Guidelines for Selection of Speed Reduction Treatments at High-Speed Intersections: Supplement to NCHRP Report 613 (2008) / Chapter Skim
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From page 10... ...
NCHRP 3-74 Chapter 2 Selection of Speed Reduction Treatments at High-Speed Intersections Preliminary Findings Page2-1 2 Preliminary Findings 2.1 SPEED CONSIDERATIONS 2.1.1 Introduction Improving safety has long been a goal of the FHWA, NHTSA, AASHTO, ITE, and safety advocacy groups such as the Insurance Institute for Highway Safety. With over three million intersections (300,000 signalized)
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Chapter 2 NCHRP 3-74 Preliminary Findings Selection of Speed Reduction Treatments at High-Speed Intersections Page 2-2 • Geometric: The location where the typical section of the roadway segment is modified to create the intersection features. These modifications include tapers for adding or dropping lanes approaching and departing from the intersection.
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NCHRP 3-74 Chapter 2 Selection of Speed Reduction Treatments at High-Speed Intersections Preliminary Findings Page 2-3 maneuvers, crossing traffic, or queues) require drivers to be especially alert to the need to respond to these potential conflicts.
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Chapter 2 NCHRP 3-74 Preliminary Findings Selection of Speed Reduction Treatments at High-Speed Intersections Page 2-4 should be assessed when considering appropriate actions for retrofit projects. Such a design philosophy and approach can produce geometric conditions that are more likely to result in operating speeds consistent with driver expectations and commensurate with the roadways function.
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NCHRP 3-74 Chapter 2 Selection of Speed Reduction Treatments at High-Speed Intersections Preliminary Findings Page 2-5 uses to both maintain environmental quality and to provide necessary mobility. High-speed intersections can create a barrier to the mobility of non-auto users crossing the facility.
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Chapter 2 NCHRP 3-74 Preliminary Findings Selection of Speed Reduction Treatments at High-Speed Intersections Page 2-6 percentile speed. However, many studies have found that the likelihood of being involved in a crash increases with deviation from the mean speed of traffic on the facility (Taylor, 1965)
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NCHRP 3-74 Chapter 2 Selection of Speed Reduction Treatments at High-Speed Intersections Preliminary Findings Page 2-7 service. Vehicle speed within the influence area of intersections does not generally have a significant influence on overall travel time.
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Chapter 2 NCHRP 3-74 Preliminary Findings Selection of Speed Reduction Treatments at High-Speed Intersections Page 2-8 Exhibit 2-2 Roadway Facility Characteristics That May Affect Intersection Speed Intersection Variable Potential Relationship to Speed Facility Type Speeds tend to be higher on higher-order facilities. Speeds tend to be slightly lower when a raised median or no median is provided than when a depressed median or a two-way left-turn lane is present.
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From page 18... ...
NCHRP 3-74 Chapter 2 Selection of Speed Reduction Treatments at High-Speed Intersections Preliminary Findings Page 2-9 Exhibit 2-3 Intersection Characteristics That May Affect Intersection Speed Intersection Variable Potential Relationship to Speed Traffic Control /Approach Type A signalized intersection, a stop-controlled intersection, and a yield-controlled intersection require different driver tasks and operating speeds. Wayfinding Complex intersection maneuvers tend to reduce speeds, especially for unfamiliar drivers.
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From page 19... ...
Chapter 2 NCHRP 3-74 Preliminary Findings Selection of Speed Reduction Treatments at High-Speed Intersections Page 2-10 user behavior or evaluating traffic and safety data. 2.1.6.1 Common Conditions There are a variety of conditions that may be associated with a heightened sensitivity to speed.
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From page 20... ...
NCHRP 3-74 Chapter 2 Selection of Speed Reduction Treatments at High-Speed Intersections Preliminary Findings Page 2-11 2.1.6.4 Driver Behavior Undesirable driver behavior, such as lack of compliance with signals or stop signs, may indicate that excessive speeds approaching an intersection do not give drivers enough time to see and react to traffic control. The speeds may be the result of adaptation from the prior segment with drivers unaware of their speed and required stopping distances.
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From page 21... ...
Chapter 2 NCHRP 3-74 Preliminary Findings Selection of Speed Reduction Treatments at High-Speed Intersections Page 2-12 associated with specific geometric roadway and traffic volume conditions is the Highway Safety Information System (HSIS) database.
