Chapter 15 – Detection
Page 3 of 3
15.2.11 Emerging Trends
A number of trends in technology and application are emerging in the
Nation. Some of the traffic sensors noted earlier in this Chapter are
gaining more and more application. These include the passive acoustic
array, ultrasonic, passive infrared, and the combination sensors. Others
technologies and applications show promising results for future implementation.
188.8.131.52 Probe Surveillance
As discussed in Chapter
13 on Traveler Information, it is envisioned that the Integrated Network
of Transportation Information (INTI) will not be heavily infrastructure-based;
rather, the long-term path is heavily vehicle-based (but not exclusively)
for the collection of information. This will require widespread utilization
of vehicle probes using GPS and/or cellular phone triangulation, with
the result that the standard design considerations of point detection
and element spacing along the roadway infrastructure may no longer be
applicable. (Note – Probe surveillance using electronic toll tags is not
a "cutting edge" technology. In fact, in terms of infrastructure requirements,
it is very similar to other "point detection" technologies in that AVI
readers are required at selected intervals along the highway to read the
184.108.40.206 Remote Sensing
Aerial surveillance has long been used to monitor the operation of the
surface transportation network. "Observers" in aircraft (fixed wing or
helicopters) fly over the freeway and monitor the conditions in real-time,
using two-way radios to communicate with the traffic operations center
or with service patrols on the freeway. This approach can be relatively
expensive when one considers the expense of leasing or operating an aircraft;
although it does have the benefit of being able to cover a large area.
An emerging trend is the use of remote sensing via unmanned
aerial vehicles, similar to airborne platforms / drones used by the military,
and satellites. Information gathered from satellite, aircraft, and unmanned
aerial vehicles can be used to estimate arterial and freeway traffic characteristics
over long time scales and large geographic areas, including those where
data were previously unavailable. The spatial coverage provided from air-
and satellite-based sensors can potentially support the development of
new metrics that better represent highway utilization and congestion.
Florida DOT is currently experimenting with an unmanned airborne platform
that can be programmed to fly a prescribe route and transmit real time
video images to a TMC. Other possibilities include the integration of
digital video, global positioning systems (GPS) and automated image processing
to improve the accuracy and cost-effectiveness of data collection and
reduction. A number of experiments have been used to estimate vehicle
speeds directly from video images in near real-time by using image registration
and edge detection technologies. Similar techniques have been used to
derive other traffic characteristics, such as, densities, travel times,
delays, turning counts, queue lengths, and platoon dispersion. (15)
220.127.116.11 Networked Video
As technology expands, and the security of the Internet improves, users
are looking at cheaper means to distribute video to a wider audience.
This audience includes operators, response personnel, emergency service
providers and the public. Using the Internet as the communications infrastructure,
live streaming video for a wide variety of applications can be distributed
to numerous users. With this technology, transportation industry users
can utilize their existing CCTV systems to:
- Monitor and respond quickly to incidents
- Monitor critical infrastructure for security purposes
- Archive video for later review for special projects, traffic flow
studies, and construction monitoring
- Provide remote access to video for related uses in law enforcement
and emergency response
- Create public goodwill by providing video feeds to commuters and media
This capability is available to any user with a standard Internet browser.
With excellent bandwidth management, providers can allow hundreds of users
to monitor images and provide users with pan, tilt and zoom capability.
18.104.22.168 Maintenance Decision Support System
FHWA is supporting the development of the next generation of road weather
information systems called the Maintenance Decision Support system (MDSS)
for winter road maintenance decision makers. The program is designed to
respond to changing weather conditions and their impacts on the highway
system. It was designed with the needs of state Departments of Transportation
in mind, and allows winter maintenance managers to:
- View predicted weather conditions throughout the state
- Become aware of the potential for deteriorating road conditions before
- Predict impacts of weather on road conditions
- Plan treatment scenarios based on available resources
- Receive treatment recommendations based on proven rules of practice
The primary goal of MDSS is to get proper weather, road condition, and
resource information into the appropriate people's hands so that they
can make proactive decisions to manage the transportation system before
and during adverse weather conditions.
