**ITS Standards Impacting the Maintenance Community**

**Version 2.0**

July 2007

Paul Pisano, Team Leader

Federal Highway Administration (FHWA), Road Weather Management Program

Lynette C. Goodwin, Lead Transportation Engineer

Noblis, ITS Division

Blake P. Christie, Principal ITS Standards Engineer

Noblis, ITS Division

**INTRODUCTION**

Intelligent Transportation Systems (ITS) apply advanced communications
technologies to surface transportation networks in order to improve
roadway operations and safety. Standards facilitate the integration of
various ITS components to achieve the interoperability required for such
systems to function consistently between agencies and across the nation.
The U.S. Department of Transportation (DOT) ITS Standards Program
promotes extensive use of open, non-proprietary standards. ITS
standards, which are developed by industry consensus, define how
elements of a system operate within the framework of the National ITS
Architecture. These standards ensure that equipment and systems
purchased from different vendors are capable of exchanging data
automatically, consistently, and reliably. The use of standards also
promotes competition among system developers, encourages industry growth
by minimizing development costs, and results in cost savings over the
life of public agency investments.

This paper provides an overview of ITS standards and the adoption
process: highlighting the ways in which standards are important to the
maintenance community, identifying relevant standards, and describing
resources for technical support. The paper focuses primarily on the
Environmental Sensor Station (ESS) standard and related standards that
facilitate use of ESS data in Road Weather Information Systems (RWIS)
and other systems.

**OVERVIEW OF ITS STANDARDS**

ITS standards allow different technologies and system components to
interact and exchange information. A standards-based approach to
deployment and integration allows transportation agencies to more easily
accommodate future equipment replacements, systems upgrades, and system
expansions. With standards-based systems, agencies can also extend the
reach and capabilities of their ITS infrastructure. An example of such
integration is an ESS that reports current pavement conditions to a
Traffic Management Center (TMC), which sends an advisory to a Dynamic
Message Sign (DMS). Various standards for different applications (e.g.,
maintenance management, traffic management, traveler information)
address interfaces in the National ITS Architecture. This section
outlines the standards adoption process and introduces the standards
architecture.

**[Standards Adoption Process]{.underline}**

ITS standards are developed through cooperative agreements between the
U.S. DOT ITS Standards Program and the following Standards Development
Organizations (SDOs):

-   American Association of State Highway and Transportation Officials
    (AASHTO)

-   American Public Transportation Association (APTA)

-   American Society for Testing and Materials (ASTM)

-   Institute of Electrical and Electronics Engineers (IEEE)

-   Institute of Transportation Engineers (ITE)

-   National Electrical Manufacturers Association (NEMA)

-   Society of Automotive Engineers (SAE)

The four-step process depicted in Figure 1 includes publication,
testing, deployment, and adoption. Publication begins with
identification of needs and analysis of technical requirements by an
SDO. These requirements are documented in a draft standard, which is
then sent to ballot. During balloting, working group members review the
technical merits of the draft standard and either reject or approve it.
Approved standards are published and can be purchased from the lead SDO.
Then the standard is tested in early deployments. Testing measures the
operation, correctness, and completeness of a standard under realistic
operating conditions. Lessons learned from deployment and testing result
in revision to the standard. As standards mature, vendors compete to
provide a range of equipment with varying functions. When sufficient
standards-compliant products are available and the standard is widely
deployed, the U.S. DOT considers rulemaking to promote the production of
technically and commercially viable ITS standards and equipment.

![](media/image1.png){width="6.665277777777778in"
height="0.8583333333333333in"}

As of June 2007, eighty-eight (88) ITS standards were published and
eight (8) of these had been approved. Three (3) standards were in
ballot, or being voted upon by a working group, and five (5) were under
development.

**[National ITS Architecture]{.underline}**

The National ITS Architecture is the overall structure used to plan,
configure, and integrate Intelligent Transportation Systems. The
architecture helps transportation agencies define system stakeholders
and their relationships in order to facilitate integration of systems
locally, regionally, and nationally. As shown in Figure 2, the
architecture defines subsystems where functions occur, the data flows
that connect subsystems to form an integrated system, and the key
interfaces for standardization. Figure 2, also known as the "sausage
diagram", is a high-level view of the National ITS Architecture that
illustrates where Maintenance and Construction Management fits into the
overall ITS operational concept.

