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26 In Japan, Munehiro et al. (2006) examined the required overheating, and subsequent failure. Street sweepers also luminous intensity of IPM systems in fog conditions. They cause debris build-up; the units must be periodically cleaned evaluated LED marker characteristics during day and night (approximately once per month) to function properly. System conditions, asking 20 subjects to subjectively evaluate glare, costs were not available for this location. visibility, and safety of test deployments of varying LED in- tensities. They found that the desired luminous intensities of No formal evaluations have been performed to determine 1000 candelas (cd) for daytime and 70 cd for nighttime were the effectiveness of this IPM system, but a representative from acceptable for IPM systems during fog conditions. SCDOT notes that favorable comments regarding the system were received from the public following implementation. In a related study, Hagiwara et al. (2001) investigated the luminous intensity of LEDs in snow conditions and reported difficulty in relying on illuminated markers for tracking dur- Various Locations, State of Virginia ing snowstorms, particularly during daylight snowstorm con- ditions. Markers would have to be spaced closely to contrast Sections of I-64 and I-77 in Virginia are prone to heavy fog. with the background light levels and the increased scatter of An early IPM system, on a 5.8-mile segment of I-64, was light during these events. implemented in 1976, and continually operated until 1997, when the system was upgraded. Upgrades included brighter Domestically, Whitlock and Weinberger (1998) noted that edgeline markers (previously, incandescent lights were used), flashing amber lights significantly enhance driver awareness new visibility sensors, and 10 DMSs. during adverse weather conditions for IPM systems imple- mented at pedestrian crosswalks (1998). A before-and-after evaluation of the 1976 IPM system on I-64 showed a decrease in crashes from 40 (four fog-related) Practical experience related to IPM system effectiveness to 31 crashes (one fog-related) in a 19-month period. After during adverse weather is described here. the system upgrades in 1997, another 19-month before-and- after study examined crash rates. Again, a decrease in crashes was observed, from 60 (five fog-related) to 54 crashes (two fog-related) (Lynn et al. 2002). The statistical significance of I-526, Cooper River Bridge, Charleston, these observed changes was not reported. South Carolina In 1992, the SCDOT installed an IPM system on the Cooper Most recently, the Virginia Transportation Research River Bridge as a result of a review of environmental im- Council (VTRC) has proposed using several different sys- pacts potentially caused by fog created by a nearby paper tems, including IPM systems with chase sequence capabili- mill (Potash and Brown 1988). The IPM system, intended to ties to reflect variable speed limits, to help prevent crashes in provide longer-range delineation of the road beyond the fog-prone areas. In February 2007, the Virginia legislature range of vehicle headlights, was just one of five measures enabled this application by passing legislation that allows use selected for implementation. Other measures include dy- of variable speed limits. The VTRC also recommends inves- namic message signs, closed-circuit television cameras, tigation of IPM system effectiveness for pacing vehicles in environmental sensors, and a control and communications fog and warning road users of tailgating vehicles (S. Shergold, infrastructure (Goodwin 2003). personal communication, July 26, 2007). An IPM system originally designed for airport runway GUIDANCE lighting was used. System markers are placed every 110 ft along the edgelines of the bridge. The IPM system is manu- With the primary intent to guide road users, IPM systems ally activated by a remote traffic management center (TMC). have been implemented at multiple-turn lanes, merge loca- Weather sensors located on the bridge alert the TMC when fog tions, and tunnels. conditions exist. The TMC verifies the condition by camera or with an on-site inspection. When visibility conditions reach The general effectiveness of IPM systems in enhancing less than 750 ft, the edgeline markers are illuminated. The road user guidance was investigated by Styles (2004b). Lat- markers are operated in a steady-burn state (R. Clark, personal eral placement, speed, brake use, high-beam headlight use, communication, Aug. 13, 