Below is the uncorrected machine-read text of this chapter, intended to provide our own search engines and external engines with highly rich, chapter-representative searchable text of each book. Because it is UNCORRECTED material, please consider the following text as a useful but insufficient proxy for the authoritative book pages.
NCHRP 3-74 Chapter 3 Selection of Speed Reduction Treatments at High-Speed Intersections Testing Plan Page 3-1 3 Testing Plan 3.1 OVERVIEW This section contains the testing plan for speed reduction treatments investigated during Phase II of this project. The results of the literature review, state highway agency survey responses, and other testing considerations were assessed to establish priority treatments. The testing plan considered a variety of parameters and needs as well. 3.2 FOCUS OF TESTING PLAN The overall objectives of this research are to (1) identify or develop treatments and (2) develop guidelines for their selection to reduce the operating speed of vehicles approaching intersections, thereby reducing the frequency and severity of crashes. The Phase II testing quantified the speed effects of three treatments. This testing did not attempt to determine whether speed reduction treatments actually decrease the frequency and severity of crashes. It can take many years of measuring safety effects and conducting safety evaluations to adequately assess the short-, mid-, and long-term effects of a treatment. Such opportunities for analysis are not available within the limitations of this study. 3.3 RECOMMENDED TREATMENTS The research team ranked and prioritized the treatments based on published results and professional judgment. In addition, the research team evaluated the results of state highway agency surveys to understand each agencyÂs recommendations and priorities for implementing treatments. The research team correlated its treatment ranking with the survey results to develop primary, secondary, and alternative choices for treatments. With a primary list established, each treatment was further evaluated to determine which specific treatments to recommend for testing. The process the research team used to identify recommended treatments is summarized in Appendix ÂEÂ. The treatments recommended for testing in Phase II were: ⢠Rumble Strips Rumble strips are raised or grooved patterns installed on travel lanes or shoulder pavement. The texture differs from pavement to produce both an audible warning and physical vibration when a vehicleÂs tires pass over them (FHWA Research and Tech., 2004). Rumble strips can be installed to warn drivers of an upcoming need to act, such as stop at a traffic signal, slow down at an intersection, change lanes in a work zone, or steer back into the roadway. Rumble strips often are installed in the travel lane prior to intersections that have high speeds or high potential for vehicle crashes (FHWA Safety, 2004). Some agencies paint over rumble strips to make them more visible (FHWA Research and Tech., 2004). ⢠Transverse Pavement Markings Transverse pavement markings are placed perpendicular to the flow of traffic and appear as full
Chapter 3 NCHRP 3-74 Testing Plan Selection of Speed Reduction Treatments at High-Speed Intersections Page 3-2 transverse bars, peripheral transverse bars, or transverse chevrons. Transverse pavement markings are thought to potentially reduce vehicle speeds by giving drivers the perception that they are traveling faster than they really are or creating the perception of a narrowing roadway. ⢠Approach Reverse Curvature Approach curvature is a geometric design treatment that can be used at high-speed intersection approaches to force a reduction in vehicle speed though the introduction of geometric curvature. Approach reverse curvature consists of successive curves with progressively smaller radii. Research and applications of approach curvature have focused on roundabouts; however, this geometric design treatment could potentially be applied to conventional intersections. ⢠Dynamic Warning Signs Dynamic warning signs are placed near the roadway prior to a location that requires a warning or speed reduction. The messages are activated by approaching vehicles traveling a pre-determined speed (i.e. 5 mph above the posted speed). Typically, this type of system combines a radar device or pavement loop detectors with a variable message sign. The system measures the speed of the approaching vehicle and then provides a message to drivers who are traveling above pre- determined speeds. Examples of the messages displayed include, ÂSlow Down, ÂXX mph Curve Ahead, ÂYour Speed XX mph or ÂTraffic Ahead. 3.4 EXPERIMENTAL PLAN A Âbefore-and-after approach was used to evaluate the effect each treatment has on speed. Speeds were measured at selected locations on the intersection approach before and after the subject treatments were implemented. The Âafter measurements were taken a minimum of three months following a treatmentÂs installation. This acclimation period allowed the novelty of the treatments to subside and motorists to adjust to their presence. 3.5 SITE SELECTION This research project funded the treatment tests; however, the cost to install the treatment was the responsibility of the state or county agency involved. Therefore, the research team contacted various individuals and groups to identify states or counties that were interested in participating in the research and/or had plans to install a speed reduction treatment. These included: ⢠State agencies from the survey conducted during Phase I of the research ⢠Transportation agency colleagues of the research team ⢠Members of the NCHRP Panel ⢠Transportation professors ⢠Treatment vendors
NCHRP 3-74 Chapter 3 Selection of Speed Reduction Treatments at High-Speed Intersections Testing Plan Page 3-3 The research team first contacted the state agencies that participated in the survey. However, the team found that many of the agency staff listed on the survey were not aware of treatments being installed or of projects whose construction was going to correspond with the timeline of this research project. The team found the most effective way to identify potential treatment locations was to speak with a stateÂs regional or district staff most familiar with specific intersections and roadways in their area. In some cases, the agency staff did not have plans to install a treatment, but knew of Âproblem intersections where they would be willing to test a treatment. In those cases, the research team worked with agencies to suggest potential treatments to reduce speeds. The research team also worked with agencies to help identify other high-speed intersections that might benefit from speed reduction and at which the agency was willing to install the subject treatment. When initial contact was made with agencies regarding possible treatments, the research team requested the following information to become familiar with the agencies policies, potential sites, and speed and/or safety issues they were experiencing: ⢠The agency's interest in participating in NCHRP 3-74 testing ⢠Specific treatments the agency was willing to install and test ⢠Intersections with known speed or safety issues ⢠Specific project or intersection information ⢠Project type ⢠Location ⢠Documented problems (crashes, speed, complaints from neighbors, etc.) ⢠Construction season and installation schedule The extensive coordination effort identified 16 potential sites in five states and counties around the United States. Exhibit 3-1 shows the list of candidate sites identified.