As seen in the figure, subsystems are grouped into four interface
classes: centers, field, vehicles, and travelers. The lines in Figure 2
represent four types of architecture flows or interfaces between
subsystems: wireline communications (i.e., fixed-point to fixed-point),
wide area wireless communications (i.e., mobile), dedicated short-range
communications, and vehicle-to-vehicle communications. *These
architecture flows indicate where interoperability is needed and where
ITS standards are required.*

![](media/image2.png){width="6.019291338582677in"
height="4.099212598425197in"}

**Figure 2 -- High-Level View of the National ITS Architecture**

**THE IMPORTANCE OF ITS STANDARDS TO THE MAINTENANCE COMMUNITY**

ITS standards are valuable because they allow maintenance personnel to
deploy equipment and integrate systems that operate consistently across
technical, jurisdictional, and institutional boundaries. ITS standards
can reduce agency costs and increase competition by prompting vendors to
provide implementers with more product and service alternatives.
Although using standards may increase initial project costs, total life
cycle cost (i.e., procurement, maintenance, and expansion costs) will be
minimized. Transportation projects employing ITS standards are also
eligible for federal funding through the Highway Trust Fund. The
benefits of using ITS standards will increase as more interfaces are
standardized for the road maintenance community.

By allowing systems to exchange data in a standard format and syntax,
ITS standards facilitate interchangeability and interoperability,
reducing dependence on proprietary equipment and software.
Interchangeability allows devices of the same type, made by different
vendors, to be substituted for one another and interact on the same
communication channel. For example, an agency could deploy Environmental
Sensor Stations from three manufacturers in a statewide RWIS. With ITS
standards, maintenance managers could use one central system to access
data from all of the Environmental Sensor Stations. Interoperability is
the ability of systems or devices to provide information to, and receive
information from, other systems or devices such that they effectively
operate as a single system. For example, an interoperable system would
allow a maintenance garage to send road weather data to a Traffic
Management Center (TMC) and receive traffic flow data from the TMC,
regardless of the equipment manufacturer, and without multiple data
conversion steps.

Applicable standards for road maintenance cover two types of
architecture flows: center-to-field (e.g., between a maintenance garage
and an ESS) and center-to-center (e.g., between a maintenance garage and
a TMC). Currently, there are no ITS standards available for
center-to-vehicle architecture flows. Standards for these flows may be
developed in the future. There is one standard for vehicle-to-field
architecture flows (i.e., Dedicated Short Range Communications or DSRC).
However, no maintenance applications have been developed for this
interface.

**[NTCIP Standards]{.underline}**

The following standards have been developed under an umbrella effort
entitled *National Transportation Communication for ITS Protocol*, also
known as NTCIP. There are three types of NTCIP standards: data
standards, message standards, and communication standards. Data
standards include data dictionaries and object standards that define
data elements, and groups of data elements, for specific device types.

Message standards consist of objects that are grouped into logical
messages, which are comprised of data elements. Message Set Standards
define logical groupings of data elements for preset messages used for
center-to-center communications. Message set standards are used in
conjunction with center-to-center communication standards.

Communication standards provide the means (i.e., protocols) for sending
or receiving messages. NTCIP use of a given protocol, or set of
protocols, is called a profile standard. Protocols describe how messages
are encoded for transmission, how they are transmitted (e.g., dial-up
telephone lines, fiber optic cables), and how they are decoded by the
receiver. Profiles define how to use or combine protocols to deliver a
message or object.

**[Center-to-Field Standards]{.underline}**

Maintenance managers utilize center-to-field standards to configure,
control, and collect data from multiple field devices via a central
computer. Interfaces between the Maintenance and Construction Management
center that performs environmental monitoring and the Roadway subsystem
are covered by center-to-field standards. The architecture flows that
are the most relevant for the maintenance community include:

-   environmental sensors control![](media/image5.wmf){width="3.15in"
    height="0.8701388888888889in"}

-   environmental conditions data

-   roadway treatment system control

-   roadway treatment system status

-   roadway information system data

These are the architecture flows that apply to managing Environmental
Sensor Stations, observing weather and pavement conditions, monitoring
water levels near roadways, controlling and monitoring automated
anti-icing systems, and disseminating road weather information via
Dynamic Message Signs (DMS). There are several standards associated with
these architecture flows, and multiple standards may apply to any one of
these flows.