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NCHRP 3-74 Chapter 2 Selection of Speed Reduction Treatments at High-Speed Intersections Preliminary Findings Page 2-13 from HSIS, organizing the data, and setting up the analysis specs, and given the little return expected in advancing our knowledge and understanding of intersection types and their characteristics that are most affected by speeding and unsafe speed-related factors. A detailed HSIS database investigation and statistical analysis is outside of the scope of NCHRP 3-74 and was not be conducted as part of this work effort.
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From page 23... ...
Chapter 2 NCHRP 3-74 Preliminary Findings Selection of Speed Reduction Treatments at High-Speed Intersections Page 2-14 • Splitter islands • Speed tables • Reduced lane width • Visible shoulder treatments • Roadside Design Features In some cases, more than one treatment may be appropriate for a given intersection. To apply a treatment, users select a target speed and determine the location upstream of the intersection where sufficient distance is provided for drivers to react to potential conflicts related to the intersection when traveling at the target speed.
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From page 24... ...
NCHRP 3-74 Chapter 2 Selection of Speed Reduction Treatments at High-Speed Intersections Preliminary Findings Page 2-15 Dynamic warning signs have also been used to warn drivers of conflicting cross traffic at intersections. Called Collision Countermeasure Systems (CCS)
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From page 25... ...
Chapter 2 NCHRP 3-74 Preliminary Findings Selection of Speed Reduction Treatments at High-Speed Intersections Page 2-16 Exhibit 2-4 Dynamic Warning Sign (Photo: WSDOT) Exhibit 2-5 Dynamic curve-warning sign (Photo: TXDOT)
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From page 26... ...
NCHRP 3-74 Chapter 2 Selection of Speed Reduction Treatments at High-Speed Intersections Preliminary Findings Page 2-17 2.2.2.2 Treatment Layout/Design Dynamic warning signs placed in a location that provides adequate advance warning time for drivers to reduce their speed appropriately. The placement of a dynamic warning sign should be determined from estimated perception-reaction time, deceleration, and the stopping sight distance in advance of the intersection.
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Chapter 2 NCHRP 3-74 Preliminary Findings Selection of Speed Reduction Treatments at High-Speed Intersections Page 2-18 identified that prior to installation there had been 10 truck rollover crashes and after three years in operation, no rollover crashes had been reported.
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NCHRP 3-74 Chapter 2 Selection of Speed Reduction Treatments at High-Speed Intersections Preliminary Findings Page 2-19 2002)
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Chapter 2 NCHRP 3-74 Preliminary Findings Selection of Speed Reduction Treatments at High-Speed Intersections Page 2-20 markings were found to reduce mean speeds by 0.9 mph (standard error of 0.4 mph)
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NCHRP 3-74 Chapter 2 Selection of Speed Reduction Treatments at High-Speed Intersections Preliminary Findings Page 2-21 In another study that reduced crashes, transverse lines were applied at 42 approaches to roundabouts. Each approach had a minimum of 3.2 km (2 miles)
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From page 31... ...
Chapter 2 NCHRP 3-74 Preliminary Findings Selection of Speed Reduction Treatments at High-Speed Intersections Page 2-22 signals on high-speed roadways where drivers may not expect the presence of a signal. Transverse rumble strips are generally installed on approaches to intersections of expressways, rural highways, and parkways.
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From page 32... ...
NCHRP 3-74 Chapter 2 Selection of Speed Reduction Treatments at High-Speed Intersections Preliminary Findings Page 2-23 2.2.4.2 Treatment Layout/Design Rumble strips should be placed so that either the upcoming decision point, or a sign that identifies the action that may be required, is clearly visible as the driver passes over the rumble strip. Rumble strip locations should be selected to provide adequate advance warning time for drivers to take the potentially required action.
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From page 33... ...
Chapter 2 NCHRP 3-74 Preliminary Findings Selection of Speed Reduction Treatments at High-Speed Intersections Page 2-24 2.2.4.3 Speed Effects At the high-speed intersection approaches tested through NCHRP 3-74, rumble strips produced statistically significant speed reductions at the perception-response time data collection location, where a mean speed reduction of 1.3 mph (standard error of 0.5 mph) was observed.
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From page 34... ...
