Добавил:
ivanov666
Опубликованный материал нарушает ваши авторские права? Сообщите нам.
Вуз:
Предмет:
Файл:Архитектура интеллектуальных транспортных систем = Intelligent Transport Systems’ Architecture. Учебное пособие
.pdf
11
Fig. 1.2. Relationships between different ITS architecture viewpoints
and other aspects of ITS deployment
To gain maximum benefit from a high-level architecture it should be
developed before any work is done to procure the components and
communications needed for the ITS deployment.
Low-level (or component) ITS architectures contain the actual designs
and specifications for hardware, software, data exchange and
communications. They define more narrowly the technologies required
including the use of and the ITS related standards that are to be used
particularly for interfaces and communications. A low-level architecture could
be developed by the commissioning body, if it has the expertise, but it is more
common for design specifications to be developed from a high-level
architecture by the systems integrator or system supplier (and may not always
be in the public domain.
There are two types of high level ITS architecture in common use around
the world – which offer two basic but different approaches – a framework
architecture and a ‘model’ architecture – both of which provide a basis for the
development of ITS architectures that can be adapted to suit particular ITS
implementations. Some of these ITS architectures can be specific to a class of
ITS applications. This is because they support implementation of a specific
service, such as traffic control centers, car park management, or public
transport fleet management.
12
1.2. Framework ITS architectures
A framework ITS architecture will use a set of user-led service
specifications for different ITS applications that provide a flexible basis for
further refinement and development. A framework approach is particularly
suited to circumstances where a ‘top-down’ universal approach is not feasible.
A framework ITS architecture provides the basis for stand-alone ITS master
plans to be developed at the appropriate level (national, regional or local).
It can also facilitate cross-border integration and an open market for
interoperable ITS services and equipment. The best known example of
a framework ITS architecture is the European ITS Framework Architecture.
A number of countries are using the FRAME architecture as the starting point
for their own national ITS architecture developments – these include
Australia, Austria, Czech Republic, France, Hungary, Italy and Poland.
Framework ITS architectures have the following advantages:
it makes it possible to achieve the harmonious integration of systems
by defining where common standards, norms and practices can be used;
it prompts the resolution of important issues - such as stakeholder
relationships and responsibilities for communications infrastructure provision;
they can be easily developed and adapted to provide a framework ITS
architecture in different national contexts;
users can expand a framework ITS architecture to support additional
services;
they can be used to develop low-level ITS (or component)
architectures that are adapted for particular ITS implementations – giving
users the freedom to create their own component configurations and specify
the associated communications networks;
they can be used to explore alternative component configurations and
associated communications networks - making it possible to investigate the
options leading to an optimum ITS architecture for a particular deployment.
Many regions of the world have developed ‘model’ ITS architectures
that are adapted to the needs and requirements of their region and institutional
arrangements. They are generally more prescriptive in how ITS deployments
must be rolled out when compared with a framework ITS architecture. They
often contain a physical viewpoint that will define the components used to
13
deliver the services the architecture is able to support. For example the USA’s
National ITS architecture (www.iteris.com/itsarch/) is fixed and its use is
obligatory if federal financial support for ITS deployment is sought. It defines:
the functions of the system and sub-system components;
where these functions reside (at the roadside, in a traffic management
center, or in a vehicle);
the interfaces and information flows between subsystems;
the communications requirements for the information flows in order
to address the underlying user service requirements;
where standardization of equipment, interfaces and communications
at the national level will bring benefits.
Other regions which have, or are, considering developing ‘model’
national architectures include Canada, Chile, Japan, Korea and Mexico.
A framework ITS architecture and a ‘model’ ITS architecture both
provide a structure (or template) from which ITS architectures adapted for
particular ITS deployment can be generated. This allows the user the
flexibility to tailor the architecture for specific deployments without losing the
benefit of its common features - such as the interfaces for system components
and communications. Standard interfaces are very important for consistent
systems integration and will have greater importance in the future with the
advent of cooperative systems ("C-ITS" for short, and known as "connected
vehicles" in the USA). This is because of the need for services to be delivered
in the same way, everywhere within a region, for example the USA, Europe,
Australia and Japan. They make the exchange of information possible at an
affordable and effective level.
ITS architectures that are adapted and customized from a framework ITS
architecture have the following characteristics:
they can either be used for a particular ITS implementation or as the
basis for a series of ITS implementations that use some or all of a common set
of functionality (such as regional or urban ITS deployments);
it is possible to modify the content and add functionality to support
additional services before defining the physical viewpoint;
although adding additional functionality is not difficult, it is often
advantageous to enlist the help of specialist consultants;
a tool will need to be provided to enable the framework ITS
architecture to be adapted and this can simplify its use and application.
14
The FRAME architecture is the best known examples of a framework
ITS architecture being used as the 'master" for regional and urban ITS
deployments across Europe and other countries, as well as European research
projects.
