Smart growth is a set of principles that allow more compact and mixed development, create sustainable mobility as core services reducing urban sprawl, parking demand and vehicle pollutions, and maximize effectiveness of investment. Smart growth often confused with ‘density’ as bad development, causes angst with local communities and local government. The reality is when done well, with ‘appropriate’ density and mix, development can result in several economic, environmental and social benefits. Limits of appropriate density varies with area context. In-depth analysis using Toronto data (within 500m of subway stations) reveals benefits of density diminish beyond a “density sweet spot”. While the minimum subway density threshold is considered 100 population and employment per hectare, optimum transit share (between 40% to 50%) is achieved when density is around 200 to 450, with downtown core exceeding 450 and a marginal increase in transit mode share. While employment is key ingredient of maximum transit usage, appropriate share of diverse land-uses (between 25% to 40%) is critical to providing access to daily needs. To the contrary, the majority of low-performing subway stations (around 58%) indicate that vehicle focus retail or employment usage, poor physical connectivity, pointed to density around rapid transit stations and lack of real time information. Optimum limits of density also determine emission outcome. Total on-road CO2 increases rapidly with population density below 1,650 persons per square kilometer while per capita emissions decline as density rises (1,250–3,500) and emissions begin to rise again as density exceeds 4,000. These boundaries set the limits of mode split, appropriate density, and the extent of diversity of land-uses that maximizes self-contained trips.
The supply of parking, an intersection between mobility and land-use, entirely depends on minimum parking requirements that fail to account for complex relationships between parking supply and demand. Minimum parking requirements in cities is a likely cause of increased driving among residents and employees. To the contrary, data from Toronto centre suggests that more than half of underground parking remains empty whereas on-street parking is close to occupied during peak periods, indicating a shift of land-uses and a demography that prefers easily accessible parking spaces. Innovative mobility, particularly on-demand/shared systems, has big implications on a city’s parking requirements, having a car without needing to own or ever park one. Despite municipalities updating their parking requirement to reflect high-density uses, sustainable and shared mobility impact on parking demand is largely unknown. Utilizing a multimodal mobility planning model, the impact of different sustainable and technology uses on parking demand are estimated to reflect the need and create an opportunity for market-based pricing.