SIMPLAN model

Urban modelling for enhancing master plan making: SIMplified PLANning modelling suite for Ahmedabad

An urban planning policy usually has two key components: the urban form and the transport system. There can be a variety of theoretical possibilities of these two components and also how they can be combined. Some typical urban forms and transport policies and their combinations are shown schematically in the figure.

Planners are usually faced with the decision of what planning policy to pursue in order to achieve the best possible future! Using models that simulate urban dynamics, it is possible to test and assess alternative planning policies, thereby making the decision process more objective and transparent. Examples are the full-fledged and complex land use—transport interaction models, which have been successfully applied in many cities of the developed world, demonstrating its effective use in assessing alternative planning and transport policies before finalising their master plan. However, in the developing world, building such complex models is challenging due to lack of data availability and resource constraints. Addressing such constraints, a SIMplified PLANning modelling suite called SIMPLAN has been developed for the case study city of Ahmedabad, India. SIMPLAN is built using available census and some basic employment related sample survey data, and contains four sub-modules for spatial trend analysis, residential location, modal split, and alternative policy assessment framework. SIMPLAN development is an attempt to build simplified yet robust analytical tools in the context of developing countries.

The four SIMPLAN modules are:

    • Trend Analysis Module (TAM): a set of tools for analysing the evolution of the spatial structure of a city (for more details see Adhvaryu, 2011b)

    • Residential Location Module (RLM): an econometric residential location model that uses average housing rents as part of the generalised cost in a gravity-type allocation function and currently deals with work trips. RLM estimates population distribution, by socioeconomic groups, as a function of employment location and residential floorspace (for more details see Adhvaryu & Echenique, 2012)

    • Modal Split Module (MSM): a multinomial logit model to estimate the proportion of person work trips by different modes generated by the RLM (for more details see Adhvaryu & Echenique, 2012)

    • Assessment Module (ASM): After calibration, SIMPLAN can be used to assess alternative planning policies for a future/horizon year, with appropriate employment, dwelling floorspace, and transport inputs. The key assessment criteria in are economic (consumer surplus in housing and transport), environmental (new land required and CO2 emissions), and social (distribution of economic benefits and mix of socioeconomic groups) (for more details see Adhvaryu, 2010).

The main land use inputs to SIMPLAN are employment and dwelling floorspace by zones and transports inputs are average network distances and speed by mode. For Ahmedabad, three alternative policies for 2021 were tested: trend policy (business as usual), compaction policy and dispersal policy, with appropriate combinations of land use and transport inputs.

The main advantages of using this type of approach are:

    • It allows planners to prepare policy alternatives with drastic variations and test these to see its effects in the future, enabling them to make more informed decisions for before arriving at the ‘most suitable’ policy to be pursued in the development / master plan (popularly known as DP).

    • Outputs from the model are disaggregated by zones and therefore dovetail well with the next spatial level of planning, ie the town planning scheme (TPS).

    • Quite importantly, since the model is spreadsheet based, it is simple to understand and run. All model runs can be out in-house by city planning officials on their PCs or laptops! This avoids the ‘black box’ approach usually prevalent in planning projects involving mathematical modelling, wherein specific tasks are outsourced to private consulting firms.

The polices tested for case study city of Ahmedabad for year 2021 include: [1] compact city with high quality public transport [2] dispersed development with significant road capacity enhancement, and [3] trend policy, denoting a business as usual scenario in terms of supply of residential floorspace, development control regulations (DCRs), and public transport development (which acts as a reference policy to compare the policies developed by 'design'). Sensitivity analysis is also done to see the effects of change in distribution of jobs.

The critical review of the Ahmedabad Development Plan making approach (as in the Ahmedabad Development Plan for 2011) is discussed in Adhvaryu (2011a), establishing a need for model-based plan-making approach.

Key SIMPLAN outputs (for Ahmedabad) indicate that dispersing cities proves to be economically beneficial to society as a whole, because households would tend to gain from the lower rents further afield. Compaction policy performs better in terms of environmental aspects such as consumption of new land for development and vehicular emissions, but bearing in mind traffic congestion is currently not modelled, which could potentially reduce this advantage. With regard to social aspects, it appears that any deviation from the trend creates a lopsided social mix, although compaction policy is a bit better than dispersal.

As mentioned above, SIMPLAN is developed in a spreadsheet environment, with all key operations controlled by a visual interface using sub-routines written in Visual Basic Application code. This creates a user-friendly graphical interface that makes the model simple to understand and operate by local planning agencies, and, in addition, provides them with the flexibility of updating the model as and when new data is available or a new round of census is conducted.

India is rapidly urbanising and is at a crucial juncture in its development. The urbanisation phenomenon has both positive and negative effects. It could be argued that appropriate urban development policies and planning methodology can use the potential positives to foster better equity of benefits from the booming overall growth. On the other hand, if India does not capitalise on the potential advantages appropriately, then in the next few decades the negatives of urbanisation could amplify, worsening city living and become a stumbling block in its economic growth story. It is believed that using a methodological planning framework such as SIMPLAN, cities in the developing world can prepare their own tailor-made policy that best satisfies their objectives, making the planning efforts count for improving the quality of life in cities.

A succinct overview of the SIMPLAN simulation modelling framework is discussed in Adhvaryu (2012).

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