The center-to-field data standards associated with the architecture
flows above are:

-   NTCIP 1201 -- Global Object Definitions

-   NTCIP 1203 -- Object Definitions for Dynamic Message Signs

-   NTCIP 1204 -- Environmental Sensor Station Interface Standard

[NTCIP 1201 -- Global Object Definitions]{.underline}: Global Object
Definitions cover data elements that are common to many different types
of ITS devices. At an early stage, the NTCIP SDOs decided that, for the
purposes of configuration control, it would be best to put common data
elements used by multiple equipment standards in a single "global"
standard of elements. This allows commonly used elements to be updated
across the entire set of center-to-field standards. The SDOs approved
the first version of NTCIP 1201 in 1997 and approved an amendment in
2001. A second version was recommended for ballot in 2002 and approved
in 2005. The published version was made available in December 2006.

[NTCIP 1203 -- Object Definitions for Dynamic Message
Signs]{.underline}: Data elements for three types of DMS are defined in
the Object Definitions for Dynamic Message Signs standard. NTCIP 1203
was initially approved as a recommended standard in 1997 and amended in
2002 based on user comments from deployment and testing. This is the
most mature and widely-deployed ITS standard. The first version of the
standard has been deployed in several states including Arizona, Georgia,
Illinois, Virginia, and Washington State. Version 2 reflects lessons
learned from early deployments and adds new features. The second version
includes a concept of operations (i.e., user needs), functional
requirements, traceability between the needs and the interface
specifications, and expanded functionality (e.g., use of graphics).
Version 2 was accepted as a recommended standard in March 2007.

[NTCIP 1204 -- Environmental Sensor Station Interface
Standard]{.underline}: The standard that defines how a central computer
interfaces with a field device to control and monitor pavement sensors,
weather stations, air quality monitors, and other equipment (e.g.,
anti-icing systems) is entitled Environmental Sensor Station Interface
Standard. The first version of NTCIP 1204 was approved and published by
SDOs in 1998 and amended in 2001. This standard has been implemented by
DOTs in Alaska, Minnesota, Washington State, and Wisconsin. Case studies
of Minnesota DOT and Washington State DOT have documented how this
standard has been used in their deployments. The Minnesota DOT used
NTCIP 1204 to avoid pitfalls associated with proprietary systems and
sole-source vendors. Over 70 NTCIP-compatible ESS and numerous legacy
ESS were seamlessly integrated into a single RWIS. The Washington State
DOT used the standard to facilitate communication between ESS made by
one vendor and a central server from another vendor. This allowed the
DOT to manage environmental data from a single platform and reduce
procurement costs by nearly 50 percent due to increased competition
between vendors.

A second version of NTCIP 1204, which incorporated lessons learned from
early deployments and testing, was accepted as a recommended standard in
March 2005 and approved in March 2006. Version 2 also included a concept
of operations (i.e., user needs) and requirements that explicitly traced
from needs to specific interface specifications (i.e., data elements and
dialogs). Version 3 of NTCIP 1204, which includes detailed test
procedures, was released for review and comment in June 2007. During the
user comment period, the Florida DOT carried out the test procedures on
two independent device implementations: one with NTCIP 1204v1 and the
other with partially implemented NTCIP 1204v2 objects.

For the center-to-field architecture flows identified above, Object
Definitions standards would be used in conjunction with the Global
Objects standard and selected center-to-field communications profile
standards.

**[Center-to-Center Standards]{.underline}**

Because many events can be related (e.g., increased congestion during
rainfall, more frequent crashes on icy pavement), sharing information on
weather events and mitigation strategies with managers in neighboring
jurisdictions can foster institutional coordination. Center-to-center
standards facilitate communication between two or more management
centers and allow road weather data to be integrated with Advanced
Traveler Information Systems (ATIS) and Advanced Traffic Management
Systems (ATMS). These standards allow maintenance managers to interface
with traffic operations personnel, inform operators of weather-related
conditions affecting traffic flow and road safety, and increase the
operational efficiency of all center managers.

