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13 STANDARDS AND GUIDELINES FOR USE A minimum of three lights on both sides of the cross- walk on two-lane roadways; and Given the novelty of IPM system use on public roadways, A minimum of one light per lane on both sides of the little direction in the form of standards or guidelines is avail- crosswalk on roads with more than two lanes; and able to support proper installation, operation, and maintenance · Be installed in the area between the outside edge of the of the systems. At the federal level, the Manual on Uniform crosswalk line and 10 ft from the outside edge of the Traffic Control Devices (MUTCD) (2004) provides standards, crosswalk, facing away from the crosswalk if unidirec- guidance, options, and support for traffic control devices in the tional or away from and across the crosswalk if bidirec- United States. State officials either wholly adopt the standards tional (an optional, additional yellow light indication defined in the MUTCD or develop unique state-level standards. visible to pedestrians in the crosswalk is permitted to Some countries outside of the United States have developed indicate to pedestrians that the in-roadway lights are in- their own IPM system standards and guidelines. deed flashing as they cross the street). Federal Standards and Guidelines Additional guidance provided in this section relates to pedes- trian walking speeds and the subsequent period of IPM system Although the MUTCD provides significant general guidance operation. A normal walking speed of 4 ft per second or less related to traffic control devices (e.g., signs, markings, and should be used, depending on the nature of the pedestrian pop- highway traffic signals), this reference contains few explicit ulation (e.g., a high proportion of elderly or wheelchair-bound standards, guidance, or options for IPM system use. Federal pedestrians suggests a lower walking speed and longer period standards and guidelines for the installation, operation, and of IPM system operation). Furthermore, depending on the maintenance of IPM systems were developed as recently as length of the crosswalk and presence of a median, sufficient 2000, with a focus on pedestrian crosswalk applications. The width for pedestrians to wait and median-mounted pedestrian MUTCD defines "in-roadway lights" as: "A special type of actuators may be required. In addition, Section 4L.02 recom- highway traffic signal installed in the roadway surface to mends installing the IPM system markers in the center of each warn road users that they are approaching a condition on or travel lane out of the normal vehicle tire path. adjacent to the roadway that might not be readily apparent and might require the road users to slow down and/or come For non-crosswalk applications of IPM systems, experi- to a stop" (MUTCD, Section 4A-3, 2004). mental approval may be sought and granted by the FHWA. One benefit of IPM system implementation under FHWA Section 4L.01 Application of In-Roadway Lights of the "experimental" status includes a reduced risk of liability for MUTCD states that "in-roadway lights shall not exceed a the requesting agency (i.e., in the event of deaths, injuries, or height of 0.75 inches above the roadway surface" but pro- property damage, attributable to a nonstandard device or ap- vides more flexibility in flash rates, stating that "the flash rate plication). Additionally, improved evaluation can lead to for in-roadway lights may be different from the flash rate of changes in the MUTCD and widespread benefits to agencies standard beacons" (MUTCD, Section 4L.01, 2004). and motorists. Specific to pedestrian crosswalk applications, "Section Note that Section 4L of the MUTCD classifies IPM sys- 4L.02 In-Roadway Warning Lights at Crosswalks" of the tems as a type of traffic signal rather than a pavement marker, MUTCD contains standards related to the installation and op- delineator, illumination source, etc. This classification is eration of IPM systems. In summary, IPM systems shall likely attributable to the nature of the application considered; at pedestrian crosswalks, IPM systems function to alternately · Be installed only at marked crosswalks with applicable stop or permit traffic to proceed depending on pedestrian warning signs (not at crosswalks controlled by YIELD presence. Similarly, a highway traffic signal alternately stops signs, STOP signs, or traffic control signals); or permits traffic to proceed depending on vehicle or pedes- · Be installed on both sides of the crosswalk, spanning its trian presence. Other types of IPM system applications, such entire length; as horizontal curve or adverse weather warning, multiple-turn · Initiate operation based on pedestrian actuation and lane or tunnel guidance, or vehicle and truck inspection point cease operation at a predetermined time after the pedes- illumination may be more appropriately categorized as pave- trian actuation or, with passive detection, after the ment marking, delineator, or illumination source, respectively. pedestrian clears the crosswalk; In Section 1A.13 of the MUTCD, which provides a broader · Display a flashing yellow signal indication, with a flash definition of terms, IPM systems are explicitly defined as not rate of not less than 50 and not more than 60 flash periods being highway traffic signals. This breadth of IPM system per minute (flash rates between 5 and 30 flashes per sec- application and subsequent function suggests a similar re- ond might induce epileptic seizures and shall not be used); quired breadth in related standards and guidelines. Table 1 · Be installed to meet minimum spacing requirements: summarizes MUTCD chapters or sections that currently pro- A minimum of two lights on the approach side of the vide some related direction or would require future modifi- crosswalk on one-lane, one-way roadways; cation to better address IPM system use.