Chapter 3 NCHRP 3-74 Testing Plan Selection of Speed Reduction Treatments at High-Speed Intersections Page 3-4 Exhibit 3-1 Preliminary List of Treatment Sites State/County Agency Contact Site 1 Whiskey Hill Road/Meridian Road (south of Aurora, OR) 2 Canby-Marquam Highway/Lone Elder Road (south of Canby, OR) 3 Redland Road/Bradley Road (east of Oregon City, OR) 4 Redland Road/Ferguson Road (east of Oregon City, OR) 5 Canby-Marquam Highway/Barnards Road (west of Molalla, OR) Clackamas County Joe Marek 6 Canby-Marquam Highway/Macksburg Road (south of Canby, OR) Bruce Erickson Oregon DOT Angela Kargel 7 OR 6/Wilson River Loop Road (near Tillamook, OR) 8 US 2/School Street (west of Wenatchee, WA) Washington DOT George Stuart 9 SR 26/SR 24/1st Street (near Othello, WA) 10 SR 20/Marysville Road (near Marysville, CA) 11 SR 12/Terminous Road Caltrans Gary Dossey 12 SR12/Brannan Island Road 13 US82 @ SH98 (Bowie County) 14 US271 @ FM726 (Upshur County) 15 US271 @ FM593 (Upshur County) Texas DOT Carlos Ibarra 16 US271 @ FM2088 (Upshur County)
NCHRP 3-74 Chapter 3 Selection of Speed Reduction Treatments at High-Speed Intersections Testing Plan Page 3-5 Once an agency identified one or more potential sites, the research team requested additional information to assess whether the sites were appropriate to test, what type of safety or speed issues existed, what type of treatment might be most effective, and where the treatment could be installed. The following information was requested for each potential testing location: ⢠Intersection and roadway as-builts or layouts that illustrated the plan and profile of the facilities ⢠Aerial photos of the intersection and surrounding area ⢠Crash data ⢠Speed data (e.g. spot speed studies, 85th Percentile speed, Posted Speed) ⢠Traffic volume data (e.g. ADT or intersection turning movement counts) After reviewing the information, the research team also found it helpful to speak directly with a state or county staff member to discuss the issues impacting each location. When feasible, the research team conducted site visits to collect additional data and take pictures to help determine the most effective testing plan. This site screening process refined the list of potential sites and screened sites that did not seem to meet the research objectives. Some potential sites were removed for the following reasons: ⢠Canby-Marquam Highway/Macksburg Road - This site was identified because of frequent run-off-the-road crashes. Therefore, Clackamas County was interested in installing a treatment to reduce vehicle speeds prior to the intersection. However, a closer review of the roadway geometry revealed that the crashes were most likely due to a curvature at the intersection rather than high speeds. The roadÂs alignment makes it difficult for drivers to observe the impending curve, and the presence of an intersection may not impact the number of crashes. Although a speed reduction treatment may help slow vehicles as they approach the intersection, the team decided not to include this site because speed is not the primary problem. ⢠Canby-Marquam Highway/Barnards Road - This site experiences frequent crashes due to vehicles violating the stop sign on the minor approach. The research team worked with Clackamas County to identify treatments that may reduce speeds at this intersection. However, a fatal crash occurred during the coordination process, which led to the installation of an immediate treatment. Therefore, the research team was unable to include this site because the treatmentÂs implementation did not coincide with the testing timeline. ⢠SR 12/Terminous Road and SR 12/Brannan Island Road - Caltrans identified these intersections as potential treatment sites due to high speeds and crash frequency. However, when the research team reviewed the intersection characteristics and aerials, it appeared that the issues affecting this intersection were most likely due to the unique intersection geometry. Therefore, the team decided not to include these sites in the testing.
Chapter 3 NCHRP 3-74 Testing Plan Selection of Speed Reduction Treatments at High-Speed Intersections Page 3-6 ⢠SR 20/Marysville Road - The research team and Caltrans worked together to identify this candidate site, conduct Âbefore testing, and select and design an appropriate treatment. However, Caltrans was not able to purchase and install the treatment in time to be included in our testing. Therefore, the team was not able to include this site. ⢠US 2/School Street - The Washington Department of Transportation identified this site due to frequent crashes and a high percentage of drivers exceeding the posted speed limits. The research team coordinated closely with WSDOT to identify appropriate treatments and designs. However, WSDOT also was modifying the speed limit signs and locations near this intersection. The signs were not installed soon enough for us to provide the appropriate acclimation period prior to the research testing. Therefore, the team was not able to include this site. After the candidate site screening process, the research team was able to confirm 10 testing sites in Oregon, Washington, and Texas. Exhibit 3-2 shows the final list of testing sites. Exhibit 3-2 Final List of Treatment Sites State/County Agency Contact Site 1 Whiskey Hill Road/Meridian Road (south of Aurora, OR) 2 Canby-Marquam Highway/Lone Elder Road (south of Canby, OR) 3 Redland Road/Bradley Road (east of Oregon City, OR) Clackamas County, Oregon Joe Marek 4 Redland Road/Ferguson Road (east of Oregon City, OR) Bruce Erickson Oregon DOT Angela Kargel 5 OR 6/Wilson River Loop Road (near Tillamook, OR) Washington DOT Robert Stull 6 SR 26/SR 24/1st Street (near Othello, WA) 7 US82 @ SH98 (Bowie County) 8 US271 @ FM726 (Upshur County) 9 US271 @ FM593 (Upshur County) Texas DOT Carlos Ibarra 10 US271 @ FM2088 (Upshur County)
NCHRP 3-74 Chapter 3 Selection of Speed Reduction Treatments at High-Speed Intersections Testing Plan Page 3-7 3.6 TREATMENT SELECTION Once the sites were chosen, the research team worked closely with the respective state or county agencies and used the information gathered during the site selection process to identify appropriate treatments for each site. The following section provides an overview of the treatment selection process. 3.6.1. Pre-Screening As part of the pre-screening process, gathering data such as crash history, speed study results and aerial images can be helpful in gaining an understanding of the site context. This includes the relationships between the segment and intersection as well as the influence of the geometry and environment. An understanding of these elements can help determine whether speed is the primary cause of problems experienced at a particular location. STEP 1. Identify intersection in need of improvement o Crashes (number) o Crashes (severity) o Crashes (type) Rear-end crashes may indicate a need for separate left-turn or right-turn lanes on the main line Angle crashes may indicate gap acceptance or intersection sight-distance issues Single-vehicle crashes, including those involving a traffic-control violation, may indicate speed adaptation or intersection-awareness issues Crashes at night may indicate a need for illumination o Reports of high speed o Near misses (operations) STEP 2. Gather intersection information o Intersection features o Crash history o Speed data o Traffic volumes o Traffic composition
Chapter 3 NCHRP 3-74 Testing Plan Selection of Speed Reduction Treatments at High-Speed Intersections Page 3-8 o Aerial images o Site visit STEP 3. Assess Data o What is the primary problem? o Is speed a contributing factor or should other factors be considered? o What can be learned anecdotally from agency staff? 3.6.2. Treatment Screening After the pre-screening process verifies that speed is a primary cause, the treatment screening process can help identify Âfatal flaws to eliminate candidate treatments. In some cases, Âfatal flaw treatments may be identified because of cost reasons, agency policies, or existing intersection characteristics. STEP 4. Identify Fatal Flaws o Cost  funding issues may prevent installing a dynamic warning sign or approach curvature. o Time to implement  some treatments take longer to install than others and some can only be installed during certain weather conditions. o Noise considerations  rumble strips may be undesirable in residential areas due to noise. o Right-of-way  approach curvature may require right-of-way. o Energy/power source  dynamic warning signs require a power source. o Land use and environment  existing driveway locations may prohibit some types of treatments. o Policy  some jurisdictions may have policies that prohibit some treatments. o Novelty  depending on the user (commuter vs. recreational), some treatments are more prone to having novelty effects. STEP 5. Evaluate Potential Treatments â What are the objectives? After the list of treatments has been defined, the next step is to gain additional information regarding the remaining potential treatments and determine their objectives. These objectives can include where speeds should be reduced and by how much.