Interfaces between the Maintenance and Construction Management center
and the Traffic Management center are covered by center-to-center
standards. These architecture flows, which can also be used to
communicate with another Maintenance and Construction Management center
or an Information Service Provider center, include:

-   road weather information

-   roadway maintenance status

These architecture flows are utilized to send weather data, road
condition information, and the status of maintenance fleet operations
from a maintenance division to other transportation system operators.
They can also be used to send information from a Traffic Management
Center to a maintenance division to support efficient management of
maintenance activities. The center-to-center standards associated with
these flows are:

-   ITE Traffic Management Data Dictionary (TMDD)

-   SAE J2354 -- Message Sets for Advanced Traveler Information Systems
    (ATIS)

-   NTCIP 2304 -- Application Profile for DATEX ASN

-   NTCIP 2306 -- Application Profile for XML in ITS Center to Center
    Communications

[ITE Traffic Management Data Dictionary (TMDD)]{.underline}: The
center-to-center standard that is most important to maintenance managers
is the Traffic Management Data Dictionary (TMDD). All management centers
that share information can use this standard, regardless of their
function. Version 1 of the TMDD standard is organized into four sections
that define elements for the traffic network (i.e., links and nodes),
events disrupting the network (i.e., events, incidents, and notification
alarms), traffic control devices (e.g., signals, detectors, ramp
meters), and information gathering or dissemination devices (i.e., ESS,
CCTV, DMS, Highway Advisory Radio).

The TMDD data elements and associated message sets are used together to
provide interoperability. The message sets combine TMDD data elements
into messages for transmission between management centers. The Version 1
TMDD message sets include six message groups: roadway network, network
state, network events, traffic request, traffic device status, and
traffic control. The message sets have been implemented by the Texas DOT
and in over 30 centers in New York, New Jersey, and Connecticut as part
of TRANSCOM---a coalition of transportation and public safety agencies.
Version 2 of the TMDD was proposed as a provisional standard in January
2005. In September 2006, a workshop was held to capture user needs that
served as input to the Concept of Operations for Version 3 of the TMDD.
Version 3 incorporated lessons learned by deployers and addressed
additional areas of scope, including extending the standard to include
data elements and message sets from the *Clarus* Initiative
([www.clarusinitiative.org](http://www.clarusinitiative.org/)) and the
Archived Data User Service standards effort.

[SAE J2354 -- Message Sets for Advanced Traveler Information Systems
(ATIS)]{.underline}: The Message Sets for Advanced Traveler Information
Systems (ATIS) standard provides traveler information messages,
including road condition messages, in both Abstract Syntax Notation 1
(ASN.1) and eXtensible Mark-up Language (XML) formats. SAE J2354 was
originally published in 1999 and revised in 2004. Version 2 is currently
under revision. This message set standard can be used to support data
dissemination to the public via ATIS, such as agency web sites and
511---the national traveler information telephone number. The messages
contained within SAE J2354 address all stages of travel (i.e.,
informational, pre-trip, en route), all types of travelers, all
categories of traveler information, and all delivery platforms (e.g.,
in-vehicle devices, portable electronic devices, kiosks).

The SAE J2354 standard includes weather information, either by road
segment or by larger geographic area, as transmitted to Information
Service Provider centers. Maintenance managers can use the standard to
disseminate road weather information (e.g., hazardous winter road
conditions) to the public via this type of center. The City of San
Francisco and the Gary-Chicago-Milwaukee Corridor have deployed the SAE
J2354 standard.

The TMDD and SAE J2354 standards have overlapping content with regards
to traveler information. Managers should select one of the standards
based upon specific operational needs. The TMDD standard is designed for
information exchange between centers, while the SAE J2354 standard is
intended primarily for disseminating traveler information to end users,
usually via an Information Service Provider.

[NTCIP 2304 -- Application Profile for DATEX ASN:]{.underline} This
application profile includes requirements for the traditional approach
to communications between two management subsystems (i.e., data encoded
in ASN.1). An example of this is a Maintenance and Construction
Management center connected to a Traffic Management center. This
application profile lists the requirements for data exchange among
systems. The first version of NTCIP 2304 was approved in December 2002
and a revised version (v01.08) was published in February 2006.