As noted in Chapter 12,
another emerging trend is the development and deployment sensor technologies
in support of Homeland security – such as devices that automatically and
immediately detect potential threats (e.g., stopped vehicles) along the
roadways and near transportation centers, and commercial vehicle technology
for sensing and identifying hazardous materials.
Another emerging trend is the concept of a national "Infostructure".
The document entitled "Operating the Highway System for Safety, Reliability
and Security; TEA-21 Reauthorization Proposal" (3)
includes the following statement: "To provide timely, comprehensive information
to managers and users of highway-based transportation systems, a program
to implement and operate an information infrastructure or 'infostructure'
of traffic and infrastructure monitoring and data sharing is proposed."
As discussed herein, the need for an Infostructure (and the associated
real time information) exists, as does the technical means to collect
and process the associated information. What is missing is the actual
deployment. The level of surveillance information currently available
is relatively limited. For example:
- Less that 25 percent of the urban freeways in our largest cities are
instrumented for traffic surveillance. Moreover, given the current rate
of deployment (Figure 15-14),
it will be some time before an adequate portion of the freeways in the
largest urban areas are instrumented for collecting the information
so as to enable truly effective operations and management.
Figure 15-14: Projected Growth in Freeway Surveillance D
- Arterial surveillance is virtually non-existent, mostly involving
simple vehicle presence detection for signal control
- Only 25 transit agencies in our 78 largest cities have automatic vehicle
location systems on their fixed route buses, and15 percent of all fatal
crashes occur during adverse weather conditions, yet road weather data
collection stations exist at an average spacing of over 130 miles on
the National Highway System.
Moreover, as discussed in Chapter
12, a related issue (and a relatively new concern) is that of homeland
security. The ability of the surface transportation network to cope with
such contingencies requires additional information and operational capabilities
– for example, to identify potential dangers (and then respond) before
anything can happen, to detect any such catastrophic incidents, to facilitate
first responder access and military deployments, and to effectively route
evacuations from major metropolitan areas.
These facts provide compelling evidence that incentives and / or new
approaches are required to accelerate the development and deployment of
an information infrastructure. The FHWA has recognized this need, sponsoring
several efforts to define an initial vision for this Infostructure. Additionally,
per the aforementioned paper summarizing reauthorization issues, the "ITS
information infrastructure" is identified as "one of the four significant
areas of change that are necessary to achieve an adequate emphasis on
operations in Federal surface transportation programs.
An initial vision and concept for the Infostructure – a "strawman" view
of sorts – has already been developed and documented (12).
As currently envisioned, the Infostructure program "would support both
national and State/local interests. The national program element would
- Statewide (and regionwide) reporting of capacity reducing events on
the National Highway System (e.g. crashes, work zones, road weather
events) using a consistent reporting format, such as is already being
done in the I-95 Corridor Coalition, Arizona, Utah, and a few other
- System performance and weather monitoring of freeways, key arterials
(including evacuation routes), and transit systems in large metropolitan
areas (those with populations exceeding 1 million). This could be accomplished
through deployment of electronic monitoring infrastructure, acquisition
of data from private sector sources, or a combination of these approaches.
- Monitoring of critical transportation infrastructure (e.g. bridges,
tunnels, military routes) for security purposes.
- The State/local element of the program would be focused on producing
information for locally determined security, safety and reliability
purposes, in order to support traffic management, traveler information,
transit management, CVISN (Commercial Vehicle Information Systems and
Networks), emergency management, E-911, and security activities and
The next step in the process leading to ultimately deploying the Infostructure
is the development of a Concept of Operations, which is currently underway
at the time of writing this Handbook. Some of the issues to be addressed
by the Infostructure Con Ops include the following:
- Highway Classifications & Differentiators: Different
types of highways have different operational characteristics. In addition
to freeway, arterial, and bridge / tunnel classification, additional
differentiators, such as freight routes, evacuation routes, military
deployment routes, and routes significantly impacted by snow and other
weather conditions, may also impact the type, amount, and accuracy of
information required for operations.
