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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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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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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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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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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).