NCHRP 3-74 Chapter 3 Selection of Speed Reduction Treatments at High-Speed Intersections Testing Plan Page 3-9 ⢠What information is available about each treatment? o Has there been any past research conducted on that particular treatment? Was the treatment effective? Were there any side effects of the treatment? o Does the agency have experience with installing this type of treatment? ⢠How much speed reduction is desired? o What is the target speed? o Extensively reducing speeds may require more prominent treatments such as an approach curvature, a dynamic warning sign or rumble strips. Other treatments may have a lesser impact on speeds. ⢠Where should speed be reduced? o If speed reduction is only needed at the intersection, an approach curvature may be implemented. However, transverse pavement markings may require a longer distance to reduce speeds. 3.6.3. Candidate Site Treatments This treatment selection process was conducted at all of the sites in Oregon and Washington. For the site in Texas, the research team collaborated with TXDOT staff to determine appropriate treatments based on the agencyÂs interest and the needs of the research project. Exhibit 3-3 shows the final list of candidate sites and the treatments that were selected for each site
Chapter 3 NCHRP 3-74 Testing Plan Selection of Speed Reduction Treatments at High-Speed Intersections Page 3-10 Exhibit 3-3 Candidate Sites and Treatment Selections State/County Agency Site Treatment 1 Whiskey Hill Road/Meridian Road (south of Aurora, OR) Transverse Pavement Markings 2 Canby-Marquam Highway/Lone Elder Road (south of Canby, OR) Transverse Pavement Markings 3 Redland Road/Bradley Road (east of Oregon City, OR) Transverse Pavement Markings Clackamas County, Oregon 4 Redland Road/Ferguson Road (east of Oregon City, OR) Transverse Pavement Markings Oregon DOT 5 OR 6/Wilson River Loop Road (near Tillamook, OR) Transverse Pavement Marking Washington DOT 6 SR 26/SR 24/1st Street (near Othello, WA) Dynamic Warning Sign 7 US82 @ SH98 (Bowie County) Dynamic Warning Sign 8 US271 @ FM726 (Upshur County) Rumble Strips 9 US271 @ FM593 (Upshur County) Rumble Strips Texas DOT 10 US271 @ FM2088 (Upshur County) Rumble Strips The research team made extensive efforts to identify sites that would allow testing of an even mix of treatments. However, based on the agencies preference for treatments, funding issues, and/or construction abilities, the research team had to adapt to each agencyÂs needs and installation plans when selecting each siteÂs treatments. Exhibit 3-4 shows the mix of treatments that were installed and tested for this research project. Exhibit 3-4 Mix of Treatments Treatment Number of Testing Sites Transverse Pavement Markings 5 Dynamic Warning Signs 2 Rumble Strips 3 Approach Curvature 0 Transverse pavement markings were the most popular treatment tested because of their low cost, low maintenance requirements, and ease of installation. Some states were hesitant to install rumble strips because of potential noise impacts on adjacent properties. Dynamic warning signs received a high level of interest from state and county agencies. However, their cost - $18,000 to
NCHRP 3-74 Chapter 3 Selection of Speed Reduction Treatments at High-Speed Intersections Testing Plan Page 3-11 $20,000 - deterred many states from pursuing this treatment. Approach curvature also was prohibitive as a treatment because it requires construction and is more costly than other treatments, based on the need for roadway widening and partial roadway reconstruction in some cases. In collaboration with Clackamas County, the research team identified that approach curvature could be an appropriate treatment to install at a site south of Canby, Oregon. Clackamas County surveyed the intersection to provide the research team with detailed intersection and roadway information to allow the research team to finalize the approach curvature design. However, upon reviewing the survey, the research team and Clackamas County determined that there was a significant amount of right-of-way that would need to be acquired to install this type of treatment. Due to the countyÂs inability to acquire the right-of-way and the high installation costs, the county could not install this treatment. The research team was not able to identify any other candidate sites for approach curvature, so this treatment was not included in the testing. 3.7 TREATMENT LAYOUTS After the treatment selection process was completed and a treatment was identified for each site, the team used aerial images and the existing roadway and intersection features to identify appropriate locations for the treatment installations. 3.7.1. Implementing Treatments ⢠Identify existing roadway features  existing signs, pavement markings, driveways, and curvature may affect treatments and treatment configurations ⢠Apply treatments to roadway  how well do they match the existing features? o Placing a treatment near an existing sign, such as an Âintersection ahead sign, could provide another visual cue to drivers to reduce their speeds and increase driver awareness of the impending intersection. o Placing a treatment at a location where the roadway changes, such as the point of tangency, may provide a cue to the driver that the roadway environment is changing and a speed reduction is necessary. ⢠Adapt and customize o If adequate stopping sight distance (SSD) and an upstream Âintersection ahead sign are present, treatments may be applied at both locations. However, if the SSD is at the same location as the Âintersection ahead sign, then one set of treatments may be sufficient. For the majority of the sites, treatment schematics were developed to illustrate the appropriate treatment implementation locations. Exhibits 3-5 to 3-9 contain the treatment schematics for each site in Oregon and Washington. These figures were submitted to each agency for consideration.
Chapter 3 NCHRP 3-74 Testing Plan Selection of Speed Reduction Treatments at High-Speed Intersections Page 3-12 Exhibit 3-5
NCHRP 3-74 Chapter 3 Selection of Speed Reduction Treatments at High-Speed Intersections Testing Plan Kittelson& Associates, Inc. Page 3-13 Exhibit 3-6
Chapter 3 NCHRP 3-74 Testing Plan Selection of Speed Reduction Treatments at High-Speed Intersections Page 3-14 Exhibit 3-7
NCHRP 3-74 Chapter 3 Selection of Speed Reduction Treatments at High-Speed Intersections Testing Plan Kittelson& Associates, Inc. Page 3-15 Exhibit 3-8
NCHRP 3-74 Chapter 3 Selection of Speed Reduction Treatments at High-Speed Intersections Testing Plan Exhibit 3-9 Page 3-16
Chapter 3 NCHRP 3-74 Testing Plan Selection of Speed Reduction Treatments at High-Speed Intersections For the sites in Texas, TXDOT took an active role in determining the treatment placements by incorporating its standard policies for installing rumble strips and dynamic warning signs. Therefore, the research team did not develop treatment schematics for these intersections. Exhibits 3-10 and 3-11 contain a schematic of the rumble strip and dynamic warning sign layout used at the site in Texas. In all cases, the research team adapted to the specific needs of the agencies. For example, ODOT and WSDOT preferred that the research team provide treatment installation recommendations for review. Clackamas County and TXDOT staff showed an interest in being more engaged and took a more active role in determining potential treatment types and placements. Overall, the research teamÂs collaborative and adaptive approach to each agencyÂs needs provided a positive testing program. 3.8 TREATMENT DESIGNS In addition to the treatment layout schematics, the research team also designed some of the treatments for specific sites. The following section describes the treatment designs for the transverse pavement markings, dynamic warning signs, and rumble strips. 