- Types of Information: Roadway traffic flow information
– such as volumes, speeds, travel times, etc. – are obvious information
requirements for operating the surface transportation network. Other
conditions and functions can affect the information requirements, including:
- Incidents and Video Surveillance – Incidents
reduce the capacity of the roadway and can cause the flow to suddenly
breakdown. Moreover, there are other concerns associated with incidents
beyond their impact on traffic control, including life safety (e.g.,
getting medical treatment to injured parties as soon as possible)
and environmental (e.g., containing and cleaning up any spills of
hazardous materials). Video surveillance has proven very useful
for incident verification and "diagnosis".
- Inclement Weather – Capacity and operating conditions
may also be affected by inclement weather, requiring information
on atmospheric and road surface conditions. This information is
also often required to manage winter maintenance activities. The
initial Infostructure concept envisions a nationwide "grid" of environmental
sensor stations for the purpose of meso-forecasting. The basic information
would include atmospheric temperature, humidity, wind speed / direction,
and precipitation. Additional information and closer spacing of
information collection points (relative to the national grid) may
be required depending on a number of factors, including average
annual snowfall, level of snow maintenance activities (e.g., anti-icing
vs. plowing only), terrain and grades, and spot problems (e.g.,
fog, high winds, frequent icing). (Note: To date, state transportation
agencies have installed over 1,800 ESS nationwide. However, these
sensor stations do not provide adequate geographic coverage (e.g.,
all major road segments) to develop weather information products
at the required temporal and spatial resolutions.)
- Transit – An important element of the nation's
highway network is the transit buses that utilize the roadways.
In addition to monitoring the real-time operations of the roadways,
surveillance of the buses themselves (e.g., location, schedule adherence)
was also identified as a potential information requirement.
- Security – The horrific events of September 11,
2001 demonstrated the need for information that would help protect
critical infrastructure elements, including major highways, bridges,
tunnels, and transit systems. Damage or destruction of a major tunnel,
bridge or transit facility could cause significant injuries and
fatalities, as well as disrupt the transportation system for an
extended period of time. Accordingly, the initial Infostructure
vision includes surveillance subsystems to monitor critical infrastructure,
major transit facilities, military routes, and freight intermodal
connectors and terminals to detect problems quickly and reliably
and to facilitate rapid evacuation and emergency response if needed.
- Information Integration – In addition to collecting
this information, it was determined that the Infostructure should also
include some form of statewide and regional integration supporting the
exchange and sharing of this information between multiple locations
and transportation management centers. This included Statewide reporting
of capacity reducing events on the National Highway System (e.g. crashes,
work zones, road weather events) using a consistent reporting format.
- Local and National Needs – The Infostructure concept
currently envisions supporting both national and State/local interests.
The national elements could include the information (and at a level
of detail) required to support regional / national travel and to manage
major incidents and emergencies – for example: travel time information
on freeways and key "interstate" arterial-type highways; weather information;
statewide reporting of major capacity reducing events (e.g. crashes,
work zones, road conditions); and monitoring of the STRAHNET, emergency
evacuation routes, and critical transportation infrastructure. The local
element of the program could be focused on producing information for
locally determined security, safety and mobility purposes, such as travel
time information on "local" arterials, volume information (for input
to planning / simulation models), CCTV surveillance, and transit system
performance. The distinctions between "national" and "local" may be
significant, particularly if they affect funding mechanisms and the
respective roles of USDOT, State and local agencies, and the private
- Federal, Public and Private Roles – It is currently
envisioned that the Infostructure will not be Federally
mandated (in whole) or Federal controlled. Rather, USDOT may provide
incentives, and will likely play an oversight and coordination role.
The exact nature of the federal role still needs to be addressed, as
well as the roles and relationships between the public and private sectors
in deploying, operating and maintaining the Infostructure.
At the time of preparation of this Handbook, a "Surface Transportation
Security and Reliability Information System Model Deployment" (MDI) was
just beginning in the Orlando, FL vicinity.
15.3 Implementation and Operational Considerations
The surveillance subsystem and the information it collects supports the
other functions of a freeway management program. The process to select
and implement the surveillance subsystem should therefore be based on
the information needs of these freeway management functions. Some steps
in this process are summarized below.