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14 TABLE 1 APPLICABLE MUTCD STANDARDS AND GUIDANCE Applicable MUTCD Standards and Guidance Warning School zones 7B.11 School Speed Limit Assembly 7C.03 Crosswalk Markings Construction zones 6D.03 Worker Safety Considerations 6F.73 Raised Pavement Markers Highway-rail crossings 8B.06 Turn Restrictions During Preemption 8B.21 Stop Lines 10C.23 Pavement Markings Horizontal curves 3D.02 Delineator Design 3D.03 Delineator Application 5E.03 Edge Line Markings Adverse weather Guidance Multiple-turn lanes 3D.02 Delineator Design 3D.03 Delineator Application Merge locations 3D.02 Delineator Design 3D.03 Delineator Application Tunnels 3D.02 Delineator Design 3D.03 Delineator Application 5E.04 Delineators Regulation Intersection stop bars 8B.21 Stop Lines Left-turn restrictions 8B.06 Turn Restrictions During Preemption Illumination Vehicle/truck inspection points None Environmentally sensitive areas None State-Level Standards and Guidelines termine the appropriateness of IPM systems compared with conventional marking, delineation, and illumination systems. Preceding the standards developed for inclusion in the This guide also includes a detailed example application of MUTCD, Caltrans first issued guidelines and standards for these principles at a horizontal curve section. the installation of IPM systems in 1998, again with a focus on pedestrian crosswalk applications. The development of these standards and guidelines followed several years of IPM system Applications testing and evaluation. Current standards and guidelines have The Dutch suggest that IPM systems are appropriate for use been updated to reflect and reference changes in the MUTCD. in any situation where road user lane-tracking ability could be Example language related to IPM system operation follows: enhanced, and are particularly beneficial at horizontal curves. Flasher units for IRWLs shall be installed in IRWL equipment The Dutch guidelines recognize that because of the inherent enclosures. Flasher units shall indicate when the IRWL is low-light yield capability, IPM systems are not recommended activated. The flash rate shall be between 50 and 60 flashes per for determining the position of the road user in relation to minute. The flash rate and period for the IRWL shall conform with other vehicles, recognizing foreign objects on the road sur- Chapter 4L of the California MUTCD. The flash rate shall conform to the requirements in Section 8.3.3 of the National Electrical face, or recognizing vehicles or people. Manufacturers Association Standards Publications No. TS 1 Traffic Control System. The minimum pedestrian crossing time shall be based on a walking speed of 4 feet per second. Advantages and Disadvantages Advantages of IPM systems, as reported by the Dutch, include International Standards and Guidelines increased traffic safety, increased road user comfort, reduced light pollution and carbon dioxide emissions, the potential One of the more comprehensive guides for IPM system use, for installation in remote areas (not connected to an electrical Recommendation for Use of Active Marking, was published grid) through the use of solar technology, elimination of the by the Province of Noord-Holland in the Netherlands in need for transition segments (low-light output requires no 2005. This guide details: (1) appropriate applications of IPM adaptation time for the road user when changing from illu- systems; (2) the advantages and disadvantages of these sys- minated to nonilluminated segments, or vice versa), reduced tems; (3) various functional and technical requirements in- residual materials at the end of the life cycle as compared cluding light source and housing, light color, light intensity, with conventional lighting, and typically lower costs as com- aperture angles, and placement; and (4) a decision tree to de- pared with conventional lighting.