3.8.1. Transverse Pavement Markings Exhibit 3-12 illustrates the peripheral transverse pavement marking design proposed for the sites. As shown in this figure, the design includes five pavement markings placed in a series and spaced approximately 15 feet apart. Each marking is approximately 12 to 24 inches wide and between 18 to 33 inches long. The length of each peripheral bar depended on the existing lane width and the width of the wheel base for vehicles that commonly travel through the area. The peripheral bars were designed to extend perpendicularly into travel lanes from the edge and center lines, but not to extend into the vehicles wheel path. For example, peripheral bars placed on a roadway with a 12-foot travel lane that serves trucks with a 9-foot wheel base were designed to be 18 inches long. The actual treatment applications were defined and implemented based on the site specific conditions. Because the pavement markings did not extend into the wheel path, there is less maintenance, material, and expense, and the markings do not create a slick surface when wet. This type of pavement marking is intended to give drivers the perception that they are traveling faster than they are or that the travel lane is narrowing, thereby promoting speed reduction. In addition, this type of treatment also can supplement existing signs to help drivers be aware that an intersection is ahead. Kittelson& Associates, Inc. Page 3-17
Chapter 3 NCHRP 3-74 Testing Plan Selection of Speed Reduction Treatments at High-Speed Intersections Page 3-18 Kittelson & Associates, Inc. Exhibit 3-10
NCHRP 3-74 Chapter 3 Selection of Speed Reduction Treatments at High-Speed Intersections Testing Plan Kittelson& Associates, Inc. Page 3-19 Exhibit 3-11
Chapter 3 NCHRP 3-74 Testing Plan Selection of Speed Reduction Treatments at High-Speed Intersections Page 3-20 Kittelson & Associates, Inc. Exhibit 3-12
NCHRP 3-74 Chapter 3 Selection of Speed Reduction Treatments at High-Speed Intersections Testing Plan Kittelson& Associates, Inc. Page 3-21 A dynamic warning sign was chosen for the SR 26/SR 24/1st Street intersection near Othello, Washington. The research team provided WSDOT with a variety of possible designs that showed various display messages, sizes, and costs. WSDOT chose to design its own dynamic warning sign, which included the following features: ⢠ÂSpeed Limit 50 sign ⢠ÂIntersection Ahead symbol ⢠Dynamic message that flashes ÂSLOW (1.5 seconds), ÂDOWN (1.5 seconds) and then is blank for 1.5 seconds. Exhibits 3-13 to 3-16 illustrate the dynamic warning sign designed by WSDOT. Exhibit 3-13 Dynamic Warning Sign Design Exhibit 3-14 Dynamic Warning Sign Design
Chapter 3 NCHRP 3-74 Testing Plan Selection of Speed Reduction Treatments at High-Speed Intersections Page 3-22 Kittelson & Associates, Inc. Exhibit 3-15 Dynamic warning sign installed by WSDOT. Dynamic warning signs are activated by a maximum or target speed that is established in a radar unit or loop detector. WSDOT chose to use a radar unit that was attached to the sign, as shown in Exhibit 3-16. WSDOT, in coordination with the research team, chose a target speed of 54 mph to alert drivers that they are approaching a posted speed limit of 55 mph. This dynamic warning sign does not display the running speed of passing vehicles. Exhibit 3-16 Radar Unit A dynamic warning sign also was chosen for the US82/SH98 intersection in Bowie County, Texas, and is illustrated in Exhibit 3-17.
NCHRP 3-74 Chapter 3 Selection of Speed Reduction Treatments at High-Speed Intersections Testing Plan Kittelson& Associates, Inc. Page 3-23 Exhibit 3-17 TXDOT Dynamic Warning Sign Design As shown here, the TXDOT treatment consisted of a posted speed limit sign and a dynamic sign below that displays the speeds of vehicles as they pass. The speeds were measured using a built- in radar detector and a built-in processor within the radar unit.
Chapter 3 NCHRP 3-74 Testing Plan Selection of Speed Reduction Treatments at High-Speed Intersections Page 3-24 Kittelson & Associates, Inc. 3.8.1. Rumble Strips Rumble strip treatments were selected for three sites in Upshur County, Texas: ⢠US 271/FM726 ⢠US271/FM593 ⢠US271/FM2088 Exhibit 3-18 illustrates the design that was incorporated based on TXDOTÂs policy for installing rumble strips on state roads. Exhibit 3-18 Rumble Strip Design
NCHRP 3-74 Chapter 3 Selection of Speed Reduction Treatments at High-Speed Intersections Testing Plan Kittelson& Associates, Inc. Page 3-25 The rumble strip design included raised strips of plastic that were attached to the roadway. In addition, these strips were white to add a visual affect. Exhibit 3-19 shows the rumble strip design at one of the Texas sites. Exhibit 3-19 Rumble Strip Design The following case study, which describes how a specific speed reduction treatment was chosen to improve the Whiskey Hill Road/Meridian Road site in Clackamas County, Oregon, further illustrates the treatment selection and implementation process.
Chapter 3 NCHRP 3-74 Testing Plan Selection of Speed Reduction Treatments at High-Speed Intersections Page 3-26 Kittelson & Associates, Inc. CASE STUDY Whiskey Hill Road/Meridian Road Clackamas County, Oregon PRE-SCREENING 3.9.1.1. STEP 1. Identify intersection in need of improvement o Clackamas County identified this intersection because of speed and safety concerns. o Meridian Road - Complaints of people running the northbound stop sign. o Whiskey Hill Road - Horizontal curves, grade, and limited sight distance made it difficult to anticipate the upcoming intersection. o Special condition  There is a school adjacent to the intersection, which motorists also had difficulty anticipating. AuthorÂs Note: Clackamas County staff said speeds in this area were not extremely high, but drivers were traveling faster than desired. They also reported multiple complaints of drivers running the stop sign northbound on Meridian Road. This may have been caused by drivers inability to adapt to the intersection influence area and having insufficient distance to stop. In addition, staff from the adjacent school had received complaints of vehicles driving too fast. 3.9.1.2. STEP 2. Gather intersection information Traffic Volumes o There is approximately 2,100 ADT (average daily traffic) during a typical weekday on Whiskey Hill Road. o There is approximately 1,300 ADT during a typical weekday on Meridian Road. Traffic Composition o There is a high percentage of agricultural truck traffic and school buses traveling through the area.
NCHRP 3-74 Chapter 3 Selection of Speed Reduction Treatments at High-Speed Intersections Testing Plan Kittelson& Associates, Inc. Page 3-27 Intersection Features o This is a two-way, stop-controlled intersection, with stop signs on the north and south approaches of Meridian Road. o Whiskey Hill and Meridian roads are two-lane roadways. o The west approach of Whiskey Hill Road features a horizontal curve, sight- distance issues, and grade changes. Speed Data o Speed is defined according to the Âbasic rule (See ÂAuthorÂs Note below) o A speed study conducted in August 2005 found: Whiskey Hill Road 85th percentile speed = 48.7 mph Percent exceeding 45 mph = 28% Meridian Road 85th percentile speed = 56.2 mph Percent exceeding 45 mph = 66% o There are 25 mph school zones on the north approach of Meridian Road and the east approach of Whiskey Hill Road. AuthorÂs Note: Basic Rule = ÂNo person shall drive a vehicle at a speed greater than is reasonable and prudent under the conditions and having regard to the actual and potential hazards then existing. Based on discussions with the county, a speed of 45 mph was reasonable for each intersection approach. Crash Records o One crash was reported in 2004 and involved a vehicle running the stop sign. Environment o The surrounding area is rural. o An elementary school is located on the northeast corner of the intersection. o Lenhardt Airport is located north of the elementary school on Meridian Road.
