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Mesoscopic Modelling

Mesoscopic modelling allows a level of detail greater than a strategic model. All software houses recognised the need for a software package that sits between strategic and micro-simulation modelling capability. INRO was the first to put its Dynameq software package on the world market and is now the most mature. Users of the newer mesoscopic modelling packages are ironing out software bugs that have long been solved in Dynameq. Transport Modelling has been using the Dynameq software for the last seven years with very pleasing results.

Dynameq is a True Mesoscopic Model
Dynameq is a true mesoscopic model as it uses equilibrium as well as the other algorithms used in micro-simulation models such as car following, gap-acceptance and weaving.

Chart showing where the mesoscopic package Dynameq fits into the modelling world. It has both equilibrium (parallel paths) and individual car mathematics.


Flowchart

In NSW the Roads and Maritime Service (RMS) preferred software is Paramics followed by the VISSIM microscopic software packages. The traffic models produced with these software packages do not have equilibrium which means that if the network contains parallel paths, the traffic is only able to use an alternative path if it has been ‘hard wired’ into the model and therefore limiting its applications.

Details that Dynameq models may include and are generally not found in a Strategic model

  • zones that are typically city block size.
  • major exit and entry centroid connector links are more accurately located within the city block. This is most obvious in car parks where the entry point may be different from the exit.
  • traffic generators such as libraries and community centres are coded in.
  • time slices of the travel demand reflecting localised traffic related activities, such as school starting/finishing times and shop opening/closing times. For example once school has started the traffic is seen to decrease in that location.
  • time-based changes such as the parking restrictions during peak hour, and reduced speed limits around academic institutions. Both of these measures alter the most attractive paths through the network.
  • T2 and T3 lanes are coded in.

Dynameq can be used to study:

  • congestion relief strategies
  • corridor and land use management
  • construction mitigation e.g. what path can be taken when a lane has to be closed
  • transit (public transport) design
  • emissions modelling

Parallel Paths

Dynameq’s ability to automatically find parallel paths is shown in the next three plots.

Plot 1: This is a Dynameq plot for the Parramatta Charles Street extension study. This shows the paths taken when the network is not fully loaded.

Plot 1

Plot 2: Paths taken when the network is almost fully loaded.

Plot 2

Plot 3: Paths taken when the network is fully loaded.

Plot 3

Refer below ‘Modelling the Parramatta CBD’, for more details.

Some Examples of Transport Modelling’s use of Dynameq are:

Modelling the Charlestown Shopping Town CBD including Bus Priority Schemes

Charlestown Shopping town is the largest shopping centre in the Local Government Areas of Newcastle and Lake Macquarie. Developers had prepared plans to double the capacity of Charlestown Shopping Town, and Lake Macquarie Council wished for all the developments to be integrated. The shopping complex is bounded by the intersection of the Pacific Highway and Charlestown Road. There are developments on both sides of the Pacific Highway.

The developers had created a very elaborate model of the proposed shopping complex in the Paramics software. Lake Macquarie Council approached Transport Modelling to develop a simple model to independently verify the modelled results from the developers.

Figure 1: Dynameq comparison plots showing the Lane Occupancy with and without the proposed expansion.

Plot 3

The modelling challenge here was the Pacific Highway. It runs north-south through the developments. Given that this movement was the major planning consideration, Transport Planning considered the possible alternative paths for the traffic. This determined the rather larger than expected study area and included the Charlestown bypass which is not shown on the image above. When the various options for the Pacific Highway and the parallel paths were tested, it was found that the bigger study area proved necessary.

The Dynameq modelling showed encouraging results. Some of the future paths taken correlated to the concerns that existing residents had expressed about traffic increases in their local streets. Concerns were warranted especially when bus priority schemes were developed to encourage use of the planned bus interchange. These schemes would mean that some of the capacity from the Pacific Highway (due to bus priority lanes) would be taken out resulting in some traffic moving onto the bypass, and some other traffic would use rat runs through the local streets.

External auditors reviewed both the Paramics and Dynameq modelled results. They concluded that the results generated by the Dynameq software with its parallel paths produced more believable results than the Paramics model which had a very narrow study area.

The Dynameq model was used to develop the Charlestown Master Plan.

Modelling the Maitland CBD including the Southern Bypass

Maitland is a major in-land city centre in the Hunter Region. The Hunter River borders the CBD. Because the City centre has been in decline for some time, Maitland City Council approached a team of specialists to assist them with developing a plan to revitalise the CBD and hence its economy. Transport Modelling was part of this team and it was tasked to develop a model that could be used to explore a CBD Southern Bypass, test various options for the opening of the City Mall and test the planners’ version of a revitalised CBD.