NCHRP 3-74 Chapter 2 Selection of Speed Reduction Treatments at High-Speed Intersections Preliminary Findings Page 2-25 2.2.5 Longitudinal Rumble Strips Overview Documented applications for high-speed intersections None Function Provide audible and tactile warning to reduce comfortable speed and minimize off-the-road and crossover crashes Applicability Rural undivided highways Design Variations Paved, rolled, or milled; raised or depressed; painted or not; cluster spacing Secondary Effects, Considerations Noise, motorcycle and bike impacts 2.2.5.1 Applicability and Considerations Like transverse rumble strips, longitudinal rumble strips are raised or grooved patterns installed on the roadway travel lane or shoulder pavements to warn drivers of an upcoming need to act. Longitudinal rumble strips are placed parallel to the direction of travel and may be located in the centerline or along the shoulder.
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From page 35... ...
Chapter 2 NCHRP 3-74 Preliminary Findings Selection of Speed Reduction Treatments at High-Speed Intersections Page 2-26 Exhibit 2-11 Centerline Rumble strips (Photo: MnDOT) Exhibit 2-12 Centerline Rumble Strips on the Centerline Pavement Markings (Photo: Torbic et al.)
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From page 36... ...
NCHRP 3-74 Chapter 2 Selection of Speed Reduction Treatments at High-Speed Intersections Preliminary Findings Page 2-27 deceleration rate. The distance should also be selected to work in concert with other treatments or features, such as warning signs.
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From page 37... ...
Chapter 2 NCHRP 3-74 Preliminary Findings Selection of Speed Reduction Treatments at High-Speed Intersections Page 2-28 2.2.6 Wider Longitudinal Pavement Markings Overview Documented applications for high-speed intersections None Function Increase intersection visibility, attract driver attention to intersection ahead Applicability Older drivers, lack of driver expectancy Design Variations Width, length, reflectivity Secondary Effects, Considerations Speed may increase with increased visibility 2.2.6.1 Applicability and Considerations Many departments of transportation increase the width of pavement markings to improve the visibility of centerline, lane line, and edge line striping and can provide added guidance to drivers from greater distances (Gates and Hawkins, 2002) (Hutchins, email)
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From page 38... ...
NCHRP 3-74 Chapter 2 Selection of Speed Reduction Treatments at High-Speed Intersections Preliminary Findings Page 2-29 Exhibit 2-14 Examples of wider longitudinal pavement markings in France 2.2.6.2 Treatment Layout/Design The placement and dimensions of wider longitudinal pavement markings on high-speed intersection approaches should be determined through a combination of a review of field conditions, driver sight lines and desired response, and local practice and judgment. The distance that the treatment extends from the intersection proper should be related to stopping sight distance and/or distance to achieve the desired deceleration at a comfortable deceleration rate.
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From page 39... ...
Chapter 2 NCHRP 3-74 Preliminary Findings Selection of Speed Reduction Treatments at High-Speed Intersections Page 2-30 use. There has been conclusive evidence to suggest that wider longitudinal pavement markings are easier for drivers to see, which can contribute to roadway safety (Gates, Chrysler, and Hawkins, 2002)
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From page 40... ...
NCHRP 3-74 Chapter 2 Selection of Speed Reduction Treatments at High-Speed Intersections Preliminary Findings Page 2-31 Exhibit 2-15 Single-lane roundabout (Photo: Oregon DOT) Roundabouts are appropriate for locations with a high crash frequency or severity, intersections where queues need to be minimized, intersections with irregular geometry, intersections that need to accommodate U-turns, and areas with a large amount of right-of-way available.
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From page 41... ...
Chapter 2 NCHRP 3-74 Preliminary Findings Selection of Speed Reduction Treatments at High-Speed Intersections Page 2-32 Exhibit 2-16 Key Roundabout Design Features (FHWA, Roundabouts: An Informational Guide, 2000) A mountable apron may be designed around the perimeter of the central island to provide additional width required for tracking through a single-lane roundabout.
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From page 42... ...
NCHRP 3-74 Chapter 2 Selection of Speed Reduction Treatments at High-Speed Intersections Preliminary Findings Page 2-33 relative safety benefits. Although the number of crashes and the severity of injuries were reduced at both single-lane and multi-lane roundabouts, a smaller reduction in total crashes was observed at the multi-lane roundabouts.
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From page 43... ...