2007). In light fog, every other and travel on (or over) the centerline were considered for a marker is illuminated (i.e., a marker spacing of 220 ft); in heavy two-lane roadway in Australia. Styles observed that driver fog, all markers are illuminated (i.e., marker spacing of 110 ft). distance from the centerline increased significantly (+2.44 in. and +3.07 in.) at two of four test locations. Travel farther Frequent light source failures have proven challenging and from the centerline increases the distance between oncoming costly for this system. Additionally, the slope of the bridge vehicles and was surmised to lead to fewer head-on colli- results in sand and other sediment build-up on the markers sions. At the other two test locations, the distance to the cen- (on the downslope), leading to reduced luminous intensity, terline decreased (-1.99 in. and -2.46 in.), but only the latter
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27 decrease was statistically significant at the 90% confidence system operates 24 hours per day (G. Tsutsumi, personal com- level. Researchers concluded that the clearer delineation of munication, July 2007). The system was originally test oper- the centerline may make road users more comfortable travel- ated in two different modes: (1) steady-burn, and (2) forward ing closer to the centerline, in contrast to traveling closer to chasing. The forward chase sequence was perceived to be what may be a more poorly delineated roadway edge. The more effective in keeping traffic moving and, hence, is the study further concluded that brake use and high-beam head- only mode of operation used currently. light use were not significantly affected owing to the IPM system, but some reduction in speed (ranging from -0.75 to Frequent LED failures, likely resulting from intersec- -1.93 mph) was observed in a before-and-after review of the tion traffic under normal operation and particularly from IPM system installation. vibrations produced by heavy trucks, occur about once every two to three months. The manufacturer is working with the city to minimize these failures. No real-time, re- Multiple-Turn Lanes mote failure feedback is available for this system. Failures are noted from field observation, from remote visual inspec- IPM systems have the potential to enhance lane-tracking dur- tion using nearby closed-circuit cameras, or through public ing multiple-turn-lane maneuvers and subsequently reduce feedback. the occurrence of sideswipe crashes. The initial installation of the IPM system was reported to SH 99 at Arch Road, Single-Point Urban cost approximately $75,000, with annual maintenance costs Interchange, Stockton, California of approximately $15,000 per year. The maintenance costs are primarily attributable to the frequent LED failures. Addi- In Stockton, California, an IPM system was implemented to tionally, large sections of the intersection must be closed to enhance two-lane, left-turn operations from all approaches of service the system. the Arch Road at State Highway 99 (SH 99) intersection (see Figure 18). This intersection is a single-point urban inter- No formal evaluation has been conducted to determine the change with average daily traffic of 14,000 vehicles. effectiveness of the IPM system in improving road user guid- ance through this intersection. The city of Stockton has, how- The IPM system consists of white LED markers mounted ever, received positive public feedback regarding the IPM flush with the pavement surface. The system is hardwired for system. both communications and power, both of which run in an underground conduit. Each marker is individually spliced to the power source to provide easy access for replacement. Wabash Avenue at Veterans Parkway, Springfield, Illinois The IPM system is activated during the left-turn phase of In 2004, the Illinois DOT (IDOT) installed an IPM system at the traffic signal. The markers define the lane line of the two the intersection of Wabash Avenue at Veterans Parkway in left-turn lanes and illuminate in a forward chase sequence, Springfield, Illinois (see Figure 19). The IPM system was in- giving road users a sense of motion and providing positive tended to provide a more permanent means to delineate the directional guidance. The markers remain illuminated until the entire curve is lit; the chase sequence then repeats. The FIGURE 18 Multiple-turn lane IPM system application, FIGURE 19 Multiple-turn lane IPM system application, Stockton, California (Courtesy: Caltrans). Springfield, Illinois (Courtesy: SmartStud Systems).