ITS architectures that are customized from a 'model' ITS architecture
have the following characteristics:
they can either be used for a particular ITS implementation or as the
basis for a series of ITS implementations that use some or all of a common set
of components and communications networks (such as regional or urban ITS
deployments)
the content is more restricted in terms of its functionality although
there may be limited options for varying the component configuration – for
example the options for the communications network are restricted to what is
compatible with the common specifications
as a result of the content being restricted, a 'model' ITS architecture
cannot be easily expanded by its users to include previously unsupported
services – this has to be done by specialist consultants
if not already available, a tool will need to be provided to enable the
'model' ITS architecture to be adapted and this can simplify its use and
application
The US National ITS architecture is probably the best known examples
of a 'model' ITS architecture, being used as the ‘master’ for regional and urban
ITS deployments in the USA, Canada, Chile, Israel and other countries.
The choice of which particular ITS architecture development approach
to use is dependent on the ultimate objective of the responsible authority or
organization – and will depend on how the ITS architecture is to be used and
what is to be the starting point for its creation. In some cases the use of a
'model' ITS architecture is mandatory. For example in the USA, federal
financing for ITS deployments is conditional on using of the National
Architecture.
A framework ITS architecture is generally more flexible than a 'model'
ITS architecture – though both can be expanded to include extra and/or
alternative services. Since framework ITS architectures are not prescriptive
they can facilitate the search for an optimum component/communications
solution to an ITS implementation. Using a framework ITS architecture
15
requires some training from experts since its users need to understand the ITS
architecture creation process and how to use it. (See Resources) A 'model' ITS
architecture is the least flexible since it contains restricted component
configuration and communications specifications. But if no changes to the
supported services are needed, they are often easier to use and do not require
its users to be expert in the creation of an ITS architecture (fig.1.3).
Fig. 1.3. World-wide ITS architecture activities
For economies in transition it is important to go back to basics to
understand the scope for ITS to improve local transport problems and respond
to user needs. These must be fully reflected in the ITS architecture’s design
and specifications. This is necessary so that ITS deployments are planned and
well suited to the local context. It should be noted that a 'model' ITS
architecture from one region may require considerable modification to adapt
it so that it can be suitable for use elsewhere in other implementations of ITS.
16
2. ITS STANDARDS
2.1. About standards
Standards have an important part to play in Road Network Operations.
They are firm specifications and requirements. They ensure that systems and
equipment are interoperable (sometimes with interchangeable components) –
even when they are from competing vendors. A good understanding of the
different types of ITS standards and their current stage of development is
necessary to develop a robust ITS deployment strategy. The use of accepted
standards for communications protocols and data message sets is essential, for
example, when setting up data exchange arrangements between road network
operators and related service providers– such as traffic management centers
and traffic information providers. The standards ensure that information is
correctly received and interpreted by the different software systems.
Major ITS standardization programs are underway in Europe, the US
and Japan to address the growing need for ITS standards. They are negotiated
through international standards organizations. These bodies have produced a
broad range of standards – from traveler information to vehicle safety systems.
Many standards emerge from ITS development activities - providing the basis
for widespread deployment and support activities. Prototype development and
field-testing help ensure that standards are fit for purpose and ready for
adoption. In some cases, standards are mature enough for their use to be
mandated by governments – to accelerate the deployment of ITS systems to
improve mobility, safety and efficiency.
The goal of global harmonization around standards for some ITS
applications – such as satellite navigation and cooperative vehicle systems –
has gained increasing support from governments and industry. A number of
governments now formally coordinate their positions on standards, whilst the
automotive industry has come together with digital map suppliers and mobile
telecommunications and internet companies – to address the challenges of the
more fast-moving technologies, such as smartphone-vehicle integration.
Changes in consumer expectations – and technical developments –
create the need for standards to enable new ITS applications to be developed
and deployed. Growing levels of vehicle connectivity and a focus on
17
sustainability and “green ITS” provide opportunities for optimizing transport
networks. For instance, data obtained through crowd-sourcing and vehicle
probes can be used by network operators and in user applications, to inform
drivers about road and traffic conditions and alternative routing.
Connected vehicles demand new technical solutions, supported by
standards, to ensure fast, reliable V2X communications in safety-critical
situations.
Automated vehicles rely on well-understood human interfaces and
applications that can be certified as safe and reliable to operate on public
highways. As transport solutions take advantage of the opportunities provided
by the “Internet of Things”, more information interfaces must be managed.
Examples include consumer devices such as smartphones, which interface
with vehicle display systems and connect with transport information
providers.
The growing body of ITS standards is a valuable resource for the
increasing number of organizations deploying ITS. A review of emerging
standards can also provide an insight into new industry and technology
developments and trends. Standardization may relate to some or all of
a technical specification and the operational guidelines.
ITS standards will continue to evolve quickly to keep pace with new
technologies and applications emerging from within and outside the transport
community.
The motivation for standard setting varies. It includes securing better
safety, reducing costs, and market enhancement of products. For example, for
safety reasons, a driver should not be faced with complicated in-vehicle route
guidance functions whilst the car is moving. To prevent this, a standard
governing vehicle displays is needed to ensure a good user interface with the
driver which is not distracting or confusing.