Chapter 2 NCHRP 3-74 Preliminary Findings Selection of Speed Reduction Treatments at High-Speed Intersections Page 2-34 Exhibit 2-17 Approach Reverse Curvature (FHWA, Roundabouts: An Informational Guide, 2000)
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NCHRP 3-74 Chapter 2 Selection of Speed Reduction Treatments at High-Speed Intersections Preliminary Findings Page 2-35 Similar to roundabout design, approach curvature should be designed with an appropriate design vehicle to ensure that all trucks, buses, and emergency vehicles may traverse the approach without encroaching on the shoulder or adjacent sidewalks. 2.2.8.4 Speed Effects Current information about approach reverse curvature and how it impacts speed and safety relates exclusively to roundabouts.
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From page 45... ...
Chapter 2 NCHRP 3-74 Preliminary Findings Selection of Speed Reduction Treatments at High-Speed Intersections Page 2-36 Informational Guide, 2000) 2.2.9 Splitter Islands Overview Documented applications for high-speed intersections Roundabout intersection approaches and conventional intersection approaches in New Zealand and France Function Slow, direct, and separate conflicting traffic Applicability Stop- or yield-controlled approaches Design Variations Length, geometry, landscaping Secondary Effects, Considerations Splitter islands can provide refuge for pedestrians crossing at the intersection 2.2.9.1 Applicability and Considerations A splitter island is a raised or painted area on an intersection approach used to separate entering and exiting traffic, to deflect and slow entering traffic, and to provide refuge for pedestrians crossing the road in two stages (FHWA, Roundabouts: An Informational Guide, 2000)
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From page 46... ...
NCHRP 3-74 Chapter 2 Selection of Speed Reduction Treatments at High-Speed Intersections Preliminary Findings Page 2-37 minor approaches with other types of speed reduction treatments such as centerline rumble strips or pavement markings on major approaches at two-way stop-controlled intersections on rural highways. Exhibit 2-20 Splitter Island at a T-intersection in France 2.2.9.2 Treatment Layout/Design The length and geometry of splitter islands vary significantly.
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From page 47... ...
Chapter 2 NCHRP 3-74 Preliminary Findings Selection of Speed Reduction Treatments at High-Speed Intersections Page 2-38 Equipment, 1998)
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NCHRP 3-74 Chapter 2 Selection of Speed Reduction Treatments at High-Speed Intersections Preliminary Findings Page 2-39 both the daytime and nighttime. The majority of the reduction in injury crashes involved vehicles crossing paths at the intersection.
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Chapter 2 NCHRP 3-74 Preliminary Findings Selection of Speed Reduction Treatments at High-Speed Intersections Page 2-40 Exhibit 2-24 Speed table combined with textured pavement in Naples, FL (Photo: Fehr & Peers) Exhibit 2-25 Speed table combined with striping and colored concrete in Charlotte, NC (Photo: Fehr & Peers)
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NCHRP 3-74 Chapter 2 Selection of Speed Reduction Treatments at High-Speed Intersections Preliminary Findings Page 2-41 encounter the speed table at a high speed. The 1993 ITE Guidelines for the Design and Application of Speed Humps suggests that the first speed table in a series be placed no more than 200 feet from a stop sign or horizontal curve, and not within 250 feet of a traffic signal.
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Chapter 2 NCHRP 3-74 Preliminary Findings Selection of Speed Reduction Treatments at High-Speed Intersections Page 2-42 sites (ITE, 2007; Fehr & Peers, 2004)
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NCHRP 3-74 Chapter 2 Selection of Speed Reduction Treatments at High-Speed Intersections Preliminary Findings Page 2-43 Exhibit 2-27 Reduced Lane Width Road Bed Lane-width reductions have been used in both temporary and permanent applications. Permanent lane width reductions that reduce the overall pavement width are expected to have the greatest potential to reduce speeds because both the pavement width and the striping contribute to drivers perceptions of the roadway environment.
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From page 53... ...
Chapter 2 NCHRP 3-74 Preliminary Findings Selection of Speed Reduction Treatments at High-Speed Intersections Page 2-44 2.2.11.3 Speed Effects Research related to the speed, safety, and operational effects of reduced lane widths provides inconsistent results, indicating that the relationships are complex and difficult to evaluate without considering other elements of the intersection or roadway environment. Research and analysis conducted for NCHRP 3-72, which included both high-speed and lowspeed facilities, made the following conclusions regarding the speed effects of reduced lane widths: • Reduces mid-block speeds on four-lane arterials (average lane-width reduction of 2.7 feet associated with average speed reduction of 4 mph)
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From page 54... ...