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28 lanes at this busy intersection, compared with dashed pave- ment markings that fade within a matter of months. Left-turn delineation for dual left-turn lanes is provided at all approaches. When the left-turn phase is activated, the white LED markers illuminate and operate in a steady burn through the turn phase and approximately three to four seconds after the phase. Marker visibility is described as acceptable during daylight, but superior at night. The system operates 24 h a day. Similar to experiences in Stockton, California, the primary issues with this IPM system have included LED failure. Two full replacements of markers (but not cabling) have occurred since the initial installation owing to the large number of LED failures. Although the system was under war- ranty and replacement costs were assumed by the manufac- turer, IDOT still had to provide costly and disruptive traffic control through the intersection (K. Armstrong, personal com- FIGURE 20 Merge location IPM system application, Wayne Township, New Jersey (Courtesy: HIL-Tech, Ltd.). munication, Aug. 16, 2007). The entire cost for this system, including traffic control, was approximately $120,000. According to IDOT, the IPM system has improved traffic control at the intersection by better delineating the dual left-turn lanes at each approach. This effect has not been confirmed through formal evaluation, however. Significant positive feed- back, including several favorable editorials published in local newspapers, was received after the installation of the system. Merge Locations At merge locations, IPM systems have the potential to enhance lane-tracking for road users, particularly if the merge maneu- ver is complicated by curvilinear roadway geometrics. Route 46, Totowa Burrow, Wayne Township, FIGURE 21 Merge location IPM system application (arrow view), New Jersey Wayne Township, New Jersey (Courtesy: HIL-Tech, Ltd.). In 2006, the New Jersey DOT (NJDOT) installed an IPM sys- tem on Route 46, in Totowa Burrow, Wayne Township, New Jersey (see Figures 2022). This IPM system was intended to assist road users with lane delineation at an entry ramp merge location within a curve. System markers were used to delineate centerlines and edgelines and to depict an arrow on the pavement at the merge location. The IPM system oper- ates in a steady-burn state 24 hours per day. The lights are visible during daylight hours and dimmed at night. Installation issues have challenged the effective operation of this IPM system. The general roadway contractor was not familiar with either the IPM product or installation proce- dures. Channels to house the cables connecting the markers were not placed deep enough into the pavement, eventually exposing the cables to traffic and the environment. This led to early cable fatigue and failure and subsequent whole sys- tem failures. Challenges also existed related to the design of FIGURE 22 Merge location IPM system application (taper view), the "merge" arrow as road users had difficulty determining Wayne Township, New Jersey (Courtesy: HIL-Tech, Ltd.).
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29 that the lighted object is an arrow until he or she is immedi- tions, the IPM system could provide escape or evacuation ately in proximity to the arrow. route delineation regardless of the direction of traffic. Despite these installation challenges, NJDOT personnel Domestically, IPM systems have been recently imple- consider the IPM system to be very effective and recom- mented in tunnels in the states of California, Hawaii, and mended its use in fog-prone areas or other locations needing Washington. additional roadway delineation. IPM systems were only rec- ommended for the most critical locations, however, because of the system cost. Specific IPM system costs were not read- McClure Tunnel, Santa Monica, California ily available from NJDOT; system installation was included In October 2003, an IPM system was installed in the McClure as a construction change order on a larger project. Tunnel, where I-10 meets the Pacific Coast Highway in Santa Monica, California. The IPM was installed on the center Tunnels median barrier to delineate the center of the tunnel and guide road users through a sharp curve (see Figure 23). IPM systems used in tunnels can provide guidance and addi- tional roadway illumination for road users. Such systems The tunnel environment limits opportunities for self- have been shown to be more effective at night; the tunnel cleaning of IPM units (i.e., through rainfall); however, the environment is similar to night conditions. IPM systems can barrier mount also limits dirt and debris build-up on the IPM be particularly beneficial when a road user enters a dark system markers. Caltrans personnel report infrequent main- tunnel from a fully lit daytime environment. tenance activity, resulting only when vehicles hit the center median barrier and dislodge the IPM system electrical wires These IPM systems have been used extensively in European or conduit. The IPM system cost was reported to be between tunnels and their effectiveness in improving safety and oper- $60,000 and $70,000; the length of the tunnel and the dis- ation has been the subject of much