Written with Jonathan Stewart.
The most important function of a city is to connect residents to jobs. Residents benefit from larger job markets that increase job choice and specialization. However, an individual’s personal labor market is smaller than the urban labor market because it is constrained by transportation. Residents will not consider positions that they cannot reach in a reasonable commute, typically about thirty minutes.
The World Bank has developed a tool for evaluating job accessibility in Buenos Aires. Job access can be measured from any point in the city using various modes of transportation and a commute time limit.
Below are two images created using the World Bank’s tool. The blue dot is a potential residential location in a suburb not too far from a metro line. Traveling by car one can access more than 5 million jobs in up to 60 minutes. Using transit only 770,000 jobs can be accessed. The job market from that location is 6.5 times larger for a resident who has a car than for one who only has access to public transportation.
However, this is only true for the marginal resident: if everybody was driving a traditional car and nobody was taking the metro, it would be impossible to access 5 million jobs by car. That is where the self-driving car may become an urban transport breakthrough: expanding the range of transit. For more on this discussion, see our earlier blog posts.