[NTCIP 2306 -- Application Profile for XML in ITS Center to Center
Communications]{.underline}: The Application Profile for XML in ITS
Center to Center Communications specifies communications interfaces
(i.e., message form, message use, and transport) encoded in XML for
real-time management of public roads and transit systems. Message
content is defined in other standards, such as the TMDD and SAE J2354.
NTCIP 2306v01.68 was accepted as a recommended standard in March 2006.
It is expected that Version 1 will be approved and published in 2007.

**[Center-to-Vehicle Standards]{.underline}**

In the future, center-to-vehicle standards will allow maintenance
managers to monitor mobile environmental sensors and track the location
and operational status (e.g., plow up/down, chemical application rate)
of maintenance vehicles that use different technologies. These standards
will allow managers to communicate with a single vehicle, a group of
vehicles, or all vehicles, independent of the brand of equipment
installed, as they travel along their designated routes. The U.S. DOT's
Vehicle Infrastructure Integration (VII) Initiative
([www.its.dot.gov/vii/](http://www.its.dot.gov/vii/)) has the potential
to enhance center-to-vehicle communications.

Architecture flows between the Maintenance and Construction Management
center and Maintenance and Construction Vehicles would be covered by
center-to-vehicle standards. These architecture flows, which are
candidates for future standardization, include:

-   maintenance and construction dispatch information

-   maintenance and construction vehicle location data

-   maintenance and construction vehicle operational data

-   environmental probe data

**ITS STANDARDS RESOURCES**

Deploying standards can seem overwhelming at first. For this reason, a
host of resources have been developed to assist maintenance personnel in
implementing ESS and other ITS standards. As a start, the FHWA Road
Weather Management Program created a brochure that describes
communications standards, siting standards, and calibration standards
for RWIS applications. This resource can be accessed on the Road Weather
Management Program web site at
[www.ops.fhwa.dot.gov/weather/Publications/RWIS_brochure.pdf](http://www.ops.fhwa.dot.gov/weather/Publications/RWIS_brochure.pdf).
Many other resources provide more detailed assistance, as described
below.

An ITS Standards Advisory on ESS highlights standards development,
testing, and deployment activities. It also includes guidance on working
with ESS vendors, information on the ESS Working Group, and a table of
Standards Applicable to ESS Deployments. The advisory is available at
[www.standards.its.dot.gov/Documents/advisories/ess_advisory.pdf](http://www.standards.its.dot.gov/Documents/advisories/ess_advisory.pdf).
Specifications for RWIS that reference NTCIP standards can be found on
the Aurora Program web site,
[www.aurora-program.org/matrix.cfm]{.underline}. These specifications
have been utilized by several state DOTs.

The NTCIP Guide (i.e., NTCIP 9001v03.02) was accepted as a recommended
information report in October 2002. The NTCIP Guide was created to
assist decision makers, planners, specification writers, and
implementers in understanding the various NTCIP standard publications
and how to use them. The guide, which is currently under revision, is
organized into 10 chapters including an "Executive Summary" for decision
makers, "Understanding NTCIP" for system planners, "Procuring NTCIP" for
specification writers, "Designing NTCIP" for communications engineers,
and "Implementing NTCIP" for hardware and software developers and system
integrators. The other chapters discuss applications for center-to-field
and center-to-center communications, as well as other issues such as
intellectual property rights, legacy and system migration issues,
testing and conformity, and configuration management. A copy of the
guide can be downloaded from
[www.ntcip.org/library/guide.asp]{.underline}.

**[Training and Software]{.underline}**

Training and support tools are available for transportation agencies
that are planning, deploying, or upgrading ITS. The FHWA and the
National ITS Architecture Team (Iteris, Inc. and Lockheed Martin)
created Turbo Architecture, an interactive software tool to help system
designers with development of a regional or project Architecture to
facilitate usage of the National ITS Architecture. For more information
on Turbo Architecture, visit
[http://mctrans.ce.ufl.edu/featured/turbo*/*](http://mctrans.ce.ufl.edu/featured/turbo/).

Transportation agencies can also receive guidance through the
Integrating NTCIP Compliant Hardware (INCH) Project that teaches
managers how to specify, purchase, deploy, and test NTCIP-conformant
hardware. Information on the INCH Project can be found online at
[www.enterprise.prog.org](http://www.enterprise.prog.org/) under
"Completed Projects".