Chapter 3 NCHRP 3-74 Testing Plan Selection of Speed Reduction Treatments at High-Speed Intersections Page 3-28 Kittelson & Associates, Inc. o A convenience store is located on the intersectionÂs southeast corner. o Single-family residences are situated adjacent to and east of Meridian Road and south of Whiskey Hill Road 3.9.1.3. STEP 3. Assess Data o Is speed the primary issue? Are speed reduction treatments needed? No speed limit is posted; therefore, the Âbasic rule applies. Given the residential driveways and school zone on Meridian Road, and the horizontal curvature, grade changes, and limited sight distance on Whiskey Hill Road, 45 mph is a reasonable speed for these roadways. Based on the speed data for Meridian Road and Whiskey Hill Road, approximately 66 % and 28 % of drivers exceeded 45 mph, respectively. o On which approaches is speed reduction needed? Based on crash data and public complaints, there was a need to reduce speeds in the northbound direction on Meridian Road to eliminate stop- sign violations. Based on complex roadway geometry and limited sight distance, there was a need to reduce speeds in the eastbound direction prior to the intersection and school. AuthorÂs Note: The school is more visible to approaching drivers in the southbound and westbound direction. Therefore, no speed reduction treatments are needed on those approaches. TREATMENT SCREENING POTENTIAL TREATMENTS Reduced lane width Visible shoulder treatments Speed tables Rumble strips Roadway environment Approach curvature Roundabouts Splitter islands Longitudinal pavement markings Transverse pavement markings Dynamic warning sign 3.9.1.4. 3.9.1.5. STEP 4. Identify Fatal Flaws o Reduced Lane Width: Existing lane width is 11-feet. o Visible Shoulder Treatment: Existing study roadways have no shoulders.
NCHRP 3-74 Chapter 3 Selection of Speed Reduction Treatments at High-Speed Intersections Testing Plan Kittelson& Associates, Inc. Page 3-29 Exhibit 3-20 illustrates the limited shoulder and narrow cross-section on Meridian and Whiskey Hill roads. Exhibit 3-20 Limited Shoulder and Narrow Cross-Section o Speed Tables: 85th-percentile speeds are greater than 45 mph. Therefore, speed tables were not appropriate for these high-speed study roadways. o Rumble Strips: Clackamas County was not interested in installing rumble strips at this location due to potential noise impacts on nearby residences and the school. Exhibit 3-21 illustrates the existing residences near Whiskey Hill and Meridian roads. Exhibit 3-21 Existing Residences near Study Area o Roadway Environment: Existing vegetation and a continuous drainage ditch adjacent to the roadway made it difficult to install effective roadway environment treatments such as landscaping.
Chapter 3 NCHRP 3-74 Testing Plan Selection of Speed Reduction Treatments at High-Speed Intersections Page 3-30 Kittelson & Associates, Inc. Exhibit 3-22 illustrates the existing roadway vegetation on Meridian and Whiskey Hill roads. Exhibit 3-22 Existing Roadway Vegetation o Approach Curvature: The existing roadways have a narrow cross-section and right-of-way is constrained. o Roundabout: Clackamas County did not have funding available to consider a roundabout as a potential intersection treatment. In addition, existing roadways have narrow cross-sections and right-of-way is constrained. o Splitter Island: Existing roadways have narrow cross-sections and right-of-way is constrained. o Dynamic Warning Signs: Clackamas County did not have funding available to consider dynamic warning signs as a potential treatment. In addition, the rural location made it difficult and expensive to provide power to the signs. AuthorÂs Note: Clackamas County was interested in a treatment that would be implemented quickly and easily. However, the county had limited funding available for the treatment project. 3.9.1.6. STEP 5. Evaluate Potential Treatments Remaining Potential Treatments Reduced lane width Visible shoulder treatments Speed tables Rumble strips Roadway environment Approach curvature Roundabouts Splitter islands Longitudinal pavement markings Transverse pavement markings Dynamic warning sign After the research team identified the Âfatal flaw treatments that were not feasible to install at this intersection, two potential treatments remained: longitudinal and transverse pavement markings. At this point, the research team reviewed past research and evaluated each potential treatment to assess their effectiveness and determine which was the most appropriate.
NCHRP 3-74 Chapter 3 Selection of Speed Reduction Treatments at High-Speed Intersections Testing Plan Kittelson& Associates, Inc. Page 3-31 Longitudinal Pavement Markings o No research had been conducted to show this as an effective speed reduction treatment. o This treatment requires a large amount of pavement marking material, depending on the treatment boundary. o Longitudinal pavement markings may conflict with multiple adjacent driveways. o This solution may be more effective in areas with speed adaptation issues or a large number of elderly drivers. Transverse Pavement Markings o Past research has shown this treatment to be effective at reducing speeds. In addition to reviewing past research and treatment information, the research team also reviewed the objectives for the speed reduction, including the target speed and locations where speed reduction was desired. How much speed reduction is desired? o Eastbound direction: 45 mph is a safe speed to manoeuvre the curves and grade. o Northbound direction: 45 mph at Stopping Sight Distance (SSD) was recommended to reduce speeds at the intersectionÂs approach and throughout the school zone. Where should speed be reduced? o Speed reduction was needed at the eastbound and northbound intersection approaches, beginning approximately 500 feet (SSD) from the intersection. Based on the review of treatment information and the objectives for reducing speeds, the research team selected transverse pavement markings for this site.
Chapter 3 NCHRP 3-74 Testing Plan Selection of Speed Reduction Treatments at High-Speed Intersections Page 3-32 Kittelson & Associates, Inc. TREATMENT IMPLEMENTATION As shown previously, Exhibit 3-5 illustrates a schematic of the proposed treatment layouts at the Whiskey Hill Road/Meridian Road intersection. Meridian Road (south approach) o Treatment Location #1: ÂSchool Ahead sign at milepost 4.12 Stopping sight distance at 55 mph is also near milepost 4.12 (approximately 500 feet from the intersection) o Treatment Location #2: 400 feet downstream(?) of the ÂSchool Ahead sign and after the existing driveways on Meridian Road Whiskey Hill Road (west approach) o Treatment Location #1: ÂIntersection Ahead sign at milepost 1.41 o Treatment Location #2: Approximate point of curvature at milepost 1.47 The installation points closest to the intersection (mileposts 4.12 and 1.41) were chosen because of the existing signs at those location and because the signs are near the stopping sight distance for 55 mph (495 feet, Exhibit 3-1 in AASHTO). The existing signs currently serve to alert drivers of the upcoming intersection. The markings have the potential to draw additional attention to those warning signs and encourage drivers to reduce their speed as they approach the intersection. The installation points beyond the upstream(?) treatments are located where the roadway environment changes, such as the approximate point of curvature (Whiskey Hill Road, milepost 1.47) or presence of driveways (Meridian Road, milepost 4.21). In addition, placing a treatment at the end of the tangent at the point of curvature on a roadway allowed drivers a consistent view of the treatment ahead.
