Public transportation investments in large metropolitan areas reap a better return, with more passengers adopting public transport, than those in smaller cities, according to a study conducted by researchers from the University of Sydney.

The research analyzed data collected from 48 metropolitan areas in the U.S., including New York, Boston, Minneapolis, and Atlanta, which showed a positive correlation between ridership, residential density, and the convenience of using public transportation.

The research drew on data collected by the University of Minnesota, measuring the number of jobs over 48 metropolitan areas that were accessible by public transit. Efficiency was measured by assessing whether improvements to transit influenced residential density.

It also revealed it was more beneficial for transport operators to expand in big cities than launch into undeveloped areas, as larger cities yield a greater return on transit improvement than smaller towns.

Car use declines with higher transit accessibility: Using a scaling model, the researchers found that with increased residential density, coupled with better public transit accessibility, the density of car commuters levelled-off and began to decline.

Residential location and commute mode choice are affected by accessibility of transport to jobs: The researchers’ models were derived from a database that measured each minute of the morning peak period (between 7 a.m. to 9 a.m.) over 11 million areas in the U.S. They found that jobs within a 45-minute commute from home most affected transit rider density. The findings support that transit investment should focus on mature, well-developed regions, which would attract proportionally more ridership than smaller cities.

Transit rider density rises faster than population density with increasing transit accessibility: Efficiency was measured by “returns of scale,” assessing whether improved access to public transport influenced residential density.

The research found that residential density did increase with improvements to the transport network, but not at the same rate as the take up of public transport.

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