15.3.1 ESS and RWIS Deployment
Reference 25 ("Best Practices
for Road Weather Management") provides the following overview of issues
related to ESS and RWIS deployment. "Several issues must be considered
when planning to deploy ESS and implement RWIS. Concerns include procurement
and maintenance, data sharing, and institutional issues. Partnerships
with neighboring public agencies and the private sector can facilitate
data sharing and help defray the initial and recurring costs of field
sensors, communications infrastructure, central hardware, and processing
software. Another alternative is to fund RWIS component installation as
part of larger construction or Intelligent Transportation Systems (ITS)
projects. Preventive maintenance funds must also be secured to ensure
that sensors are properly calibrated and provide accurate data.
Exchanging environmental data and information with other agencies can
minimize surveillance costs. Environmental monitoring networks can be
created to collect and integrate data from many sources, store relevant
data in centralized databases, and disseminate information in useful formats.
Potential data sources include surface weather observation systems deployed
by the NWS, the Federal Aviation Administration, the U.S. Geological Survey,
the Department of Agriculture, the Forest Service, and the Environmental
Protection Agency. The need for redundant infrastructure can be eliminated
by coordinating with other agencies.
Another major institutional issue is system acceptance. Potential benefits
from ESS and RWIS deployments will not be realized if transportation managers
do not use them. The organizational culture, decision-making processes,
and technical capabilities of users must be carefully considered during
design and implementation. All users desire 'timely, relevant, accurate'
road weather information. However, these criteria may be defined differently
depending on the operational application. For example, a maintenance manager
may consider a 24-hour precipitation forecast 'timely' for treatment strategy
planning, while a traffic manager needs real-time snow accumulation data
to adjust traffic signal timing parameters. 'Relevant' environmental data
is presented to the user in a format that is easily interpreted and suitable
for decision support. Software programs must be developed to customize
raw data (such as soil temperature) into useful information (such as a
pavement temperature forecast based upon air and soil temperatures). Managers
have various technological options depending on their weather information
needs, operational procedures, and mitigation strategies."
15.4.1 TRANSMIT-TRANSCOM System for Managing Incidents and Traffic
TRANSCOM's System for Managing Incidents and Traffic, known as TRANSMIT,
was initiated to establish the feasibility of using Automatic Vehicle
Identification (AVI) equipment for traffic management and surveillance
applications. AVI technology systems are typically installed at toll booths
where they classify oncoming vehicles, then identify them and collect
the toll by reading data stored on a vehicle-mounted transponder through
wireless communication with a roadside antenna. In the New York City Metropolitan
Area, this application of electronic toll collection is called E-ZPassSM.
The current system includes AVI transponder readers installed overhead
at approximately 2.4-kilometer (1.5 mile) intervals in both directions
of the roadway. The spacing between readers was selected to maximize the
probability of incident detection by minimizing the false alarm rate (maximum
of 2 percent) and the mean time to detect an incident (maximum of 5 minutes).
Twenty-two locations were included in the project with a total of 65 antennas.
When a vehicle with the tag passes an antenna, a signal is sent to the
roadside equipment and then it is sent by modem over leased telephone
lines (along with date and time) to a central site at TRANSCOM headquarters
in Jersey City, NJ. The vehicle tag is scrambled to make sure that the
vehicle privacy is assured. The data is then processed in the TRANSCOM
Operations Information Center (OIC) to derive travel time and to detect
incidents. The processed information is sent to similar workstations located
at the Tarrytown, NY Office of the NYSTA, and to the New Jersey Highway
Authority (NJHA) headquarters in Woodbridge, NJ.
AVI data may be used for producing incident alarms. There is a distinct
advantage to the use of toll tags because of their inherent ability to
identify and track individual vehicles, a capability that may only be
approximated with the use of a loop detector. However, the disadvantage
of the use of AVI lies in the fact that the readers, like loop detectors,
are essentially point detectors whose effectiveness will be limited by
the spacing between successive readers. If detectors are spaced every
few yards then it would be possible to track the trajectory of a vehicle
and determine, in a very responsive manner, whether the vehicle is stopped.