NCHRP 3-74 Chapter 3 Selection of Speed Reduction Treatments at High-Speed Intersections Testing Plan Kittelson& Associates, Inc. Page 3-33 3.10. DATA COLLECTION METHODOLOGY 3.10.1. Overview The research team considered a variety of testing methodologies, including field testing, controlled off-road testing, and driving simulators. The primary objective of any testing methodology is to get meaningful data on the speed reduction capabilities of potential treatments. The research team contacted driving simulator operators and requested information on those facilities ability to conduct meaningful tests on the four recommended treatments. The responses supported the promise of potential simulator applications but also described limitations in testing some treatments. Field tests would yield results from real-world drivers with real-world trip purposes, driving a variety of vehicle types. These drivers will generally be unaware that a test is being conducted. Driving simulators would use drivers in a lab with no trip purpose, and those drivers are aware that some sort of test is being conducted (although they should not know what specifically is being tested). These participants would be Âdriving a single vehicle type versus the variety of vehicles in applied field tests. It is intuitive that some participants in the driver simulators would pay more attention to the task of driving than would real-world drivers. Simulator participants would encounter the treatments for the first time and may react more cautiously than if they encountered them at the same location on a regular basis. The research team expected to get more data points from field tests and have the ability to adapt the tests to site-specific needs. Finally, field tests could be implemented and monitored after motorists acclimated to the treatments. This research approach would provide opportunities to understand the long-term speed reduction implications and conduct before-and-after evaluations at a specific site. The research team recognized the value and potential application of driver simulators, but determined field tests would provide the most meaningful data. 3.10.2. Equipment The research team investigated various data collection equipment and procedures to determine the most comprehensive and effective means of collecting speed data during field testing. The methodologies that were investigated are: Hi-Star devices, tape switches, and video photography. Prior to the investigation, the team identified three key features that must be achieved by the device to produce the type of data required for this research: ⢠It must be possible to establish a common time base for data collected by different units along the intersection approach so that speed profiles of individual vehicles could be determined. ⢠Speed and headway data must be collected and stored for each individual vehicle detected, not placed in Âbins by speed or headway category.
Chapter 3 NCHRP 3-74 Testing Plan Selection of Speed Reduction Treatments at High-Speed Intersections Page 3-34 Kittelson & Associates, Inc. ⢠Each device must have speed and headway data accuracies to ensure that even minimal speed effects of various treatments are recorded. Based on conversations with many other researchers and the teamÂs own investigation, tape switches were ultimately determined to be the most appropriate device for the speed data collection. Tape switches can achieve the appropriate accuracy desired and have fairly simple set-up and data post processing compared to the other methods. The following sections summarize each of the data collection devices and the reasoning behind choosing tape switches for collecting data. 3.10.2.1. Hi-Star Traffic Analyzers In the Phase I Interim Report, the research team recommended collecting speed data through the use of traffic classifiers with sensors temporarily placed on the pavement surface. The Nu- Metrics Hi-Star Portable Traffic Analyzer was recommended. This self-contained unit monitors traffic flow conditions by using Vehicle Magnetic Imaging technology to continuously record volume, speed, and vehicle classification data. The benefits of this device are simple equipment installation and user-friendly post processed data that can be easily manipulated. The devices are relatively inconspicuous to drivers, rendering them less likely to influence data integrity. To ensure the Hi-Star Traffic Analyzer met the above criteria, the research team contacted various state agencies, university professors, and equipment vendors to discuss their experience with it. At the request of the research team, Coral Sales Company, a vendor for Hi-Star equipment, conducted a presentation at Kittelson & Associates, Inc. about the equipment capabilities, installation, and accuracy. Coral Sales Company brought samples of the device and output data. From this presentation, the research team determined that this device was not likely to record data with the level of accuracy needed for this research. As stated by Coral Sales Company, each individual device is accurate within 2 to 3 mph; therefore, two devices in series have the potential to be only accurate within 4 to 6 mph. The team also learned that, although it is possible to collect data of individual vehicles, the device and data software is set up to place vehicles in Âspeed bins. Data memory limitations may make it impossible to adequately assess the full range of speeds (say 60 mph to stop) in suitable speed gradations. Collecting speed data of individual vehicles also requires additional post-processing of the data. The research team also contacted professors at the University of Nebraska, Oregon State University, and Pennsylvania State University to discuss their experience with the Hi-Star devices on other research projects. Conversations with these professors confirmed that the accuracy of these devices in series may not be sufficient for this research and that collecting speed data for individual vehicles would require additional efforts. 3.10.2.2. Video Photography Based on the concerns with the accuracy of the Hi-Star devices, the research team also began investigating video photography as a potential data collection methodology. Video photography uses digital video cameras that can record at 30 frames per second. Because of this recording speed and estimated vehicle speeds during data collection, a large speed trap would be required
NCHRP 3-74 Chapter 3 Selection of Speed Reduction Treatments at High-Speed Intersections Testing Plan Kittelson& Associates, Inc. Page 3-35 to achieve an appropriate level of accuracy. For example, measuring vehicle speeds at 60 mph and using a speed trap of 44 feet, the video cameras can only provide accuracy within approximately 4 mph. As the speeds go down, the accuracy increases with the 44-foot trap; however, at slower speeds this distance no longer provides spot speed data. A larger speed trap provides more accuracy at higher speeds; however, the larger trap creates greater time for vehicles to change speeds within the speed trap and no longer provides spot speed data. The appropriate and desired speed trap needed to be calculated for each site and, in some cases, the most desired length of the speed trap may not have been identified until after the speed data was collected. Video photography requires extensive post-processing that can induce error due to the subjectivity of the data recording. Video photography requires a post-processor to identify the point at which a vehicle passes a line on the pavement. In some cases, the video frame could show the front of the tire passing the roadway mark. In other cases, the video frame could show the middle of the tire passing the line. Due to the inaccuracy of the video camera, the vehicle could be anywhere from 0 to 3 feet beyond the mark, but still recorded as the beginning of the speed trap. In addition, video detection requires the post-processor to identify vehicles traveling within a platoon by manually measuring gaps in traffic. The visibility of the cameras and researchers also is a concern when using this device. For security reasons, a researcher would have to remain at the site to watch the camera and, due to limited recording time, replace the camera tapes every two hours. This increases the chance of researchers being visible to passing vehicles. At some locations, the scenery would allow cameras to be placed out of view of drivers, such as near a utility pole or tree. However, in some desert or rural areas, cameras would have to be placed in more visible areas such as on a tripod or fence post near the edge of the roadway. 3.10.2.3. Tape Switches and Traffic Classifiers In addition to Hi-Star devices and video photography, tape switches also were investigated. Tape switches include two switch wires spaced 10 feet apart connected to a traffic classifier that records speed data between the wires to the nearest 1/10th mile per hour. Speed data is recorded for individual vehicles, and platooned vehicle data can be removed by evaluating the vehicle headways during post-processing. Data from the traffic classifier can be imported into Excel and post-processed to provide speed profile data. Although this type of device meets the criteria required to collect the appropriate type of data for testing, the research team identified concerns with the tape switches being visible to drivers. This device requires that the tape switches be taped to the pavement with gray tape. Therefore, the potential exists for these tapes to be visible to drivers as they pass over them or to create a slight vibration that drivers might feel when they pass over the tapes. To resolve this concern, the research team contacted various researchers experienced with this type of device. During one of these discussions, a researcher explained that, in a recent study using tape switches, he and the other researchers were not able to see the tape switches when they drove through the study area, even when they knew the locations of each tape switch. Other researchers confirmed that they did not typically have issues with the tapes being visible to drivers and that the visibility of the tape switches depends on the pavement type.
