Chen concluded that milled SRS perform better than rolled SRS since the tires only drop to the bottom of milled SRS.  Field tests verified that milled SRS produced greater vibrational and auditory stimuli than rolled SRS.  However, as noted by Elefteriadoiu et al. (10), Chen's theoretical analysis was based on solid wheels, not elastic motor vehicle tires.

The study by Elefteriadoiu et al. (10) compared five proposed bicycle tolerable SRS designs to Pennsylvania's existing pattern.  In this study, a minivan was instrumented to measure vertical acceleration and pitch angular acceleration.  When the accelerations of the five proposed designs were compared to accelerations of the existing design, it was determined that the difference was insignificant.  No further in-vehicle vibration tests were performed.  The depth of the five proposed designs ranged from 6.3 13 mm (0.25 0.5 in) while the Pennsylvania existing pattern had a depth of 13 mm (0.5 in).

Four accelerometers were mounted to the steering wheel of test vehicles in the Caltrans study (12) to test for vibrational stimulus.  A general trend was found in the vibrational stimulus produced, as the depth of the SRS increased, so did the amount of vibrational stimulus.  An interesting observation regarding the heavy vehicles at speeds of 80 kph (50 mph) occurred; when the existing rolled SRS was compared to the proposed milled designs, the average vibrational stimulus of the rolled SRS was slightly greater.

Outcalt (13) had a minivan equipped with two accelerometers to measure vibration.  One was installed on the floor just behind the driver and the other was installed on the steering wheel.  Vibrational measurements were taken at 88 and 105 kph (55 and 65 mph) on both SRS sections and smooth pavement.  Results showed that  SRS with larger longitudinal widths produced greater vehicle vibrations.

4.2  The Bicyclist's Experience

Bicyclists nationwide have reported safety problems associated with rumble strips.  A combination of this concern and laws enacted by some States have led most bicyclists to ride as far to the right of the travel lane as practicable or on the shoulder.

When traveling on the shoulder, debris covering the shoulder or a narrowing of the shoulder due to an overpass may force the bicyclist onto the travel lane.  If the shoulder has SRS placed near the edgeline, then the bicyclist must travel over the SRS to get off of the shoulder.  The accepted useable shoulder width required for a bicycle to travel is 1220 mm (4 ft), as stated by the American Association of State Highway and Transportation Officials (AASHTO) (18).  In instances when a guardrail or curb may infringe on this width, the generally accepted practice is to increase this with to 1525 m (5 ft), so the bicyclist may ride further away from the guardrail and still have an effective width of 1220 mm (4 ft).

When considering the combined weight of a bicycle and bicyclist, the sound a bicycle makes when traveling over a SRS is not loud enough to cause much of a problem.  However, the vibration that is produced is of a great concern to a bicyclist.

It has been proposed by Chen (11) that the deeper the vertical drop (depth) of the SRS, the greater the vibrational stimulus provided to the errant driver.  It was shown by Moeur (9) that the larger the depth of the SRS the more difficult for the bicyclists to retain control of their bicycle while crossing the strips, even at low speeds.  However, Gårder (19) concluded from a test of milled and rolled rumble strips 12 mm (1/2 in.) deep, which he and 20 others traversed on a bicycle, that there is no danger if a bicyclist mistakenly crossed a rumble strip.

In the study by Elefteriadoiu et al. (10), the five proposed bicycle tolerable SRS designs were evaluated by 25 intermediate and advanced bicyclists.  Once again, vertical acceleration and pitch angular acceleration were measured, as well as having each participant subjectively rate the proposed designs on comfort and control.  Low, intermediate, and high approach speed, as well as three approach angles (0°, 10°, and 45°) were tested.  When the acceleration measurements were examined and the subjects' subjective rankings were tabulated, it was determined that the most tolerable design for bicyclists had a depth of 6.3 mm (0.25 in) and caused the least auditory and vibrational stimulus for motor vehicles.

Fifty-five bicyclists in the Caltrans study (12) were asked to subjectively rate the various test strips on comfort and control level.  Participants were allowed to ride over the test strips as many times as necessary, both alone and in groups.  Milled SRS that were not as deep were favored by the bicyclists when compared to deeper milled SRS.  An additional analysis based upon major demographic variables found three bicyclist variables to be significant: riding in inclement weather, age, and whether a bicyclist has ridden on SRS.