study. tance between markers was not reported. Caltrans personnel purport enhanced visibility for road The average travel speed through tunnels has been shown users and a reduction in crashes as a result of the IPM system, to increase slightly, whereas speed limit violations decreased but a formal evaluation has not been done to support these following implementation of IPM systems (Eigentler 2005). findings (G. Toor, personal communication, July 27, 2007). One explanation for the increased average speed is that road users may feel more comfortable driving in the tunnel. Addi- tionally, road users more commonly maintained a two-second Wilson Tunnel, Route 63 (Likelike Highway), or more headway distance in higher-density traffic following Honolulu, Hawaii implementation of IPM systems. In May 2006, the Hawaii DOT (HDOT) implemented an Another study conducted by Ruhr University in Bochum IPM system in the eastbound Wilson Tunnel on Route 63 examined the use of IPM systems in three different tunnels in outside of Honolulu (see Figures 24 and 25). The intention of Germany (Eigentler 2005). The study measured speed through the tunnel and distances maintained from the side of the tun- nel. In addition, road users were surveyed after they exited the tunnel. Trucks changed their lane-tracking to travel in the rightmost portion of the lane following IPM system imple- mentation. A small increase in average speed, leading to a smoother speed progression through the tunnel, was also ob- served. Road users were better able to adjust from the open road environment to the tunnel environment without slowing down. This is an operational advantage in that decreases in speed at the tunnel entrance can cause a sufficient disruption in the traffic flow, leading to major congestion in heavy traffic. Austria was the first country to approve guidelines for IPM system use in tunnel applications in its Guidelines for Tunnel Equipment (Eigentler 2005). After a 1999 fire disaster, the Tauern Tunnel reopened with an IPM system to help guide road users through the tunnel. In Norway, fire agencies are pro- FIGURE 23 Tunnel IPM system application, Santa Monica, moting use of IPM systems in tunnels; in emergency situa- California (Courtesy: SmartStud Systems).
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30 crews or through public notifications. The initial cost of the system was $70,000, which is comparable to the system costs reported for the Santa Monica, California, IPM system tunnel application. Although no formal evaluation of effectiveness has been performed, HDOT reported a perceived improvement in tunnel operation and safety as a result of the IPM system. Tunnel # 1, SR-20 between Newhalem and Diablo, Washington In July 2005, the Washington State DOT (WSDOT) imple- mented an IPM system in Tunnel #1 on State Route 20, be- tween Newhalem and Diablo (see Figure 26). The IPM system implementation was motivated by a desire for increased safety through added delineation inside the tunnel, particularly FIGURE 24 Wilson Tunnel (inside the tunnel), Route 63, for road users crossing from bright daylight conditions into Honolulu, Hawaii (Courtesy: Hawaii DOT). the dark tunnel. the IPM system was to provide lane guidance and reduce At this location, the roadway has two lanes (one lane in crashes; the system provides a guidance and warning function each direction) and a width of 30 ft (including shoulders) inside both inside the tunnel and outside at the tunnel exit. the tunnel. The tunnel is 630 ft in length. The average daily traffic for both directions of travel through the tunnel is 1,500 The subject roadway consists of two one-way tunnels, each vehicles per day, and the posted speed limit is 45 mph. with two 12-ft lanes and sidewalks. The length of each tunnel is approximately 2,700 ft. The average daily traffic for both The IPM system markers are placed along the centerline directions in the tunnel is 29,500 vehicles, with a posted speed for the length of the tunnel. The yellow LED markers operate limit of 35 mph (A. Takeshita, personal communication, in a steady-burn state when activated either by vehicle loop Aug. 1315, 2007). detectors at each tunnel approach or by push buttons for bi- cyclists entering the tunnel. Installation required a saw cut IPM markers are mounted within the double-white center into the concrete for the inductive power line. In addition, a lane lines and on the right edgeline in the eastbound tunnel 6- to 10-in.-wide strip of pavement surface was milled down only. The white LED markers are operated in a steady-burn for a length of about 18 in. in front of and behind each marker state 24 hours per day. (see Figure 27) allowing the marker to be recessed from the traffic lane surface to help avoid damage from snowplows. To date, there have been no reported failures with the mark- ers or system. Failure detection does not occur automatically, Some maintenance is required to clean the individual but is detected through inspection by the HDOT maintenance markers every three to six months as debris and dirt on the FIGURE 25 Wilson Tunnel (exit from the tunnel), Route 63, FIGURE 26 Tunnel IPM system application, between Honolulu, Hawaii (Courtesy: Hawaii DOT). Newhalem and Diablo, Washington (Courtesy: WSDOT).