Chapter 3 NCHRP 3-74 Testing Plan Selection of Speed Reduction Treatments at High-Speed Intersections Page 3-36 Kittelson & Associates, Inc. To ensure that the actual traffic classifier on the side of the roadway is not visible to passing drivers, the connected wires have a 30-foot lead to the classifier. This allows the classifiers to be placed out of view. An additional concern about the use of tape switches is the potential for them to break or be torn from the pavement under high-volume traffic conditions, in areas with heavy vehicles, or when left in place for a long period of time. This is particularly prominent when tape switches are placed at an intersection approach where drivers will be braking or stopping on the tape switches. Therefore, to further investigate these data collection devices and the concerns raised by other researchers, the team conducted a pilot study at one of the treatment sites in Clackamas County, Oregon. Based on this pilot study, the research team did not observe any driver impact as a result of the visibility of the tapes switches and had little difficulty with the tape switches being removed from the roadway, even with heavy vehicle volumes. The speed data collected from this pilot study was accurate, precise, time stamped, and able to track the speed profiles of individual vehicles. In summary, Hi-Star devices have accuracy limitations that may exceed what could be subtle speed changes with the proposed treatments. Video photography appears to have accuracy limitations in high-speed locations and could require more extensive and subjective data reduction efforts. Therefore, based on the investigations conducted for the three potential data collection devices and methodologies, tape switches were selected as the most appropriate device to collect speed data. Although some concerns were raised about these devices, the pilot study helped confirm that this device can achieve the appropriate accuracy desired and had fairly simple set-up and data post-processing compared to the other methods. 3.11. DATA COLLECTION For the subject treatment to be effective, it must get the attention of drivers and appropriately reduce speed in time for an emergency stop, if necessary, prior to reaching the intersection. Therefore, speed data collection points on the approach to the intersection were designated based on drivers ability to perceive the intersection and sufficiently decelerate in time for an emergency stop. The proposed field data collection scheme consists of an intersection-approach speed profile based on the four speed collection points noted below. 3.11.1. Advance Speed Location for Control Purposes A valid before-and-after experimental design must include Âcontrol speed data collection to account for extraneous non-treatment effects (e.g., seasonal differences). A speed data collection location placed significantly in advance (e.g., ¼ mile) of the treatment application was proposed for this purpose. Such a location would yield vehicle speeds unaffected by the presence of the intersection. 3.11.2. Intersection Perception/Response Speed Intersection design principles require that the intersection be visible to an approaching driver at a sufficient distance to come to a complete stop, following 2.5 seconds of perception-response time (PRT). Therefore, a data collection point was established at the 2.5-second PRT stopping
NCHRP 3-74 Chapter 3 Selection of Speed Reduction Treatments at High-Speed Intersections Testing Plan Kittelson& Associates, Inc. Page 3-37 distance at the posted speed limit. Assuming that data collection would be conducted during dry pavement conditions, the research team selected applied data collection locations based on an estimated dry pavement friction (e.g., 0.65) stopping requirement to ensure that measured speeds reflected actual perceivable conditions. 3.11.3. Accident Avoidance Speed A driverÂs Âlast chance (or emergency opportunity) to avoid an accident in response to a surprise or unexpected hazard requires an instantaneous perception-reaction-time response (e.g., 1.0 second, followed by skidding to a stop just short of the collision point). For example, assuming a 45-mph approach speed and a dry pavement friction coefficient of 0.65, the advance data collection location is 170 feet from the intersection. Exhibit 3-23 displays the advance distances for the driver perception-response and accident-avoidance data-collection points. Exhibit 3-23 Human-Factors-Based Speed Data Collection Distances Advance of Intersection Operating speed (mph) Speed Data 45 50 55 60 Intersection Perception/Response 269â 312â 357â 405â Accident-avoidance 170â 202â 236â 273â 3.11.4. Intersection Entry Speed The speed at which vehicles enter the intersection was measured in close proximity (e.g., at or near the stop bar) to the intersection. This data collection scheme considered drivers ability to detect the intersection and, if necessary, to stop in time to avoid an unexpected hazard, thereby preventing an accident. A significant advantage of this data collection scheme is the sensitivity of measures of effectiveness to driver responses without confounding effects of differing approach speed limits. That is, the placement of speed collection points is based on available driver information processing time, thus avoiding the potential error effect of shorter driver response time associated with a higher approach speed limit. The sensors were positioned at the same locations before and after the subject treatments were installed to ensure direct comparisons between vehicle speeds at the same locations on the intersection approach. However, in addition to such comparisons between speeds at one location before and after the treatment was installed, speed profiles for individual vehicles were established so that vehicle speeds at any point on the intersection approach could be determined in the before-and-after condition. 3.12. ADDITIONAL DATA COLLECTION In addition to speed data collection, the research team used one or two video cameras at each site during the data collection period. The field of view for each camera was: ⢠Camera 1  at the intersection, directed toward the paved intersection area and the stop line or curb line of the approach being studied.
Chapter 3 NCHRP 3-74 Testing Plan Selection of Speed Reduction Treatments at High-Speed Intersections Page 3-38 Kittelson & Associates, Inc. ⢠Camera 2  upstream of the intersection and directed along the approach being studied. The video recording from Camera 1 was used to observe whether each vehicle made a full stop, a partial stop, or no stop at the intersection. The video recording from Camera 2 documented any undesirable driver behavior such as hard braking near the treatment or encroachment on the shoulder or an adjacent lane to avoid the treatment. 3.12.1. Data Collection Layouts Based on this data collection scheme, the research team prepared treatment layouts for all testing sites. The research team prepared data collection plans for each of the sites, identifying the appropriate locations to collect speed data during Âbefore and Âafter data collection. Based on the number of traffic classifiers available for data collection, the team collected data at eight to ten spot speed locations at a given time. In most cases, the research team collected data at eight points to allow for at least one spare classifier to be available if any of the other devices malfunctioned. At an intersection with treatments on two approaches, data was collected at four points on each approach. Exhibit 3-24 shows a data collection plan developed for the Whiskey Hill Road/Meridian Road site in Clackamas County, Oregon. At the site shown in Exhibit 3-24, the research team designed peripheral transverse pavement markings to be installed on the northbound and eastbound approaches. Four data collection points were identified on each approach: ⢠Advance Speed Control Location. The location of this data collection point was determined based on the location of the treatment farthest from the intersection. At each location, the research team verified that the treatment could not be visible from this data collection point to ensure that speeds at this location were not affected by the presence of the treatment. o Eastbound Direction  1,300 feet from the intersection o Northbound Direction  1,800 feet from the intersection ⢠Intermediate Treatment Location. At least two sets of treatments were installed on a given intersection approach at all transverse pavement marking and rumble strip treatment locations. This data collection point measured the speed of vehicles traveling between the two treatments, showing the effects of the first treatment. o Eastbound and Northbound Directions  600 feet from the intersection ⢠Accident Avoidance Speed. At both approaches in Exhibit 3-24, the speed was Âbasic rule. Therefore, an estimated speed of 55 mph was used to measure the approximate accident avoidance distance of 250 feet.