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15 Disadvantages of IPM systems include the need to close great distance, but not so much light that the driver is unable the road completely during construction or maintenance if to see other road users or obstacles in front of him or her. In the IPM system is installed along the centerline (construction situations where surrounding lighting is present, a higher light or maintenance of conventional lighting systems typically intensity must be used than in situations where it is almost allow one lane to remain open), the loss of IPM system com- completely dark. ponents when the road surface is repaired or removed, and potentially higher costs as compared with conventional light- Aperture angle, defined as the angle indicating the width ing if hardwired IPM systems are installed on multiple lane of a light beam, is an important factor in IPM system appli- roadways (Recommendation . . . 2005). cations along horizontal curves. As the radius tightens, the road user's view through the curve becomes smaller, making it necessary to place more markers in a certain section of the Functional and Technical Requirements road so that the path of the curve becomes recognizable. If the With respect to light sources and housings for IPM systems, radius is small (less than 1,968 ft for one-lane roadways or the Dutch provide the following recommendations (Recom- greater than 3,281 ft for two-lane roadways), it is also neces- mendation . . . 2005): sary to direct the markers at the oncoming traffic (an alternative is to increase the aperture angle, but this compromises the · Light sources should have a lifespan equaling at least light yield). The Dutch recommend using a 12-degree hori- that of conventional pavement marking equipment, and zontal aperture angle and a 10-degree (minimum 8-degree, preferably that of road surfaces; "only LED technology maximum 12-degree) vertical aperture angle for optimal vis- currently meets this criteria." ibility over the complete IPM system-equipped curve section. · The protective housing should be composed of high- quality synthetic material, which can be milled out at the When placing the IPM system markers in the pavement, the end of its lifespan or with replacement of the asphalt; the Dutch define two maximum height requirement conditions. supplier must demonstrate that the housing has a dura- The maximum height over the road surface is 0.20 in. for hori- bility lasting at least 20 years. zontal curves with mixed traffic (i.e., cars, mopeds, and motor- · After installation, a malfunctioning light source should cycles) and 0.39 in. for horizontal curves with car traffic only. be replaced easily, without drilling or milling. The light source's sensitivity for pollution from its surroundings When positioning IPM systems on the pavement surface, must be minimal; the absence of sharp joints and edges markers are always installed along the outside edgeline of prevents the gathering of dirt and dust and increases the one-way roadways, regardless of the number of lanes. For self-cleaning effect of rain or tire traffic. two-way roadways, the markers are placed along the center- · Supply and mounting of light source(s), electronic parts, line of the roadway. The Dutch recommend placing the IPM and housings as separate components ease replacement system markers directly on (or in) the existing passive mark- when a failure occurs, reduces waste, and provides the ing or immediately beside it to maintain the delineation of the potential to reuse parts that have a longer lifespan than roadway (Recommendation . . . 2005). the road surface. The marker spacing is the most important variable factor With respect to light color, the Dutch require the color of the when implementing an IPM system. The desirable distance IPM system marker to be the same as that of the existing between markers is affected by the visibility of the locale, the (passive) marking. radius of the roadway, and the maximum travel speed. On a straight road section the maximum speed limit is the only The desired light intensity depends on where the IPM factor that determines the distance between the markers. The system is used and is influenced by the maximum road user Dutch recommend various speed-based marker distances perception distance (with an assumed preview of 15 s) and ranging from approximately 82 ft at 20 mph to approximately the presence and intensity of the surrounding lighting. The 325 ft at 75 mph. Dutch recommend the following light intensities based on surrounding lighting conditions: To determine appropriate marker spacing along a hori- zontal curve, the Dutch provide the following relationship: · 500 millicandelas in complete darkness or with low dif- ( R + 0.5 * B) ( R - 0.5 * B - S ) fused lighting; KL = * arccos · 1000 millicandelas when background lighting is present; N ( R + 0.5 * B) and where: · 2000 millicandelas when combined with or near conven- tional lighting. KL is the marker distance in radians, R is the radius of the curve measured to the centerline of The light yield from an IPM system can be relatively low. the lane curve in meters, Enough light must be emitted to make the marker visible at a B is the width of the lane in meters,