Compact development without transit: life-cycle GHG emissions from four variations of residential density in Vancouver.

Numerous studies have shown that compact, mixed-use, transit-oriented developments contribute to reduced use of automobiles and in turn contribute to lower greenhouse gas emissions. When everyday destinations are within walking distance, people are more likely to walk or cycle, and if transit is within walking distance people are more likely to use it. Other studies have shown that compact development enables reductions in building energy consumption that contribute further to emissions savings. The reduced emissions are assumed to rely on the combination of compactness and transit connectedness. However, this combination requires an extensive transit network covering large areas both of residential and of employment destinations. Such networks often do not exist and are too costly to construct. When they do exist, the transit networks often do not reach those outlying neighbourhoods with the greatest potential for future growth and densification. This paper therefore asks what emissions savings compact development can achieve in the absence of high-frequency transit. In an examinination of the life-cycle emissions of four variations of density in three different neighbourhoods in Vancouver, none of which is well served by transit, we found a wide range of emissions profiles. A mixed-use new urbanist development produced 22% fewer emissions than an adjacent development of large single-family homes, both of which were in a transit-poor area on the far edge of a suburban city. A high-density neighbourhood adjacent to a suburban city centre, and one adjacent to a central city centre, produced 50% and 67% fewer emissions than the neighbourhood of large single-family homes. Findings suggest that, while compactness may be most effective when it is coupled with high frequency transit, decoupling the pair and building compactness before or without transit can still yield considerable household emissions reductions. [ABSTRACT FROM AUTHOR]