NCHRP 3-74 Chapter 3 Selection of Speed Reduction Treatments at High-Speed Intersections Testing Plan Kittelson& Associates, Inc. Page 3-39 Exhibit 3-24
Chapter 3 NCHRP 3-74 Testing Plan Selection of Speed Reduction Treatments at High-Speed Intersections Page 3-40 Kittelson & Associates, Inc. Intersection Entry Speed. The research team collected intersection entry speeds 100 feet from the intersection at most locations. o Eastbound Direction  100 feet from the intersection o Northbound Direction  165 feet from the intersection (This distance was extended due to a driveway located approximately 100 feet from the intersection.) The data collection points described above were used at most intersection treatment sites. However, in some cases, the data collection points were altered to accommodate different types of treatments or unique site characteristics. For example, the dynamic warning sign sites did not have an ÂIntermediate Treatment Speed due to there only being one treatment per approach; instead, another data collection point was identified. Exhibits 3-25 to 3-28 show the data collection layouts for the remaining four sites in Oregon and the site in Washington. 3.12.1.1. Pilot Test To test the data collection methodology and equipment prior to the Âbefore testing, the research team conducted a pilot test using tape switches at the Whiskey Hill Road/Meridian Road intersection in Clackamas County, Oregon, during the week of April 17, 2006. The data collection equipment was set up as shown previously in Exhibit 3-24 and speed data were collected from 9 a.m. to 6:30 p.m. The research team that participated in this pilot study included three KAI staff, two MRI staff, and two staff from Quality Counts, LLC (a transportation data collection firm). The intent was to have most of the research team members present at the pilot to learn how to operate the data collection devices, to discuss the data collection plan, and to identify any issues with the proposed testing plan or potential testing sites. In addition to testing the equipment and methodology for data collection, the pilot study also investigated two concerns associated with using tape switches for data collection: (1) visibility to drivers; and (2) tapes being removed from the pavement by trucks. The Âbefore testing conducted during the pilot study confirmed that these issues would not affect the research data collection. The tape switches were inconspicuous to drivers, and were even difficult for the research team to see when driving through the site.
NCHRP 3-74 Chapter 3 Selection of Speed Reduction Treatments at High-Speed Intersections Testing Plan Kittelson& Associates, Inc. Page 3-41 Exhibit 3-25
Chapter 3 NCHRP 3-74 Testing Plan Selection of Speed Reduction Treatments at High-Speed Intersections Page 3-42 Kittelson & Associates, Inc. Exhibit 3-26
NCHRP 3-74 Chapter 3 Selection of Speed Reduction Treatments at High-Speed Intersections Testing Plan Kittelson& Associates, Inc. Page 3-43 Exhibit 3-27
Chapter 3 NCHRP 3-74 Testing Plan Selection of Speed Reduction Treatments at High-Speed Intersections Page 3-44 Kittelson & Associates, Inc. Exhibit 3-28
NCHRP 3-74 Chapter 3 Selection of Speed Reduction Treatments at High-Speed Intersections Testing Plan Kittelson& Associates, Inc. Page 3-45 In addition, the team did not have any issues with the tape switches being removed from the pavement during data collection. The tape switches withstood the high percentage of trucks on Meridian Road and Whiskey Hill Road throughout the entire day (a ten-hour period). No switches were damaged, even on the stop-controlled approaches on Meridian Road. As suggested by one of the NCHRP panel members, the research team used a radar gun to check the speed data being collected from the tape switches. Approximately ten speeds were collected on the northbound approach of Meridian Road using the radar gun and were compared with speeds being recorded on the traffic classifiers. The comparison between the two devices resulted in a difference of less than one mile per hour. Therefore, the research team is confident that the tape switches collected accurate data. Clackamas County planned to continue monitoring the effectiveness of the treatments installed during this research project beyond this projectÂs timeline. Based on their experience with other treatments in the county, county staff would like to observe the effectiveness of treatments six months and one year after installation. To allow them to compare this studyÂs data to future data they will collect, county staff installed tube counters for a two-hour period with our tape switches to calibrate the data. Tube counters were installed on the northbound approach of Meridian Road from approximately 10 a.m. to noon during the data collection pilot. The research team provided the county with the data collected from the tape switches to compare the speed data from both devices and develop a calibration that can be used for future speed studies beyond this research project. Speed data collected with the tape switches during this time will not be included in the Âbefore data for this site, to exclude any effects that may have occurred due to the tube counters. In addition to speed data collection, the research team used three video cameras at the site during the data collection period. The field of view for each camera is described below: ⢠Camera 1  at the intersection, directed toward the paved intersection area and the stop line or curb line of the approach being studied. ⢠Cameras 2 and 3  upstream of the intersection and directed along each approach being studied (northbound and eastbound approaches). Overall, the tape switches and video recording provided sufficient data for the pilot test to be used as the Âbefore testing at this site in Clackamas County. 3.13. BEFORE-AND-AFTER TESTING After the pilot testing, the research team conducted the Âbefore testing at all the other candidate sites. The same equipment and methodology described in the pilot test were used at all other sites. Quality Counts (QC) served as the primary staff on-site during all testing. However, the team also ensured that one researcher was on-site during the beginning of each testing period to assist in laying out the data collection points and making decisions if collection points needed to be changed. In most cases, QC and the research team followed the data collection layouts to identify the testing points. However, in some cases, when the team arrived on-site, the points needed to be modified due to existing driveway locations or other complexities not visible on the
Chapter 3 NCHRP 3-74 Testing Plan Selection of Speed Reduction Treatments at High-Speed Intersections Page 3-46 Kittelson & Associates, Inc. aerial schematics. As described previously, after the treatments were installed a three-month acclimation period was used prior to the Âafter testing. In most cases, there was an even longer acclimation period, due to the research testing schedule and weather conditions at some sites. The research team made significant efforts during the Âafter testing to be consistent with the Âbefore testing to ensure that the data from each test could be compared to determine the effectiveness of each treatment. The team permanently marked the data collection points with Âmag nails during the Âbefore testing and used them to identify the exact locations during the Âafter testing. In addition, the team also scheduled the Âafter testing on days and under weather conditions similar to each Âbefore test. Exhibit 3-29 shows the before-and-after testing and treatment installation schedule.
NCHRP 3-74 Chapter 3 Selection of Speed Reduction Treatments at High-Speed Intersections Testing Plan Kittelson& Associates, Inc. Page 3-47 Exhibit 3-29 Treatment Testing and Installation Schedule State/County Agency Site Treatment Before Testing Treatment Installation After Testing 1 Whiskey Hill Road/Meridian Road (south of Aurora, OR) Transverse Pavement Markings April 18, 2006 May 31, 2006 September 26, 2006 2 Canby-Marquam Highway/Lone Elder Road (south of Canby, OR) Transverse Pavement Markings April 27, 2006 May 31, 2006 September 27, 2006 3 Redland Road/Bradley Road (east of Oregon City, OR) Transverse Pavement Markings April 28, 2006 May 31, 2006 September 29, 2006 Clackamas County, OR 4 Redland Road/Ferguson Road (east of Oregon City, OR) Transverse Pavement Markings April 28, 2006 May 31, 2006 September 29, 2006 Oregon DOT 6 OR 6/Wilson River Loop Road (near Tillamook, OR) Transverse Pavement Marking May 4, 2006 May 19, 2006 September 28, 2006 Washington DOT 8 SR 26/SR 24/1st Street (near Othello, WA) Dynamic Warning Sign May 26, 2006 September 1, 2006 March 8, 2007 10 US82 @ SH98 (Bowie County) Dynamic Warning Sign June 13, 2006 August 1, 2006 November 13, 2006 11 US271 @ FM726 (Upshur County) Rumble Strips June 14, 2006 July 26, 2006 November 14, 2006 12 US271 @ FM593 (Upshur County) Rumble Strips June 15, 2006 July 26, 2006 November 15, 2006 Texas DOT 13 US271 @ FM2088 (Upshur County) Rumble Strips June 16, 2006 July 26, 2006 November 16, 2006
