This collaborative project is being funded by the Department of Environment, Transport and the Regions as part of the UTMC Programme. It is tackling the UTMC01 task: Selective Vehicle Priority. The project started in March 1998 and is due to be completed within twenty four months.
The project title, Selective Vehicle Priority in the UTMC Environment,
(SPRUCE) expresses the chief objective; to research the principles of selective
vehicle priority within the UTMC systems architecture environment and to
develop an application. In keeping with the terms of reference, a
top down approach will be employed, starting with a study of the current
state of the art in signal network priority systems, and an examination
of the wide range of needs within the market that such systems must address.
In the subsequent development of an application, the general UTMC goal
to maximise user take-up will be pursued by ensuring that it fulfils the
needs of a sizeable sector of the market and that it is compatible with
the requirements of existing users to enhance their legacy systems through
migration. Our aim therefore is to produce and trial a commercially
viable product that can be supplied and supported after the end of the
UTMC research project.
Most development of UTMC based bus priority utilising selective vehicle detection within the UK, has been SCOOT-based resulting in the facilities now available in version 3.1 of the software. Some work, based on the principles of bus priority within SCOOT, has been undertaken for the London fixed time systems (SPRINT). Whilst UK developments to-date have been successful, it is likely that there are opportunities to improve on the performance of current systems by studying the international state of the art in this area.
Facilities to give priority to other modes such as emergency vehicles do exist, but they are crude, do not make use of selective vehicle detection and are less well developed than priority strategies for buses. Furthermore, there remain areas of the UTMC market with no facilities developed specifically for them, such as fixed time systems outside London, and LRT systems.
The assessment of research and current developments will identify opportunities to expand and improve priority strategies currently available for UTMC systems within the UK. In parallel with this activity, an assessment of user needs will identify the unfulfilled gaps in the market. The potential for fulfilling market needs either through the products of existing research or by the development of new strategies will be estimated.
Some opportunities for enhanced performance are highlighted in the terms
of reference for this project, and they include;
Other examples of enhancements could include;
Analysis of current systems and research will be underpinned by the
significant collective experience of the partners which includes;
The assessment of user, institutional and organisational needs will
be undertaken on both a national level through surveys and forums, and
at a level local to the areas for the proposed trials in Leeds and Sheffield.
Detailed case studies will be made of the circumstances and requirements
of the trial areas, allowing specific objectives to be addressed by the
trial application.
The strategy requirements for the application to be developed on the
project will be defined in terms of;
The system will provide priority within both a fixed time UTMC environment
and a dynamic UTMC environment. The project will build on the significant
development and trialing work that has taken place on existing UTMC strategies
by adopting one, BALANCE, as the vehicle for fulfilling the requirements
determined for the application. Fixed time control is an option within
the BALANCE strategy. Where necessary the strategies within the current
version of BALANCE and user programmability will be augmented through software
development.
Logical and physical architecture models for the SVD priority application will be developed within the framework of the UTMC specification. The analysis will consider both general principles applicable regardless of the details of the mechanism for priority proposed, and any specific constraints on architecture posed by the application to be developed for the trial.
The trial application itself will be designed to demonstrate firstly the benefits of performance and flexibility that can be achieved through the UTMC format using a fully compliant configuration, and secondly the integration of modules from a mix of suppliers made possible by the open format of the UTMC interfaces. The proposed application will therefore be developed and tested in two architectural configurations; a fully UTMC compliant system and a migration configuration. The fully compliant system will be a development of Microsense's hierarchical implementation of BALANCE, which has local processing of tactical optimisation (MICRO-BALANCE) combined with centralised processing of strategic decisions (MACRO-BALANCE). The existing BALANCE architecture will be adapted to conform to the UTMC data transfer and interface requirements.
The second architecture will consist of BALANCE in a centralised form
providing fixed time control through the newly upgraded PEEK host system
shortly to be commissioned in Leeds. Some UTMC facilities and interfaces
are already incorporated in the host specification facilitating the addition
of the proposed strategy.
Application development will entail the modification of the implementation
of BALANCE already developed by Microsense. The BALANCE strategy
software will be developed by the addition of modules to provide additional
functionality and flexibility. The public interfaces for communicating
data between separate hardware modules will be developed in keeping with
the chosen architecture options and the current and emerging UTMC specification.
After development, the SVD priority strategy software, a derivative of BALANCE, will be laboratory tested and tuned by linking it to a micro-simulation traffic model (DRACULA) of the proposed trial networks. The evaluation criteria for the laboratory tests will be set by the objectives for priority determined for the trial networks during the case studies.
The laboratory tests will give predictions of the performance
of the chosen SVD priority strategies and will allow sub options to be
tested. The tests will also be used to evaluate the strategy performance
over a wider range of conditions such as traffic flows or SVD frequencies,
than will be possible during the street trial. Facilities that are
not feasible for street trial, but may enhance performance or provide priority
for classes of vehicle other than public service vehicles can also be tested.
Street trials will be performed on networks that demonstrate a range
of conditions and requirements for priority. The priority vehicles will
be regular buses, guided buses and light rail vehicles. Levels of
traffic congestion, frequency of PSVs and spacing of stops vary widely
in the networks selected.
Guided Bus network, heavily congested strategic interchange, urban and sub-urban radials. Bus gates on guided bus corridor. Fixed time UTMC appropriate in tightly constrained network where traffic speeds are high. Street equipment required will be TIRIS readers and selected congestion detection.
All buses using the test area to be equipped with passive transponders
for the trial. It is envisaged that a proportion (say guided bus
only) will have intelligent transponders linked to the wayfarer ticketing
system. Legacy data transmission system will demonstrate what can
be achieved within the constraints of migration.
LRT system: vehicles are already equipped with intelligent transponders. Full implementation of SPRUCE will require installation of MICRO-BALANCE outstations, and new data communications.
A performance evaluation will be undertaken using criteria determined by the objectives set by the case studies. Surveys of general vehicle flows, and delays and priority vehicle journey times will be undertaken. The surveys will be analysed to validate the conclusions derived in the laboratory tests.
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