This unrealistically, low spacing would provide a low mean time to detect
and a very high probability of detection. Such close spacing is neither
realistic nor fiscally responsible. Obviously, the mean time to detect
will increase as the spacing of the detectors increases. Recent studies
for TRANSCOM have found that readers spaced at 1½-mile intervals
on limited access freeways provide the best coverage for obtaining traffic
15.4.2 Washington State DOT Road Weather Information for Travelers
The Washington State Department of Transportation (DOT) has collaborated
with the University of Washington to provide travelers with comprehensive,
integrated road weather information. The DOT maintains one of the most
advanced traveler information web sites, which allows users to access
current and predicted road weather conditions on an interactive, statewide
22.214.171.124 System Components
The DOT owns 50 Environmental Sensor Stations (ESS) that collect air
temperature, atmospheric pressure, humidity, wind speed, wind direction,
visibility distance, precipitation, pavement temperature and subsurface
temperature. Some stations are equipped with Closed Circuit Television
(CCTV) for visual monitoring of pavement and traffic flow conditions.
The DOT is also a member of the Northwest Weather Consortium, which collects
and disseminates real time data from an extensive environmental monitoring
network. This network gathers and disseminates data from over 450 ESS
owned by nine local, state and federal agencies. A statewide communication
network transmits this ESS data to the Seattle Traffic Management Center
(TMC) and to a computer at the University's Department of Atmospheric
Sciences for data fusion and advanced modeling.
126.96.36.199 System Operations
A sophisticated computer model developed by the university ingests ESS
data to determine prevailing and predicted pavement temperatures and generate
high-resolution, numerical weather forecasts for the entire state. Observed
environmental data is integrated with other information including National
Weather Service (NWS) forecasts, satellite and radar images, video from
350 CCTV cameras, traffic flow data from inductive loop detectors, incident
and construction data, ten mountain pass reports, and audio broadcasts
from four Highway Advisory Radio (HAR) transmitters. As shown in 15-15,
route-specific traveler information is disseminated through the DOT's
Traffic and Weather web site (www.wsdot.wa.gov/traffic)
and via an interactive voice response telephone service (800-695-ROAD).
To make travel decisions, the public may access the web site to view state,
regional and local maps with environmental observations, weather and pavement
condition forecasts, video from freeway CCTV cameras, information on road
maintenance operations, and travel restrictions on mountain passes (e.g.,
reduced speed limits, prohibited vehicle types).
Figure 15-15: Example of Website Showing Current Weather
188.8.131.52 Transportation Outcome
Road weather data available through the web site and telephone service
allows users to avoid hazardous conditions, modify driving behavior, and
reduce crash risk. A user survey found that travelers feel safer when
they have access to real-time road weather information. The survey also
revealed that users frequently access the web site to prepare for prevailing
conditions along a selected route (i.e., 90 percent of respondents), for
general weather conditions (i.e., 86 percent), to check weather for a
specific recreational activity (i.e., 66 percent), and to determine travel
routes or travel time. Usage logs from the web site indicate that travelers
access condition data more frequently during adverse weather events. On
average, there were over 3,700 user sessions per day in February 2001.
During a snowstorm on Friday, February 16th (before a three-day weekend)
site usage increased to nearly 13,000 user sessions. The interactive telephone
service typically receives one million calls each winter (i.e., an average
of 8,000 calls per day) with call volumes increasing during inclement
conditions or major incidents. Maintenance managers also benefit from
access to detailed road weather data. This data serves as support for
operational decisions, such as resource allocation and treatment planning.
More effective and efficient resource decisions reduce labor, equipment
and material costs. The ability to employ proactive road treatment strategies,
such as anti-icing, also improves roadway mobility.