Of the 29 bicyclists surveyed in the Outcalt (13) study, 27 used bicyclists with narrow, high-pressure tires.  Bicyclists rated each SRS design for control and comfort.  Overall, the survey concluded that while bicyclists can navigate 9.5 mm (3/8 in) deep SRS fairly easily, when grooves are 13 mm (1/2 in) deep or greater, bicyclists may experience control problems. 

Many bicyclist believe that SRS near the edgeline force bicycles further from the sweeping action of passing vehicles that push debris from the travel lane.  Thus, the bicyclist is forced to ride in heavier debris.  Harwood (17), Moeur (9), and Gårder (19) have commented that shoulders may at times be covered with debris and have acknowledged a vehicle's sweeping action; however, no research has been identified to document the width of the sweeping action based upon vehicular speed or volume. 

At the current time there are two ways to deal with shoulder debris.  The first is to have maintenance crews routinely sweep the shoulders.  The second is to place a skip (or gap) in the SRS pattern to allow bicyclists to cross from the shoulder to the travel lane when encountering debris, but this does not ensure that debris will not be in the skip pattern.

In addition to shoulder debris, other dislikes of bicyclists with respect to SRS are listed below

• SRS are appearing on more and more roads that are frequented by bicyclists,
  
  
• SRS often appear without warning,
  
  
• SRS that are placed close to an intersection,
  
  
• Different States have different standards and designs, and
  
  
• Weaving SRS (poorly installed SRS that are supposed to be in a straight line) are difficult for bicyclists to ride near.

4.3  Motorcycles

Caltrans has performed a motorcycle SRS evaluation of various SRS designs.  In its study, participants rode over a series of various SRS at either 88 or 105 kph (55 or 65 mph) or another speed they were comfortable with and then asked to rate their comfort and control for each of the SRS traversed.  It has also been reported Kansas and Massachusetts have tested motorcycles traversing rumble strips.  While the composition of the Kansas test group was unknown, the Massachusetts test group was comprised of the police motorcycle squad.  Both test groups reported noticing the rumble strips, however, they did not feel out of control.

4.4  Other Vehicles

Little information was identified regarding SRS and maintenance vehicles, such as those used for snowplows operation.  It was commented in telephone conversations with some State DOTs that when travel lanes are first plowed, snowplow operators may use SRS to help them maintain their course.  However, when plowing the shoulder, drivers have commented negatively regarding the vibrations caused by the SRS.

It has been suggested that maintenance trucks equipped with snowplows, wide loads tractor-trailers and other vehicles that typically ride over SRS may want to have dampening devices installed on the vehicle to lessen the effect of the SRS.  However, at this time no dampening device in known to exist.

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1. Ligon, Claude, et al.  Effects of Shoulder Textured Treatments on Safety.  Federal Highway Administration, FHWA/RD-85/027, 1985.
   
   
2. Higgins, J. S. and W. Barbel.  Rumble Strip Noise.  Transportation Research Record.  No. 983, 1984, 27-36.
   
   
3. Cheng, Eric, et al.  Application and Evaluation of Rumble Strips on Highways.  Utah Department of Transportation.  Online Posting.  http://safety.fhwa.dot.gov/rumblestrips/resources/chengite.htm.  August 2000.
   
   
4. Wood, Neal E.  Shoulder Rumble Strips: A Method to Alert Drifting Drivers.  Pennsylvania Turnpike Commission.  January 1994.  Online Posting.  http://safety.fhwa.dot.gov/rumblestrips/resources/snap4pub.htm.  August 2000.
   
   
5. Khan, A. and A. Bacchus.  Economic Feasibility and Related Issues of Highway Shoulder Rumble Strips.  Transportation Research Record.  No. 1498, 1995, 92-101.
   
   
6. Hickey Jr., John.  Shoulder Rumble Strips Effectiveness; Drift-Off-Road Accident Reductions on the Pennsylvania Turnpike.  Transportation Research Record.  No. 1573, 1997, 105-109.
   
   
7. Perrillo, Kerry.  The Effectiveness and Use of Continuous Rumble Strips.  August 1998.  Online Posting.  http://safety.fhwa.dot.gov/rumblestrips/resources.rumblekp.htm.  August 2000.
   
   
8. Griffith, Michael.  Safety Evaluation of Continuous Shoulder Rumble Strips Installed on Freeways.  Transportation Research Record.  No. 1665, 1999, 28-34.
   
   
9. Moeur, Richard.  Analysis of Gap Patterns in Longitudinal Rumble Strips to Accommodate Bicycle Travel.  Transportation Research Record.  No. 1705, 2000, 93-98.
   