For both public and private organizations involved in procuring ITS
equipment, there are compelling reasons for adopting voluntary standards
wherever possible:
where ITS products and services have been designed using established
standards, users can source a range of competitive suppliers before deciding on
their purchasing options. This avoids lock-in to a single supplier and ensures
that standardized components are interchangeable;
18
ITS standards support system interoperability and integration. For
example, a vehicle using a single transponder can access a range of ITS user
services based on standardized equipment and communications – such as toll
payments, in-car signage and international border crossings.
The perspective of suppliers is less clear-cut. Depending on their market
position, private companies may – or may not – be motivated to participate in
standards setting by consensus. Common standards can lead to economies of
scale in production – and open up sales to a wider market. Companies in
dominant market positions are usually reluctant to move away from the defacto standards of their own products – unless they are convinced that the
establishment of new consensus standards would help them access a much
larger market.
In general, private companies whose business is globally oriented, are
interested in consensus standards and global agreement on standards – to
secure economies of scale in manufacturing and marketing their products.
These standards also reduce their risk of investing in new products and
services that may have limited market potential – or could soon become
obsolete.
The word “standard” is often misunderstood and misused. A dictionary
definition of standard may refer to “a level of quality or attainment” or “falling
within an accepted range”.
The official International Standards Organization (ISO) definition of
a Technology Standard is “a document that provides requirements,
specifications, guidelines or characteristics that can be used consistently to
ensure that materials, products, processes and services are fit for their
purpose.”
Developing and adopting voluntary standards provides many benefits:
interoperability – ITS standards support system interoperability and
integration. For example, a vehicle can use a single transponder to access
a range of ITS user services – such as toll payments, in-car signage,
international border crossings – across a number of different jurisdictions;
safety – standards provide a tool to enforce common agreement on
what is, and what is not, safe. For example, standards aimed at reducing driver
distraction can be used to ensure that complicated in-vehicle multi-media
functions are not accessible to the driver while the car is moving;
19
market development – common standards provide reductions in costs
because of economies of scale in production – and facilitate sales to a wider
market;
procurement flexibility – ITS products and services based on
standards, allow buyers to decide on their purchasing options after considering
a range of competitive providers – so avoiding lock-in to a single supplier.
Standards can be categorized in various ways according to different
perspectives that are not mutually exclusive.
Technical perspective. ITS rely on communications supplied by
telecommunications operators offering a variety of hardware and
communications media – to provide the platform for ITS applications.
Examples include, fiber optics, the internet, WiFi, 3rd and 4th generation
cellular phone networks together with computer servers and devices. The
hardware and communications are hosts for the ITS applications and handle
the physical movement of data and information.
ITS technical standards are concerned with how communications are
adapted for a specific application – standardizing specialized ITS data content
and governing communications interfaces. These include protocols and
message sets which enable smooth data flow and information exchange among
components and subsystems:
protocols, such as TCP/IP for the Internet, specify the structure for
transmission of data messages and the details of message formats, and describe
how to handle error conditions;
message sets (multiple messages and data sets), usually defined in
a data dictionaries (a standardized format that allows meaningful exchange of
information between subsystems). For example, for information exchange
related to incidents – standards are needed to code a certain number of message
elements that will describe unambiguously the location (such as the road
segment number) and the type of incident (fire, injury).
There are some cases where ITS-specific communications standards
have been developed – most notably in electronic tolling and other vehicle-toroadside technologies. In this case, the standardization of frequencies and
modulation techniques ensures that communications hardware and software
interoperate correctly.
20
Geographical perspective. ITS standards can also be categorized by
their geographic scope – according to whether they have been established at
the local, regional, national, international or global level. Not all standards
need to be global. For instance, for practical reasons, most ITS applications
developed for commercial vehicle operations need only be capable of
operating at the continental level (such as within China, Europe, North
America). Global ITS standards for commercial vehicle operations are not
feasible at the moment – and they are not essential, so long as heavy goods
vehicles/lorries do not operate in more than a single continent. By contrast,
cargo identification systems need to be compatible across modes of transport
and must meet global standards – if they are to be capable of following freight
movements between continents and ensure proper security checks along the
way.
Development perspective. ITS standards can also be categorized
according to the nature of the agreement – by which they become established
as standards. ITS standards may be:
de facto standards – established by a dominant manufacturer/supplier
and achieving market acceptance through commercial success;
consensus standards – developed through formal procedures in
official standard development organizations – or emerging from unofficial
industry collaboration to agree on standards outside the official bodies and
their formal processes;
regulated standards – established by governments (in the form of
a regulation), either because other methods have been unsuccessful or because
they need to be interoperable across borders.
Regulation can also be used to accelerate and harmonies deployment of
ITS. An example of this approach is the European Commission’s ‘ITS
Directive’. (See http://ec.europa.eu/transport/themes/its/road/action_plan/) It
mandates that new ITS deployments in the EU comply with standards
specified under the Directive – in four priority areas:
optimal use of road, traffic and travel data;
continuity of traffic and freight management ITS services;
ITS road safety and security applications;
linking the vehicle with transport infrastructure.
Соседние файлы в предмете [НЕСОРТИРОВАННОЕ]