Self-driving mobility services are likely to be adopted quickly in high density urban areas. In these regions, car ownership is likely to fall significantly. Several studies have shown that one autonomous taxi might provide sufficient transport capacity to service the mobility needs which are currently fulfilled with 6 to 10 privately owned vehicles. These studies have considered local motorized mobility in large cities such as Ann Arbor, Lisbon, Austin and others.

But how will autonomous fleets impact mobility and car ownership in less densely populated areas? About 86% of the US population live in metropolitan statistical areas (i.e. areas that have a relatively high population density at its core). These are not limited to the great cities and agglomerations on the west and east coast but include much smaller areas such as the Grand Forks metropolitan area which comprises 2 adjacent counties in North Dakota and Minnesota with about 100,000 inhabitants (in 2014) and a population density of 11 people per km square. Of course, self-driving mobility services will be very viable in the urban core of this metro area where about 60,000 people live. The remaining 40,000 people living in rural parts of this area have significant, predictable mobility demands for trips towards and back from the urban core. Thus there is a potential for self-driving mobility services even in the outer, less densely populated parts of metropolitan statistical areas. A further 8.6% of the US population live in in micropolitan statistical areas (i.e. areas which are centered around an urban cluster with at least 10,000 but less than 50,000 people). The remaining 6% of the US population live neither in a metropolitan nor a micropolitan statistical area (see the white area in the map of metropolitan and micropolitan areas in US). It is instructive to consider their situation.

Let’s take Sidney, Montana as an example (Google maps): This is a small town with just about 5,000 inhabitants in eastern Montana. It is far away from more populated centers. The nearest larger city is Williston, ND with about 20,000 inhabitants at a distance of 70km. The next city with more than 100,000 inhabitants is Billings, MT at a distance of about 430km. There seems to be a significant mobility demand for trips to Billings: more than four flights leave for Billings every day (airfare about 40 USD). Uber is already active in this town and popular destinations/pick up spots include the airport, high school, health center and Holiday Inn Express.

The US currently has a stock of about 240 million light duty cars, which translates to about 750 cars for a thousand people. Because this ratio is higher in areas with lower population density, there should be significantly more than 5*750=3750 light duty cars in Sidney. Because a large share of the daily trips are local, and because their average speed is high compared to the speed in congested cities, autonomous fleets should be able to provide high-yield mobility services with a relatively small fleet. With a replacement rate of 1 to 7, about 535 self-driving vehicles could theoretically replace the town’s entire vehicle stock. The local mobility demands of 5000 people are also large enough that a mobility services provider can start with the smallest economically viable fleet size of probably somewhere between 10 and 20 cars and then grow the fleet as demand picks up. The low regional population density has an interesting consequence for non-local trips: The number of typical destinations is small; the number of routes people can travel from/to Sidney is quite limited. Therefore the potential for on-demand shuttles is high; Williston, with it’s Walmart (about a 1 hour drive) is an obvious target. Such shuttles have another side effect: they can provide the same mobility service to all locations which they pass on their route. Such shuttles therefore effectively will bring access to self-driving mobility services to some very rural dwellings.

Today, households in low density areas of the US have much higher car ownership rates than the rest of the population: there simply are  no viable alternatives. Self-driving cars fundamentally change this situation. Wherever there is a minimum of demand for personal mobility, self-driving mobility services become economically viable. The number of persons needed to sustain a self-driving taxi resource is rather small; towns with just a few thousand of inhabitants should always provide enough demand to allow a small fleet of self-driving taxis to operate. Initially it may only be the seniors who use these services but then households will start to think about the number of cars they really need and gradually demand for these services (and with it, supply) will increase.

In many lower density areas of the United States, car ownership is a prerequisite for finding work and – as a consequence – people without cars suffer and economic opportunities are lost. For seniors access to medical services and just getting around can be extremely difficult. The young face similar problems. These examples show that we can expect sufficient demand for self-driving mobility services in most parts of the United States – including many small towns and even in many areas that have low population densities. The impact of fleets of self-driving cars will not at all be limited to big cities!