   
10. Elefteriadoiu, L. et al.  Bicycle Tolerable Shoulder Rumble Strips.  Pennsylvania Department of Transportation, 2000.
    
    
11. Chen.  A Study of Effectiveness of Various Shoulder Rumble Strips on Highway Safety.  Virginia Department of Transportation, 1994.
    
    
12. California Department of Transportation.  Evaluation of Milled-In Rumble Strips, Rolled-In Rumble Strips and Proprietary Applications.  California State.  Draft Report.  February 2001.
    
    
13. Outcalt, William.  Bicycle-Friendly Rumble Strips.  Report No. CDOT-DTD-R-2001-4.  Colorado Department of Transportation, 2001.
    
    
14. Isackson, Cassandra.  Continuous Milled Shoulder Rumble Strips; Nationwide Survey.  Minnesota Department of Transportation,  February 2000.
    
    
15. Federal Highway Administration, Wyoming Division Office.  Shoulder Rumble Strips B Effectiveness and Current Practice.  April 1998.  Online Posting.  http://safety.fhwa.dot.gov/rumblestrips/effectiveness/wy.htm.  July 2000.
    
    
16. League for the Hard of Hearing.  Noise Levels in our Environment Fact Sheet.  March 1999.  Online Posting.  http://www.lhh.org/noise/decibel.htm.  October 1999.
    
    
17. Harwood, Douglas.  Use of Rumble Strips to Enhance Safety.  National Cooperative Highway Research Program, Synthesis of Highway Practice 191, 1993.
    
    
18. American Association of State Highway and Transportation Officials.  Guide for the Development of Bicycle Facilities.  Washington, D.C.  AASHTO, 1999.
    
    
19. Gårder, Per.  Rumble Strips or Not Along Wide Shoulders Designated for Bicycle Traffic? Transportation Research Record.  No. 1502, 1995, 1-7.
    
    
20. Arizona Department of Transportation.  Continuous Longitudinal Rumble Strips.  ADOT Traffic Engineering Policies, Guidelines, and Procedures.  Section 480.  2000.
    
    
21. Pennsylvania Department of Transportation.  Milled Shoulder Rumble Strips (MSRS); Safety Enhancement.  Memo from Michael Ryan, Deputy Secretary to District Engineers.  Dated April 21, 1995 with attachments.
    
    
22. Wyoming Department of Transportation.  Shoulder Rumble Strips.  Operating Policy.  No. 7-3.  1998.
    
    
23. New Mexico State Highway and Transportation Department.  Rumble Strip Guidelines.  1992.
    
    
24. Ohio Department of Transportation.  Rumble Strips.  Roadside Safety Devices.  Section 605.
    
    
25. Oklahoma Department of Transportation.  Rumble Strip Policy.  2000.
    
    
26. Minnesota Department of Transportation.  Rumble Strips on Shoulders of Rural Truck Highways.  Minnesota Department of Transportation Technical Memorandum.  No. 00-08-DS-01.  2000.
    
    
27. Washington Department of Transportation.  Rumble Strips.  Revised Code of Washington.  Section 46.61.160.
    
    
28. New York State Department of Transportation.  Safety shoulder Rumbles Strips (Safe-Strips) Policy and Revised Installation Details.  New York State.  Engineering Instruction 97-013.  1997.
    
    
29. Watts, G. R.  The Development of Rumble Areas as a Driver Alerting Device.  Supplementary Report No. 291.  Transport and Road Research Laboratory.  (1977).

• American Association of State Highway and Transportation Officials.  Guide for the Development of Bicycle Facilities.  Washington, D.C.  AASHTO, 1999.
  
  
• Arizona Department of Transportation.  Continuous Longitudinal Rumble Strips.  ADOT Traffic Engineering Policies, Guidelines, and Procedures.  Section 480.  2000.
  
  
• ASCE Human Powered Transportation Committee.  Comments TEA-21, October 30, 1998.  Online Posting: http://ourworld.compuserve.com/homepages/kbarrett/tea21.htm.  August 2000.
  
  
• ASCE Human Powered Transportation Committee.  Committee Meeting Minutes January 13 and 15, 1997. Online Posting: http://ourworld.compuserve.com/homepages/kbarrett/min_0197.htm.  August 2000.
  
  
• ASCE Human Powered Transportation Committee.  Committee Meeting Minutes January 12 and 14, 1998. Online Posting: http://ourworld.compuserve.com/homepages/kbarrett/min_0198.htm.  August 2000.
  
