T.I.M.A.C.

K8, 2019.01.23

Summary

Some napkin math analysis by a non-expert suggests that the number of accessible destinations in a given time is roughly proportional to:

area density × transit speed²

The comparatively high speed and availability of the personal automobile allow it to access a very broad area (potentially about 2 million people), in a relatively short time, even if the area isn't very dense by city standards. Slower transport technologies require denser construction.

Napkin Math

Assume a car travels an average of 60 kmph (~37 mph, not far from the actual American average of 38 mph^[1]), including starts and stops. An average American commute is now over 25 minutes^[2], but let's round it up to 30 minutes to get a sense of what's in range of the car. In 30 minutes, the car will travel 30 km. As a radius, this covers an area of about 2,826 km² (several times the size of NYC).