NCHRP 3-74 Chapter 2 Selection of Speed Reduction Treatments at High-Speed Intersections Preliminary Findings Page 2-45 • Wider lanes may provide more room for correction maneuvers by drivers in nearcrash circumstances (Hauer, 2000)
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From page 55... ...
Chapter 2 NCHRP 3-74 Preliminary Findings Selection of Speed Reduction Treatments at High-Speed Intersections Page 2-46 Exhibit 2-28 shows an example of a visible shoulder treatment that used brick. Exhibit 2-28 Example of a shoulder composition application (Photo: Dan Burden)
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From page 56... ...
NCHRP 3-74 Chapter 2 Selection of Speed Reduction Treatments at High-Speed Intersections Preliminary Findings Page 2-47 2.2.13 Roadside Design Features Overview Documented applications for high-speed intersections None Function Reinforce transitioning environment, draw attention to multimodal users, reduce comfortable approach speeds Applicability Many applications Design Variations Roadside design features, gateways, and landscaping Secondary Effects, Considerations Sight distance 2.2.13.1 Applicability and Considerations The roadway environment can influence drivers perceptions of the road and provide safety benefits when implemented appropriately. Landscaping, cross-sectional changes, and gateways are three characteristics of the roadway environment that can affect the speed and safety of a roadway while providing aesthetically pleasing surroundings.
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From page 57... ...
Chapter 2 NCHRP 3-74 Preliminary Findings Selection of Speed Reduction Treatments at High-Speed Intersections Page 2-48 Exhibit 2-30 Gateway Maintaining landscaping treatments can be costly and difficult. Maintenance tasks can be labor and infrastructure intensive, and include mowing, pruning branches and shrubs, watering, and fertilizing.
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From page 58... ...
NCHRP 3-74 Chapter 2 Selection of Speed Reduction Treatments at High-Speed Intersections Preliminary Findings Page 2-49 Trees and vegetation can help define the edge of the roadway and slow traffic. Shinar, McDowell, and Rockwell (1974)
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From page 59... ...
Chapter 2 NCHRP 3-74 Preliminary Findings Selection of Speed Reduction Treatments at High-Speed Intersections Page 2-50 Exhibit 2-31 FHWA Low-Cost Treatment Concepts (FHWA, 2006) The objectives of the FHWA Low-Cost Intersection Treatments on High-Speed Rural Roads study were to identify, promote, and evaluate low-cost concepts to reduce speeds at intersections.
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From page 60... ...
NCHRP 3-74 Chapter 2 Selection of Speed Reduction Treatments at High-Speed Intersections Preliminary Findings Page 2-51 2.4 SPEED ENFORCEMENT 2.4.1 Overview Enforcement is critical to achieving compliance with speed limits (TRB Special Report 254, 1998)
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Chapter 2 NCHRP 3-74 Preliminary Findings Selection of Speed Reduction Treatments at High-Speed Intersections Page 2-52 drivers that enforcement is unpredictable. Whether to use stationary or moving police enforcement is another decision to make when choosing to use police enforcement.
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NCHRP 3-74 Chapter 2 Selection of Speed Reduction Treatments at High-Speed Intersections Preliminary Findings Page 2-53 communities. Speed enforcement could be used in conjunction with other countermeasures or as a single countermeasure.
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Chapter 2 NCHRP 3-74 Preliminary Findings Selection of Speed Reduction Treatments at High-Speed Intersections Page 2-54 Exhibit 2-32 List of Highway Agencies That Responded to Survey State highway agencies Alabama Mississippi Arizona Missouri California Montana Colorado Nevada Connecticut New Hampshire Delaware New Jersey Georgia New York Hawaii North Dakota Idaho Oklahoma Illinois Oregon Indiana Pennsylvania Iowa Rhode Island Kansas South Carolina Kentucky Tennessee Louisiana Vermont Maine Virginia Maryland Washington Michigan West Virginia Minnesota Wyoming 2.5.4 Summary of Survey Responses The highway agency responses to each question in the survey are summarized below. Where appropriate, the responses are tabulated.
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From page 64... ...
NCHRP 3-74 Chapter 2 Selection of Speed Reduction Treatments at High-Speed Intersections Preliminary Findings Page 2-55 indicating that they used a particular treatment were asked whether or not they found it to be effective and also whether it was currently in use. Exhibit 2-36 presents the responses to this question based on a list of typical treatments given in the survey.