  
• ASCE Human Powered Transportation Committee.  Committee Meeting Minutes January 10, 1999. Online Posting: http://ourworld.compuserve.com/homepages/kbarrett/min_0199.htm.  August 2000.
  
  
• ASCE Human Powered Transportation Committee.  Update.  April 1999. Online Posting: http://ourworld.compuserve.com/homepages/kbarrett/upd_0499.htm.  August 2000.
  
  
• ASCE Human Powered Transportation Committee.  Update.  August 1996. Online Posting: http://ourworld.compuserve.com/homepages/kbarrett/upd_0896.htm.  August 2000.
  
  
• ASCE Human Powered Transportation Committee.  Update.  December 1997. Online Posting: http://ourworld.compuserve.com/homepages/kbarrett/upd_1297.htm.  August 2000.
  
  
• ASCE Human Powered Transportation Committee.  Update.  February 1997. Online Posting: http://ourworld.compuserve.com/homepages/kbarrett/upd_0297.htm.  August 2000.
  
  
• ASCE Human Powered Transportation Committee.  Update.  February 2000. Online Posting: http://ourworld.compuserve.com/homepages/kbarrett/upd_0200.htm.  August 2000.
  
  
• ASCE Human Powered Transportation Committee.  Update.  June 2000. Online Posting: http://ourworld.compuserve.com/homepages/kbarrett/upd_0500.htm.  August 2000.
  
  
• ASCE Human Powered Transportation Committee.  Update.  March 1998. Online Posting: http://ourworld.compuserve.com/homepages/kbarrett/upd_0398.htm.  August 2000.
  
  
• ASCE Human Powered Transportation Committee.  Update.  September 1997. Online Posting: http://ourworld.compuserve.com/homepages/kbarrett/upd_0997.htm.  August 2000.
  
  
• ASCE Human Powered Transportation Committee.  Update.  September 1998. Online Posting: http://ourworld.compuserve.com/homepages/kbarrett/upd_0998.htm.  August 2000.
  
  
• ASCE Human Powered Transportation Committee.  Update.  September 1999. Online Posting: http://ourworld.compuserve.com/homepages/kbarrett/upd_0999.htm.  August 2000.
  
  
• Bennett, R. Clarke.  FHWA Notice.  N 7560.9.  April 1987.  Online Posting.  http://www.bikeplan.com/rumble1.html.  July 2000.
  
  
• Bicycle Transportation Alliance.  Alert, Rumble Strips.  Online Posting. http://www.telepoert.com/~bta4bike/act/alert/a-rumble.htm.  July 2000.
  
  
• Bike Plan Source.  Comments on the AASHTO Guide for the Development of New Bicycle Facilities.  Online Posting.  http://www.bikeplan.com/guidedes.htm.  July 2000.
  
  
• California Department of Transportation.  Rumble Strips.  Caltrans Traffic Manual.  Section 6-03.2.  1999.
  
  
• California Department of Transportation.  Evaluation of Milled-In Rumble Strips, Rolled-In Rumble Strips and Proprietary Applications.  California State.  Draft Report.  February 2001.
  
  
• CH2MHILL.  Initial Draft of a Compendium of Strategies.  National Cooperative Highway Research Program, Project 17-18(3), September 2000, 4-1 4-10.
  
  
• Cheng, Eric, et al.  Application and Evaluation of Rumble Strips on Highways.  Utah Department of Transportation.  Online Posting.  http://safety.fhwa.dot.gov/rumblestrips/resources/chengite.htm.  August 2000.
  
  
• Chung.  A Study of Effectiveness of Various Shoulder Rumble Strips on Highway Safety.  Virginia Department of Transportation, 1994.
  
  
• Dorman, Frank.  VDOT Installs High Tech ‘Rumble Strips' on Smart Roads.  November 1999.  Online Posting.  http://www.vdot.state.va.us/info/News/state/1999/nrCO11231999_rumble.htm.  July 2000.
  
  
• Elefteriadoiu, L. et al.  Bicycle Tolerable Shoulder Rumble Strips.  Pennsylvania Department of Transportation, 2000.
  
  
• Federal Highway Administration, Wyoming Division Office.  Shoulder Rumble Strips B Effectiveness and Current Practice.  April 1998.  Online Posting.  http://safety.fhwa.dot.gov/rumblestrips/effectiveness/wy.htm.  July 2000.
  
  
• Federal Highway Administration.  Guidebook on Method to Estimate Non-Motorized Travel.  Report No. FHWA-RD-98-166, Federal Highway Administration, 1998.
  