The Institute of Transportation Engineers (ITE) offers free one-day
courses including an overview of ITS standards and a course on
center-to-center standards. The ITS Standards Overview course is
intended for transportation professionals and policy makers involved in
ITS deployment. The Center to Center course is an introduction to the
use of application profile standards to exchange data among ITS centers.
This course also includes an introduction to the TMDD and ATIS
standards. Additional information can be found at
[www.ite.org/standards/courseschedule.asp](http://www.ite.org/standards/courseschedule.asp).

**[Technical Assistance]{.underline}**

The ITS Standards Field Support Team provides intensive consultation to
aid state and local transportation agencies with a wide range issues
including system assessment, specification development, contract advice
and review, test plan design, compliance evaluation, and other technical
issues. This team is comprised of FHWA specialists who are prepared to
provide short-term, on-call assistance in the area of ITS Standards. The
goal of the team is to support and facilitate the deployment of
Intelligent Transportation Systems that advance national and local needs
while implementing ITS Standards. More information on the Field Support
Team can be found at
<http://ops.fhwa.dot.gov/int_its_deployment/standards_imp/stdsteam.htm>.
To request support from the ITS Standards Field Support Team, contact
your FHWA Division Office or contact Tom Stout, Office of Transportation
Management, at tom.stout@dot.gov or 202-366-6054.

**[Peer-to-Peer Program]{.underline}**

Through the ITS Peer-to-Peer Program, deployers also can request
assistance from peers, in the public and private sectors, who have
successfully overcome the challenges of designing and implementing
various types of Intelligent Transportation Systems. Over 120 ITS
professionals lend their technical expertise to the Peer-to-Peer
Program. Additional Peer-to-Peer Program information can be obtained by
calling 1-888-700-PEER, visiting
[www.its.dot.gov/peer/peer-t.htm]{.underline}, emailing
p2p@volpe.dot.gov, or contacting Tom Stout, Office of Transportation
Management, at tom.stout@dot.gov or 202-366-6054.

**CONCLUSION**

[]{.mark}

Nearly 90 ITS standards have been developed by SDOs for use by
transportation agencies that deploy and integrate various technologies
to create interoperable management systems. ITS standards are organized
in the framework of the National ITS Architecture, which groups
subsystems into four categories: centers, field, vehicles, and
travelers. Architecture flows denote areas where ITS standards are
required to achieve interoperability.

Two types of architecture flows are important to the maintenance
community: center-to-field and center-to-center. Emerging communications
standards will support center-to-vehicle applications as the VII
Initiative advances in the future.

The center-to-field standards that are relevant for maintenance
activities include:

-   NTCIP 1201 -- Global Object Definitions

-   NTCIP 1203 -- Object Definitions for Dynamic Message Signs

-   NTCIP 1204 -- Environmental Sensor Station Interface Standard

-   NTCIP Center-to-Field Standards Group

Architecture flows between Maintenance and Construction Management
centers and other centers, such as Traffic Management Centers and
Information Service Providers, are used to share road weather data and
maintenance fleet status information. Center-to-center standards allow
transportation managers to interface and coordinate operational
responses to inclement weather and other conditions. The
center-to-center standards relevant for maintenance activities include:

-   ITE Traffic Management Data Dictionary (TMDD)

-   SAE J2354 -- Message Sets for Advanced Traveler Information Systems
    (ATIS)

-   NTCIP 2304 -- Application Profile for DATEX ASN

-   NTCIP 2306 -- Application Profile for XML in ITS Center to Center
    Communications

-   NTCIP Center-to-Center Standards Group

Numerous resources are available to assist maintenance personnel with
implementation of ITS standards. Documents, training courses, software
and other technical assistance can be used to guide state DOTs as they
deploy and integrate ITS components. Using ITS standards in RWIS
applications will ultimately support a host of road weather management
solutions that state DOTs are implementing including weather-responsive
traffic management applications, Maintenance Decision Support Systems
(MDSS)
([www.rap.ucar.edu/projects/rdwx_mdss](http://www.rap.ucar.edu/projects/rdwx_mdss)),
mobile data communications for maintenance vehicles, disseminating
weather-related traveler information, and utilizing the nationwide road
weather observing system known as *Clarus*
([www.clarusinitiative.org](http://www.clarusinitiative.org/)). These
solutions will benefit transportation agencies and the traveling public
by improving safety, mobility, and productivity.