The planners required a model that was sensitive enough to test

  • various options for opening the Mall (westbound only, eastbound only, two way, and car/pedestrian mix) and
  • land use options within the heart of the CBD to create a more open and friendly CBD.

The modelling challenge of this study was the derivation of the travel demand matrix (trip tables). Because of the location’s geography (the Hunter River in the north and the New England Highway and the railway line in the South of the study area) there were only three locations where the external traffic could enter or leave the study area. When these traffic counts were analysed, it was possible to separate the through-flows from the localised flows. These flows were found to have different peaks. On reflection this made sense, the through-flow peak had to be earlier because their trip destinations were in employment centres in the surrounding areas.

The planners within the team were very impressed with the model’s capability and it was used extensively to derive a preferred outcome for a revitalised city. Council recently announced that the Mall will be opened.

Figure 2: Dynameq plot showing the Lane Occupancy without the opening of the Mall.

Figure 2

Figure 3: Dynameq plot showing the queues on Maitland Bridge and on the right the report front cover photograph displaying these queues.

Figure 3
Modelling the Tallawarra Lands including Development Option Planning

Tallawarra Lands is the 535 hectare site adjunct to the Tallawarra power station in the Wollongong Local Government Area south of Sydney. The developers wanted to test options for both the internal traffic and traffic entering and exiting the site.

Transport Modelling developed a model that extended beyond the immediate site and included the surrounding road network, extensive enough for the Tallawarra traffic to disperse.

The network was cut out of the TRACKS software model that covered the Wollongong and Shellharbour Local Government Areas strategic network. It was found that the existing traffic conditions could be modelled well in Dynameq, but that the future traffic demand could not be accommodated on the future road network and this lead to some tension as the strategic modellers believed that their future networks were correct. Sometime later, Transport Modelling was working on another project for the NSW government that involved integrating that TRACKS strategic network into the Sydney Strategic Network. During that work, it was resolved that those future TRACKS networks lacked much needed capacity.

Bus Priority Scheme - Macquarie Centre Queue Jump Demonstration Project

In Sydney there are about nine regional Centres in which buses will have to take on a more prominent role because the roads accessing these centres have limited capacity, and one possibility is to give buses a higher priority entering these centres. The task was to develop a model to test the bus queue jump scheme.

The Macquarie Centre area was selected for its high bus movements. A bus queue jump was coded into the Dynameq network, and the benefits evaluated.

Testing six second queue jump for buses. The yellow lines show the transit only intersection movements. These are very easily coded into Dynameq.

Testing six second queue jump for buses

Figure 4: This plot shows the 6 second phase for the bus queue jump. This is easily coded into the Dynameq model.

Figure 4

The results showed:

  • a slight increase in the Vehicle Hours Travelled (VHT) and Vehicle Kilometres Travelled (VKT). This is expected due to the 6 seconds additional cycle time.
  • bus travel time reduced slightly, but this was not statistically significant, and
  • the standard deviation of the bus travel times reduced very dramatically which made the bus queue jump especially desirable. A very significant finding indeed.
Modelling the Parramatta CBD – Charles St Opening

Dynameq software was used to develop and build the micro-simulation model for the Parramatta CBD. This work is described in a paper: ‘Capturing Public Transport Benefits of Alleviated Road Congestion’ by David Kilsby & Paul van den Bos. This model was used to study the Charles St Opening which would effectively become a city centre bypass.

Plot 4: This image of the Parramatta network shows how the north-south movement can block the east-west movement. The red lines indicate queues.

Plot 4
Lochinvar Land Release Study

The Lochinvar study area is a greenfield. The planners were exploring the options for the staging of the land release program.

The traffic modelling was designed to assist the planners and engineers with resolving traffic related issues of the connections with the New England Highway which runs east-west through the area. Equally important was the issue of the internal north-south connections across the Highway.

Figure 6: Dynameq plot showing Link Occupancy for the Lochinvar study.

Figure 6
Medowie Study

Medowie is a small community of 7,000 people, planned to grow to 15,000. The Medowie study explored options for the internal network with the aim of keeping the characteristics of the old township.

Figure 7: Link Occupancy for the Medowie study.

Figure 7
Safety Measures

Refer to GUI and Training – Wagga Wagga Traffic Model.

A median treatment of the Sturt Highway through Wagga Wagga was studied to improve:

  • efficiency of the Highway and
  • safety at the Base Hospital which fronts the Highway.

Plot 5: Dynameq can be used to indicate how accident rate could be reduced through fewer lane changes. This plot shows the Wagga Wagga median Treatment in front of the Base Hospital.

Plot 5

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