TOD Versus TAD: The Great Debate Resolved...(?)

This paper discusses the distinction between transit-oriented development (TOD) and so-called 'transit-adjacent development' (TAD)--a label sometimes applied to less-successful TOD efforts. It is suggested that transport performance is the key factor distinguishing between the two outcomes--and that despite complexities, clearer quantitative benchmarks are needed. Much of the literature and discussion on TOD centres around a perceived failing of many TOD project attempts to deliver a 'genuine transit-oriented outcome'. Often, this discussion has remained at a thematic level, or has rested on subjective qualitative appraisal, or critique of design or built-form outcomes. With a few exceptions, researchers and experts have generally been reluctant to provide a clear benchmark for TOD success or failure--perhaps because so many well-intentioned TOD efforts fall short of initial expectations. This paper puts forward a proposal that mode share should be the apex metric for determining TOD project success or failure. It is suggested that a majority (50%+) of travel movements need to be accommodated by the sustainable modes (walking, cycling, and public transit) for a location to assume the label of 'genuine TOD'. Equally, other locations that attempt TOD, but do not deliver a sustainable travel majority, might be placed in the 'TAD' category. Benchmark figures from international precincts and locales are used to sustain this argument--with reference to the broader planning, urban development, and design contexts in which these ideas sit.