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Using SGI to Evaluate Transit Oriented Development: Wilmington Area Metropolitan Planning
Note: EPA no longer updates this information, but it may be useful as a reference or resource.
Smart Growth Index (SGI) was used to assess the benefits of a Transit Oriented Development (TOD) for Edgemoor, Delaware, a community in the Wilmington Metropolitan Area. The proposal is for the redevelopment of Merchant's Square, an abandoned shopping center, that is currently a blighted and underutilized property. The size and location of the site give it the potential to become an effective TOD, and serve as both an economic and public transit hub for the community.
A TOD is a mix of land uses, residential, office, shopping, civic uses, and entertainment, within easy walking distance of a transit station. Compared to current development trends, TODs can protect water and air resources and reduce impacts on the land. The close proximity of land uses and transit decreases people's dependence on driving for access to shopping, services, jobs, and recreation by giving them the choice of utilizing other forms of transportation. These transportation options can help lower air emissions. TODs can also benefit regional water quality by concentrating development and reusing previously developed land - thereby reducing development pressure on open space. Reuse of previously developed land often means accommodating new development with out any increase in impervious surface or runoff.
SGI was used to evaluate three different land use and transportation scenarios for the site, each focusing on the redevelopment of Merchant's Square but with different transportation improvements:
- Scenario 1: A full rehabilitation of Merchant's Square, and local transportation improvements that are limited to the completion of the sidewalk network within the project site. This scenario is expected to produce 1,250 new jobs on site.
- Scenario 2: All the improvements of scenario 1, plus the renovation of 85 apartments adjacent to a current apartment complex, and the construction of 58 additional townhouses. No additional transportation changes would be made.
- Scenario 3: All the improvements of scenarios 1 and 2, plus the additional transit improvements needed for the site to contain all the parts of a successful TOD. This scenario includes the Fox Point Train Station adjacent to Merchant's Square and three new bus stops serving the train station and the shopping center.
The site was evaluated on the three-redevelopment scenarios based on land use, housing, employment, transportation and environmental indicators
Results:
| Key Indicators | Current Conditions vs. TOD #3 |
|---|---|
| Population density (population/sq. mi.) | 26.90% |
| Jobs/housed workers ratio | 462.70% |
| Land-use diversity | 317.40% |
| Residential density (dwellings/acre) | 0.10% |
| Multi-family housing share | -0.60% |
| Housing proximity to transit (avg. ft.) | -2.20% |
| Employment density (employees/acre) | 421.60% |
| Employment proximity to transit (avg. ft) | -39.20% |
| Sidewalk completeness (percent) | 210.30% |
| Walkability index (Pedestrian Route Directness) | 21.00% |
| Vehicle miles travel (per capita) | -18.50% |
| Vehicle trips (per capita) | -20.00% |
| Carbon monoxide (CO) (lbs/yr/capita) | -18.40% |
| Hydrocarbon (HC) (lbs/yr/capita) | -18.50% |
| Oxides of nitrogen (NOX) (lbs/yr/capita) | -14.10% |
| Carbon dioxide (CO2) (lbs/yr/capita) | -11.80% |
SGI analysis showed that the existing conditions at the site contain population densities, mixes of residential types, and housing proximity to transit to support some transit services, but also show that the viability for transit increases significantly for the three-redevelopment scenarios when compared with the current conditions.
The table above highlights the percentage difference in the listed indicators between current conditions and scenario 3 - the option with the greatest amount of TOD elements.
- The balance between jobs and housing showed a 463 percent increase, thus allowing an increased probability of trips made by means other than automobile.
- The average distance of homes and employment to transit decreased by 2.2 percent and 39.2 percent respectively The walkability index, or ease of walking to key amenities, increased 21 percent in large part due to the sidewalk completeness increasing over 68 percent.
- Scenario 3 showed a 20 percent decrease in vehicle trips and an 18.5 percent decrease in vehicle miles traveled. This decrease in automobile usage would result in an 18.4 percent reduction in carbon monoxide (CO) emissions, an 18.5 percent decrease in hydrocarbon (HC) emissions, and a 14.1 percent decrease in the emission of oxides of nitrogen (NOX).