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From page 65... ...
Chapter 2 NCHRP 3-74 Preliminary Findings Selection of Speed Reduction Treatments at High-Speed Intersections Page 2-56 Four of the nine agencies citing the use of these warning signs also indicated that they were found to be effective and currently in use; except in those cases where they are still being installed on a trial basis and effectiveness data is not available. Exhibit 2-34 Highway Agency use of Signing to Reduce Speeds Type of Sign No.
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From page 66... ...
NCHRP 3-74 Chapter 2 Selection of Speed Reduction Treatments at High-Speed Intersections Preliminary Findings Page 2-57 • Speed reduction sign specifications • Cost estimate table for speed reduction treatments for a specific project they have completed • Report on a study they published, entitled Optical Speed Bar Application Another respondent (Virginia) provided a one-page document with the specifications for signing and placing rumble strips on an intersection approach.
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From page 67... ...
Chapter 2 NCHRP 3-74 Preliminary Findings Selection of Speed Reduction Treatments at High-Speed Intersections Page 2-58 2.4.4.7 Question 7Potential Importance of an Effectiveness Evaluation Question 7 was designed to allow agencies to share their input about what speed reduction treatments they felt were most important to be evaluated to determine a level of effectiveness. This was accomplished by asking respondents to assign a numerical value to each treatment corresponding to its importance on a scale from 1 to 5.
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From page 68... ...
NCHRP 3-74 Chapter 2 Selection of Speed Reduction Treatments at High-Speed Intersections Preliminary Findings Page 2-59 are included for each treatment. Exhibit 2-37 Intersection Speed reduction Treatment Evaluation Criteria Rankings Intersection Speed reduction Treatment Average Value Min Value Max Value Mean or 85th percentile vehicle speed before vs.
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From page 69... ...
Chapter 2 NCHRP 3-74 Preliminary Findings Selection of Speed Reduction Treatments at High-Speed Intersections Page 2-60 2.4.4.10 Question 10Recently Installed Speed Reduction Treatments Question 10 asked highway agencies to provide a description of any treatments that have been installed in their jurisdiction in the last three years that they would be willing to have included in a future evaluation. Six agencies (16 percent of respondents)
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From page 70... ...
NCHRP 3-74 Chapter 2 Selection of Speed Reduction Treatments at High-Speed Intersections Preliminary Findings Page 2-61 Exhibit 2-39 Potential Speed Reduction Treatment Study Locations Treatments Total Pct (%) AZ CO LA IA MD MI MS MO NH NY PA VA WA WY Rumble strips in traveled way 11 73 X X X X X X X X X X X Wider centerline markings 7 47 X X X X X X X Wider edge line markings 7 47 X X X X X X X Dynamic warning signs activated by speed of vehicle 6 40 X X X X X X Transverse pavement markings on roadway 6 40 X X X X X X Reduced lane widths 5 33 X X X X X Roadside treatments 5 33 X X X X X Roundabouts 5 33 X X X X X Shoulder treatments 5 33 X X X X X Transverse pavement markings on shoulder 5 33 X X X X X Dynamic warning signs activated by conflicting vehicles 4 27 X X X X Roundabout-like Treatments 3 20 X X X Horizontal curvature on approach 2 13 X X Reverse horizontal curvature on approach 1 7 X Other 2 13 X X 2.4.4.12 Question 12Comments Question 12 asked highway agencies to provide additional comments, if desired.
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From page 71... ...
Chapter 2 NCHRP 3-74 Preliminary Findings Selection of Speed Reduction Treatments at High-Speed Intersections Page 2-62 • Oregon Oregon is interested in the results of this study, however to date we have little experience with many of the treatments mentioned above. Our most relevant experience is with the installation of a couple of roundabouts in Bend and Astoria as an alternative to signalization. • California We are starting a research effort regarding potentially assessing approaching vehicle speeds and adjusting signal time to reduce or eliminate dilemma zones. • Missouri We are bound by budget when agreeing to participate with (projects)
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From page 72... ...
NCHRP 3-74 Chapter 2 Selection of Speed Reduction Treatments at High-Speed Intersections Preliminary Findings Page 2-63 research on the topic had been undertaken. Rumble strips were identified as having the greatest need for evaluation based on their potential effectiveness.
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