TRAFFIC management | 89
Supersize me
How transport modelling tools in Montreal have evolved in response to
the Canadian city’s growing need for a congestion management solution
Words | Francine Leduc & Christian Letarte, City of Montreal, Quebec, Canada
This is the story of the City of Montreal’s
modelling group (EMViM) and its search
for an all-in-one, extensible modelling
environment that would not only allow it to
streamline its simulation platform but also
expand the Montreal model two or three
times beyond the size of the original.
When the modelling group started
out in 2004, the only tool available was a
regional macroscopic model developed by
the Ministry of Transportation of Quebec
(MTQ). This was useful for estimating the
long-term evolution of patterns, though it
lacked the refinement to compare localised,
time-dependent traffic impact between
scenarios. From a sub-network of that model,
EMViM went on to build a dynamic city
model, Modym, by acquiring a more refined
mesoscopic tool that could show congestion
and queuing. It later supplemented this
mesoscopic tool with several microscopic
packages for analysing areas of more
complex interaction such as projects
involving analysis of pedestrian crossings or
preferential transit measures.
It rapidly became clear that the
combination of mesoscopic and microscopic
simulation tools was best for analysing
different schemes and graphically illustrating
the consequences of capacity increases or
reductions. The natural evolution therefore
was to seek a tool that could easily combine
both these levels and have good integration
with strategic planning tools, to answer
Montreal’s growing need for congestion
management planning.
The lay of the land
With a population of 1.9 million inhabitants
(25% of the entire population of Quebec),
Montreal is one of the most populous islands
in the world, outranking even Manhattan
Island in New York City. Add this to
Montreal’s suburbs and its relative proximity
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90 | TRAFFIC management
Project
updates
on MODUM and
GNSSMeter, plus
much more!
Perso
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Modelling is helping an already strained network face its future
TSS’s Aimsun 7 hybrid simulator – a mesoscopic model showing a microscopic pocket of greater detail
to cities such as Ottawa and Boston, and it is
not surprising that the crossings that connect
the island to its surroundings are heavily
congested: the Champlain Bridge and the
Jacques Cartier Bridge together handle a
staggering 101 million vehicles a year.
Once on the island, there are 5,626km
of road and 2,434 signalised intersections
with a highly urbanised city centre and a
dense CBD hemmed in by the river on one
side and the Mount-Royal escarpment on
the other. In the evening this area becomes
gridlocked with vehicles trapped in the
centre struggling to exit.
Putting further pressure on an already
strained situation, many major road
infrastructures are scheduled for renovation
over the next few years and the improvement
of clogged arterial and collector roads
will have a big impact on road capacity.
Among these challenging projects are the
roadworks planned on the A40 (a central
freeway that runs along the long axis of
the island), the Turcot interchange and
Champlain bridge replacements – three
multi-billion dollar projects at the busiest
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points of the road network. The city is keen
to minimise traffic flow disruption from these
building projects, particularly as congestion
is already a key issue in citizens’ minds.
It is clear that, in addition to planning
applications (modelling steady-state
behaviour under recurring conditions),
operational assessment will be a top priority.
Operations models look at short-term
capacity and demand signals at isolated
incidents such as accidents or short-term
lane closures, which will be more relevant
than ever when the aforementioned
construction projects get under way. For
the City of Montreal, software that can
combine both planning applications
and operations modelling will become
a necessity for managing these roadworks
and minimising traffic congestion.
A better toolbox
EMViM considered many tools and
combinations of tools for the expansion of
the dynamic Montreal model, but there was
only one on the market that offered all three
levels of modelling inside one software
Montreal before and after: the smaller model
and the new, much larger one
application – microscopic, mesoscopic
and macroscopic with a singular network
representation and underlying database. As
the icing on the cake, the micro-meso hybrid
capabilities of TSS’s newly released Version
7 will allow EMViM to overcome mesoscopic
restraints, particularly on freeway merge and
diverge sections and connections to arterial
networks, where modellers can simply zoom
in for greater granularity. In the original model, these mesomicro shifts involved tedious and error-prone manual
interchanges of data between packages using different
networks and databases, followed by hours of troubleshooting.
As well as avoiding mistakes and reducing effort, an integrated
tool increases the efficiency of operations models. It is not
recommended to be modelling in meso and putting out
individual fires with separate micro packages.
Another intangible lies in the effect of integrated software on
the high cost and management burden of using several different
software tools. In the past, four or more different types of software
needed to be maintained, a situation that had become both
technically and administratively challenging. This streamlining is
closely related to the important issue of the retention of expertise:
turnover of personnel is less of an issue when only one or two
software tools are involved as opposed to four or five. This is of
special interest to public agencies or large consultancies that
consider modelling know-how to be a core competence.
But the most important factor in the choice of modelling
tool was scale. EMViM needed large network capabilities – an
extensible mesoscopic model many times larger than its current
version that could cover the entire island of Montreal and keep
on growing. The storage requirements associated with
representing large networks can easily exceed the 4GBs
imposed by 32-bit architectures, leading to the necessity of
64-bit architecture as well as multi-threading capabilities.
Crucially, EMViM did not have to take a leap of faith on this
point as the software of choice has already proven itself more
than capable of handling a very large model in the Greater
Toronto Area for the Ministry of Transportation of Ontario (MTO).
EMViM was inspired by what the MTO achieved with its
Aimsun simulation framework: providing an analytical tool
for future traffic planning, operational reviews and strategic
traffic management decision making; potentially, a version
of integrated corridor management.
The modelling group is currently in the process of converting
its GIS networks and is not yet even close to a calibrated model
of the island. However, EMViM is always looking ahead and future
plans include modelling transit demand and the extension of
mesoscopic modelling across the rivers; and eventually over the
entire region in association with MTQ. Montreal is thinking big. n
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