  
• Federal Highway Administration.  Rumble Strip; Survey Summary Results.  Online Posting.  http://safety.fhwa.dot.gov/rumblestrips/resources/hqsurvey.htm.  August 2000.
  
  
• Federal Highway Administration.  Rumble Strips are LOUD!.  Online Posting:  http://safety.fhwa.dot.gov/fourthlevel/rumble/concern_noise.htm.  November 2000.
  
  
• Federal Highway Administration.  Rumble Strips; Bicycles and Things That Go Bump on the Road.  Online Posting.  http://safety.fhwa.dot.gov/rumblestrips/issues/bikeissues.htm.  July 2000.
  
  
• Federal Highway Administration.  Rumble Strips; Discussion Group; Rumble Strips and Bicycles.  October 1999.  Online Posting.  http://safety.fhwa.dot.gov/rumblestrips/communication/threads.cfm.  July 2000.
  
  
• Federal Highway Administration.  Rumble Strips; Technical Questions Received from Persons Communicating Via the Rumble Strip Web Site and Responses Given by Jim Growney, FHWA Rumble Strip Expert.  February 1999.  Online Posting.  http://safety.fhwa.dot.gov/rumblestrips/overview/maintenance2.htm.  July 2000.
  
  
• Federal Highway Administration.  Rumble Strips; The Four Types of Rumble Strips.  Online Posting.  http://safety.fhwa.dot.gov/rumblestrips/types.htm.  July 2000.
  
  
• FHWA Transporter.  July 2000, 5.  Online Posting.  http://www.roads.detr.gov.uk/roadnetwork/tirm/tal/traffic/11_93/item1.htm.  July 2000.
  
  
• Forkosh, Alan.  Rumble Strips B Act Now!  April 1999.  Online Posting.  http://www.ebbc.org/hypermail/ebbc-talk/1999/htm.  Discussion on East Bay Bicycle Coalition Talk.  July, 2000.
  
  
• Gårder, Per.  Rumble Strips or Not Along Wide Shoulders Designated for Bicycle Traffic? Transportation Research Record.  No. 1502, 1995, 1-7.
  
  
• Griffith, Michael.  Rolled-In Continuous Shoulder Rumble Strips Reduce ROR Crashes.
  
  
• Griffith, Michael.  Safety Evaluation of Continuous Shoulder Rumble Strips Installed on Freeways.  Transportation Research Record.  No. 1665, 1999, 28-34.
  
  
• Griffith, Michael.  Safety Evaluation of Roll-In Continuous Shoulder Rumble Strips on Freeways.  HSIS Report Summary Report FHWA-RD-00-032, December 1999.
  
  
• Harwood, Douglas.  Enhancing Highway Safety with Rumble Strips.  TR News.  No. 178, May-June 1995, 12-16.
  
  
• Harwood, Douglas.  Use of Rumble Strips to Enhance Safety.  National Cooperative Highway Research Program, Synthesis of Highway Practice 191, 1993.
  
  
• Hickey Jr., John.  Shoulder Rumble Strips Effectiveness; Drift-Off-Road Accident Reductions on the Pennsylvania Turnpike.  Transportation Research Record.  No. 1573, 1997, 105-109.
  
  
• Higgins, J. S. and W. Barbel.  Rumble Strip Noise.  Transportation Research Record.  No. 983, 1984, 27-36.
  
  
• Isackson, Cassandra.  Continuous Milled Shoulder Rumble Strips; Nationwide Survey.  Minnesota Department of Transportation,  February 2000.
  
  
• Khan, A. and A. Bacchus.  Economic Feasibility and Related Issues of Highway Shoulder Rumble Strips.  Transportation Research Record.  No. 1498, 1995, 92-101.
  
  
• Khan, A. M. and A. Bacchus.  Bicycle Use on Highway Shoulders.  Transportation Research Record.  No. 1502, 1995, 8-21.
  
  
• Kugler, B. Andrew, et al.  Highway Noise; A Design for Prediction and Control.  National Cooperative Highway Research Program.  Transportation Research Board, Synthesis 174, 1976.
  
  
• League for the Hard of Hearing.  Noise Levels in our Environment Fact Sheet.  March 1999.  Online Posting.  http://www.lhh.org/noise/decibel.htm.  October 1999.
  
  
• Ligon, Claude, et al.  Effects of Shoulder Textured Treatments on Safety.  Federal Highway Administration, FHWA/RD-85/027, 1985.
  
