SPM analysis modules produce a wide range of inter-related metrics that allow for robust and meaningful comparisons of alternative land use and transportation scenarios. Once changes are made to the base canvas via painting or translation of existing plan, scenario core processes combine the changes or growth input with the existing conditions to create future scenarios and estimate developable land and demographic characteristics.
These scenarios then run through the model engines briefly described below to measure their performance for mobility, air quality, public health, fiscal impacts, resource consumptions, and others.
Land Consumption engine calculates greenfield land consumed to accommodate new growth for future scenarios. Greenfield is identified based on the assessment of the base year or existing condition. Total land consumed in the existing greenfield is then estimated by applying per unit or per employee assumptions, accounting for housing type as well as employment sector.
Fiscal Impact Engine estimates the impacts of varying forms of development on local expenditures. The current engine limits its focus to the impacts associated with new residential growth, accounting for the capital costs of new and upgraded local infrastructure, and operations and maintenance (O&M) costs to serve new and upgraded infrastructures. Cost factors vary by Land Development Category (LDC), development condition (refill or greenfield), and housing type (single family detached large lot, single family detached small lot, single family attached or multifamily).
Building Energy Engine calculates residential and commercial building energy use, and their related costs and greenhouse gas (GHG) emissions, for both new and existing buildings. Within the engine, energy use is determined by three types of variables: building characteristics, climate zone, and efficiency factors. Building characteristics and climate zone determine what baseline per-residential unit or per-commercial square foot factors are used to calculate energy use. Reductions are then applied to the resulting baseline estimates to reflect the implementation of building efficiency and conservation policies into the future.
Water Engine calculates indoor and outdoor residential and commercial water use, and their related costs and greenhouse gas (GHG) emissions, for both new and existing buildings. Indoor and outdoor water use is first calculated according to baseline rates, determined by building or employment characteristics and climate zone, and then adjusted to account for the application of efficiency and conservation policies into the future.
SPM incorporates a comprehensive “sketch” travel model that produces vehicle miles traveled (VMT), mode choice, and congestion estimates for land use and transportation scenarios, as well as transportation-related costs, greenhouse gas (GHG) emissions, and pollutant emissions. Transportation analysis capabilities within SPM are currently based on the Mixed-Use Development (MXD) trip generation model that estimates the likely degree to which a development area’s traffic generation will be reduced due to trip internalization, external walking, or transit trips. The MXD method uses land use and demographic information as well as outputs from regional transportation model to calculate trip reductions, resulting from the specific combination of factors known to be most influential in trip generation.
Public health engine measures the impact of land use patterns and urban form on physical activity-related weight and disease incidences, and respiratory impacts, as well as their related costs. Respiratory health analysis is based on overall VMT from SCAG’s regional transportation model and associated criteria air pollutant emissions from EMFAC. Health incidence and valuation assumptions for select air pollutants (PM2.5, Sox, VOC and NOx) are then applied to estimate pollution-related health incidences and costs.
Physical-activity related health incidences are calculated from California Public Health Assessment Model (C-PHAM) that uses a behavioral and exposure-based pathway approach that links the built environment with health outcomes. C-PHAM provided health outcomes include the Body Mass Index (BMI), the likelihood of being obese or having high blood pressure/heart disease/type 2 diabetes by age group.
SPM incorporates the Nature Conservancy’s land conservation engine that measures the impacts of change upon a detailed depiction of existing conditions on the four major themes: carbon, water, agriculture, and habitat. The terrestrial carbon storage model analyzes the impact of land use changes on carbon storage associated with natural vegetation in the landscape as well as with soil organic carbon. The water theme measures the impacts of changes to natural lands or land cover on watershed, the ground recharge potential of converted lands, water resource priority areas, and agricultural land with associated water demand. The terrestrial habitat model measures the capacity of the landscape to facilitate or inhibit species movement and the suitability of land use in an area to support terrestrial vertebrates. The agricultural model estimates the impact of land conversion on agricultural production and capacity.