184.108.40.206 Implementation Issues
The web site project was funded by a grant from U.S. Department of Transportation
and a 20 percent match from Washington State DOT. To collect environmental
data for the site, the DOT wanted to procure ESS from different vendors
and display field data on a single user interface. Project managers developed
functional specifications and issued a request for proposals to furnish
ESS capable of communicating with an existing server using National Transportation
Communications for ITS Protocol (NTCIP) standards. After resolving technical
issues related to object definitions, one vendor successfully demonstrated
that their sensor stations could communication with another vendor's server.
This simplified management of environmental data and avoided the need
for additional hardware, software and communications infrastructure. By
using the open communication standard the DOT encouraged competition among
vendors that reduced ESS procurement costs by nearly 50 percent. The NTCIP
will also facilitate future expansion of the environmental monitoring
15.4.3 Tennessee DOT RWIS
In December 1990, a chain-reaction collision involving 99 vehicles prompted
the design and implementation of a fog detection and warning system on
Interstate 75 in southeastern Tennessee. The system covers 19 miles including
a three-mile, fog-prone section above the Hiwassee River and eight-mile
sections on each side.
TMC managers with Tennessee DOT access a central computer system that
collects data from two ESS, eight fog detectors, and 44 vehicle speed
detectors. By continually monitoring fog and speed sensor data, the computer
system predicts and detects conditions conducive to fog formation, and
alerts managers when established threshold criteria are met. Highway Patrol
personnel visually verify onsite conditions. The computer system correlates
field sensor data with pre-determined response scenarios, which include
advising motorists of prevailing conditions via flashing beacons atop
six static signs, two HAR transmitters, and ten DMS; reducing speed limits
using ten VSL signs; and restricting access to the affected highway section
with ramp gates.
TMC managers select pre-programmed DMS messages, pre-recorded HAR messages,
and appropriate speed limits (i.e., 50 mph or 35 mph) based upon response
scenarios proposed by the system. Under the worst-case scenario (i.e.,
visibility less than 240 feet), the Highway Patrol activates eight automatic
ramp gates to close the interstate and detour traffic to US Route 11.
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U.S. Department of Transportation, Federal Highway Administration, Washington,
2. Klein, L.A., Sensor Technologies and Data Requirements
for ITS, Artech House, Boston, MA, 2001.
3. FHWA "Operating the Highway System for Safety,
Reliability and Security: TEA-21 Reauthorization Proposal"; 2002
4. J. Kranig, E. Minge, and C. Jones, Field Test
of Monitoring of Urban Vehicle Operations Using Non-Intrusive Technologies,
FHWA-PL-97-018 (Washington, D.C.: U.S. Department of Transportation, Federal
Highway Administration, May 1997).
5. D. Middleton and R. Parker, Initial Evaluation
of Selected Detectors to Replace Inductive Loops on Freeways, FHWA/TX-00/1439-7
(College Station, TX: Texas Transportation Institute, April 2000).
6. NIT Phase II: Evaluation of Non-Intrusive Technologies
for Traffic Detection, Final Report, SRF No. 3683, Prepared by Minnesota
Department of Transportation and SRF Consulting Group, Inc. (Washington,
DC: U.S. Department of Transportation, Federal Highway Administration,
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Vehicle Detection Systems, Research Report FHWA/TX-03/2119-1, Draft
(College Station, TX: Texas Transportation Institute, Oct. 2002).
8. J. Grenard, D. Bullock, and A. Tarko, Evaluation
of Selected Video Detection Systems at Signalized Intersections: Final
Report, FHWA/IN/JTRP-2001/22bbbb (West Lafayette, IN: Indiana Department
of Transportation, Division of Research, and Purdue University, Nov. 2001).
9. D. Bullock and A. Tarko, Evaluation of Selected
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of Transportation, Division of Research, and Purdue University, Nov. 2001).
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(West Lafayette, IN: Indiana Department of Transportation, Division of
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of Operations (draft); FHWA; Washington, DC. January 2003.
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for Traffic Flow Monitoring and Management.
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Department of Transportation, District 7, Los Angeles, CA, February 1994.
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Engineers, Washington, DC, December 1994, pp 42-48.
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Detection. Moving Toward Deployment, Proceedings of the IVHS America 1994
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25. FHWA; "Best Practices for Road Weather Management,