**REFERENCES**

1.  FHWA, "An Introduction to Standards for Road Weather Information
    Systems (RWIS)," Road Weather Management Program, July 2002,
    [www.ops.fhwa.dot.gov/weather/publications/rwis_brochure.pdf](http://www.ops.fhwa.dot.gov/weather/publications/rwis_brochure.pdf).

2.  ITE, "Traffic Management Data Dictionary (TMDD) and Message Sets for
    External Traffic Management Center Communications (MS/ETMCC)," 2007,
    [www.ite.org/tmdd/](http://www.ite.org/tmdd/).

3.  NEMA, "Minnesota DOT Statewide R/WIS Project," NTCIP 9008 v01.06,
    January 2003,
    [www.ntcip.org/library/documents/pdf/9008v01-06.pdf](http://www.ntcip.org/library/documents/pdf/9008v01-06.pdf).

4.  NEMA, "NTCIP Documents Web Site," July 2007,
    [www.ntcip.org/library/documents/](http://www.ntcip.org/library/documents/).

5.  NEMA, "Washington State DOT Statewide ESS Procurement," NTCIP 9009
    v01.05, January 2003,
    [www.ntcip.org/library/documents/pdf/9009v01-05.pdf](http://www.ntcip.org/library/documents/pdf/9009v01-05.pdf).

6.  U.S. DOT, "ITS Standards," National ITS Architecture web site,
    Version 5.0, November 2003,
    <http://itsarch.iteris.com/itsarch/html/standard/standard_b.htm>.

7.  U.S. DOT, "NTCIP Center-to-Field Standards Groups," National ITS
    Architecture web site, Version 5.0, November 2003,
    <http://itsarch.iteris.com/itsarch/html/standard/ntcipc2f.htm>.

8.  U.S. DOT, "NTCIP Market Packages," National ITS Architecture web
    site, Version 5.0, October 2003,
    <http://itsarch.iteris.com/itsarch/html/mp/mpindex.htm>.  

9.  U.S. DOT ITS Standards Program, "Environmental Sensor Station (ESS):
    ITS Standards Advisory," March 2003,
    [www.standards.its.dot.gov/Documents/ess_advisory.pdf](http://www.standards.its.dot.gov/Documents/ess_advisory.pdf).

10. U.S. DOT ITS Standards Program,, "ITS Standards: A Brief Stroll
    through the Different Document Types," February 1999,
    [www.standards.its.dot.gov/Documents/stddef.pdf](http://www.standards.its.dot.gov/Documents/stddef.pdf).

11. U.S. DOT ITS Standards Program, "Leading the Way: Profile of an
    Early ESS Deployer (Minnesota DOT)," FHWA-OP-02-017,
    [www.standards.its.dot.gov/Documents/Early%20Depl%20FLEEGE.pdf](http://www.standards.its.dot.gov/Documents/Early Depl FLEEGE.pdf).

12. U.S. DOT ITS Standards Program, "Leading the Way: Profile of an
    Early ESS Deployer (Washington State DOT)," FHWA-OP-02-014,
    [www.its-standards.net/Documents/Early%20Depl-%20SENN.pdf](http://www.its-standards.net/Documents/Early Depl- SENN.pdf).

13. U.S. DOT ITS Standards Program, "Life Cycle of ITS Standards from
    Initial Development to U.S. DOT Adoption," May 2001,
    [www.standards.its.dot.gov/Documents/lifecycle.pdf](http://www.standards.its.dot.gov/Documents/lifecycle.pdf).

14. U.S. DOT ITS Standards Program, "Published Standards Documents,"
    November 2003,
    [www.standards.its.dot.gov/Documents/publish.pdf](http://www.standards.its.dot.gov/Documents/publish.pdf).

15. U.S. DOT ITS Standards Program, "Test Report Synopsis for NTCIP
    Environmental Sensor Station (ESS) Standards," November 2003,
    [www.standards.its.dot.gov/testESS.htm](http://www.standards.its.dot.gov/testESS.htm).