  
• Memphis City Schools.  Physics Tutorials; Sound; Decibel Levels Online Posting: http://www.memphis-schools.k12.tn.us/admin/tlapages/sound_decibel.htm.  October 2000.
  
  
• Minnesota Coalition of Bicyclists.  MCB Position Paper on ‘Run-Off-Road' Rumble Strips.  Online Posting.  http://www.winternet.com/~rtandems/mcb/ror1.thml.  July 2000.
  
  
• Minnesota Department of Transportation.  Rumble Strips on Shoulders of Rural Truck Highways.
  
  
• Minnesota Department of Transportation Technical Memorandum.  No. 00-08-DS-01.  2000.
  
  
• Moeur, Richard.  Analysis of Gap Patterns in Longitudinal Rumble Strips to Accommodate Bicycle Travel.  Transportation Research Record.  No. 1705, 2000, 93-98.
  
  
• Moeur, Richard.  What I (and Others) Have to Say About Cycling.  October 1999.  Online Posting.  http://members.aol.com/rcmoeur/opinbike.html.  July 2000.
  
  
• Morgan, Rick and Dan McAuliffe.  Effectiveness of Shoulder Rumble Strips: A Survey of Current Practice.  Report No. FHWA/NY/SR-97/127.  New York State Department of Transportation, 1997.
  
  
• National Center for Bicycling and Walking.  Rumble Strips; Grumblings on Rumble Strips: Perspectives from around the US.  Online Posting.  http://www.bikefed.org/rumble.htm.  August 2000.
  
  
• National Highway Traffic Safety Administration and National Center on Sleep Disorders Research.  A Report to Congress on the Collaboration Between the National Highway Traffic Safety Administration (NHTSA) and the National Center on Sleep Disorders Research (NCSDR). 1999.
  
  
• New Mexico State Highway and Transportation Department.  Rumble Strip Guidelines.  1992.
  
  
• New York State Department of Transportation.  Safety shoulder Rumbles Strips (Safe-Strips) Policy and Revised Installation Details.  New York State.  Engineering Instruction 97-013.  1997.
  
  
• O'hanlon, James and Gene Kelley.  A Psychophysiological Evaluation of Devices for Preventing Lane Drift and Run-Off-Road Accidents.  Technical Report No. 1736-F.  California Department of Transportation, 1974.
  
  
• Ohio Department of Transportation.  Rumble Strips.  Roadside Safety Devices.  Section 605.
  
  
• Oklahoma Department of Transportation.  Rumble Strip Policy.  2000.
  
  
• Pennsylvania Department of Transportation.  Milled Shoulder Rumble Strips (MSRS); Safety Enhancement.  Memo from Michael Ryan, Deputy Secretary to District Engineers.  Dated April 21, 1995 with attachments.
  
  
• Perrillo, Kerry.  The Effectiveness and Use of Continuous Rumble Strips.  August 1998.  Online Posting.  http://safety.fhwa.dot.gov/rumblestrips/resources.rumblekp.htm.  August 2000.
  
  
• Schimek, Paul.  The Dilemmas of Bicycle Planning.  Presented at the Association of Collegiate Schools of Planning.  July 1996.
  
  
• Snyder, Richard.  Bituminous Shoulder Rumble Strips.  Research Project 90-059, Pennsylvania Department of Transportation.  1994.
  
  
• Stonecypher, T. Lamar.  Rumble Strips; Victory.  June 2000.  Online Posting.  http://www.gate.net/~1stone/rumble.htm.  July 2000.
  
  
• Stutts, James.  Sleep Deprivation Countermeasures for Motorist Safety.  National Cooperative Highway Research Program.  Transportation Research Board, Synthesis 287, 2000.
  
  
• The Noise Center.  Noise Levels in our Environment Fact Sheet.  March 1999.  Online Posting: http://www.lhh.org/noise/decibel.htm.  October 2000.
  
  
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• Outcalt, William.  Bicycle-Friendly Rumble Strips.  Report No. CDOT-DTD-R-2001-4.  Colorado Department of Transportation, 2001.
  
  
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• Watts, G. R.  The Development of Rumble Areas as a Driver Alerting Device.  Supplementary Report No. 291.  Transport and Road Research Laboratory.  (1977).
  
  
• Williams, John.  Rumble Strips: A Growing Threat to America=s Cyclists?  Bicycle Forum.  Vol. 14, April 1987.
  
  
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• Wyoming Department of Transportation.  Shoulder Rumble Strips.  Operating Policy.  No. 7-3.  1998.