If you attended the 1964 New York World’s Fair, as I did as an impressionable five-year-old, you probably rode General Electric’s Carousel of Progress, where robotic automatons sang, It’s A Great Big Beautiful Tomorrow, which has my vote as the world’s worst earworm. This ride celebrated the ways that technological innovations — particularly motor vehicle travel — improved our lives, and predicted that we will continue to travel faster, farther and higher in the future.

The Carousel of Progress failed to anticipate the downsides of the automobile age: high costs, sclerotic traffic, crash and health risks, sprawl, and choking air pollution. So, as we consider incorporating transportation innovations into our communities, there are good reasons to be cautious. New technologies and services can provide benefits, but often impose large and unfair costs. It is important to use comprehensive analysis when planning for new mobilities.

Lessons from the Past

To plan for the future, it is helpful to understand the past. During the last 120 years, new transportation technologies increased our mobility by an order of magnitude, but increased many costs by similar amounts. During this period, planning favored private automobile travel over slower, more affordable and resource-efficient modes. Governments made huge investments in highways and required property owners to provide costly off-street parking. This created communities where driving is convenient but other modes are often inefficient, difficult, and dangerous to use. The figure below illustrates the resulting household costs.

Household Transportation Expenditures

If you are a typical North American adult you own a personal automobile that you drive more than ten thousand miles each year. To do so, you must devote about a fifth of your household budget, and therefore a fifth of your workday, to paying vehicle-related expenses. These cost burdens are an order of magnitude higher than in 1900, and significantly higher in the United States than in other affluent countries. When evaluated by effective speed, which considers the time people spend travelling plus the time they spend working to pay travel expenses, automobile travel is often slower than bicycling or public transit, particularly for lower-income workers, as illustrated below.

Effective Speeds: Minutes per Commuting by Various Modes

Automobile dependency is particularly harmful to people who cannot or prefer not to drive. Mass motorization, it turns out, made many people worse off overall, particularly those in physically, economically and socially disadvantaged groups.

How can we avoid such pitfalls in the future? This is an important and timely question. More transportation innovations are under development than at any time in the past. These include micromodes (e-bikes and e-scooters), ridehailing, electric and autonomous cars, public transit innovations, telework, tunnel roads, pneumatic tube transport, air taxis (flying cars), delivery drones, commercial supersonic jets, and new logistical management strategies. Policy makers must make countless decisions concerning new transportation technologies and services. How can we ensure that these decisions are efficient and fair?

A Little Skepticism, Please

When planning for new mobilities, it is important to be a little skeptical. Advocates often exaggerate the benefits and overlook significant costs. Here’s an example. Optimists predict that autonomous cars will reduce traffic congestion, crash risk, energy consumption and pollution emissions, but to achieve these benefits they require dedicated lanes for platooning (many vehicles driving close together at relatively high speeds). When should communities dedicate special lanes for the exclusive use of autonomous vehicles? How much should users pay for the privilege? How should this be enforced? Who will be liable if a high-speed platoon crashes, resulting in a multi-vehicle pile-up?

Similarly, delivery drones may provide large benefits when delivering critical medicine or equipment to isolated areas, but you might object if drones frequently delivered pizza and beer to your neighbor’s late-night parties. Who decides whether the benefits (quicker delivery of food and drink) are worth the additional noise, risk and disruption?

Some new mobilities tend to increase vehicle travel and traffic problems. For example, if parking is priced but road use is free, autonomous vehicle owners will rationally program their cars to drive around the block, sometimes for hours, or drive home, in order to avoid paying for parking. Ride hailing and taxies generate lots of “deadhead” mileage — empty vehicle travel to pick-up and drop-off passengers. As a result, with current policies, autonomous vehicles are likely to increase traffic congestion, crash risk and pollution emissions. Only more efficient road pricing can prevent those problems. Are policy makers ready?

It is also important to consider the new mobilities’ user experience. Artistic renderings show happy passengers in clean and comfortable autonomous cars, air taxis, and pneumatic tube transport, but the reality may be less appealing. Autonomous taxies will sometimes contain trash, suspicious stains or unpleasant odors left by previous occupants; air taxis will be cramped and noisy; pneumatic tube transport requires passengers to be locked into small, windowless capsules that accelerate and decelerate at speeds that will make some people nauseous.

When Should We Fire the Chauffeur?

How soon will we all have autonomous cars? What will they cost? Who will benefit? Level 5 autonomous vehicles, which can operate without drivers under all normal conditions, are still under development. They may be commercially available within a decade, but if they follow the pattern of previous vehicle technologies, early versions will be expensive and imperfect. Vehicle purchasers will need to decide whether to pay thousands of extra dollars for a vehicle that will sometimes stop to await human instructions, and when a destination is selected will occasionally respond, “Sorry, I can’t go there” due to snow or heavy rain, or because it is not on the vehicle’s map.

Some benefits, such as reduced driver stress and more independent mobility for affluent non-drivers, can occur when autonomous vehicles are expensive and rare, but many predicted benefits will only be significant when they are affordable and common. The figure below illustrates my prediction of when this will occur. This analysis suggests that it will be at least 2045 before half of new vehicles are autonomous, and 2060 before most of the vehicle fleet is autonomous.

Autonomous Vehicle Sales, Fleet and Travel Projections

Glamorous versus Practical Modes

In practice, the most glamorous new mobilities often provide only modest benefits. For example, air taxis may be able to fly over roadway congestion, but most users will need to drive to and from terminals and wait for an available departure, so their door-to-door time savings will generally be modest. Similarly, supersonic jets may cut in-air travel times by half, for example, reducing London-to-New York flight times from eight to four hours, but considering travel to and from airports, loading and clearing customs, they will typically reduce door-to-door travel times by just 20-30%, and due to their high ticket prices will only be cost-effective for travelers whose time is worth thousands of dollars per hour. Once the novelty wears off, many travelers will probably choose more affordable and comfortable alternatives.

Some of these modes are expensive, so policies that support them tend to be regressive. For example, electric vehicle subsidies and autonomous vehicle traffic lanes primarily benefit the wealthy motorists who can afford costly new cars. How can communities ensure that lower-income residents receive their fair share of public investments?

The figure below rates twelve new mobilities according to the degree that they support or contradict eight objectives, including various user and community benefits, using a seven-point scale from +3 (best) to -3 (worst).

Of course, these ratings are somewhat subjective. Other people might have somewhat different priorities and judgements, but I think that the basic conclusions are robust: affordable and resource-efficient modes, such as active and micromodes, public transit, and Mobility as a Service, provide a greater range of benefits than expensive and resource-intensive modes, such as tunnel roads, pneumatic tube transport and aviation innovations. To increase efficiency and fairness, public policies should favor higher-ranking over lower-ranking modes.

The higher-ranking modes tend to be slower than the lower-ranking modes. In the past, transportation planning tended to favor faster but more-expensive modes over slower but affordable and resource-efficient modes. We now recognize the importance of balancing speed against other community goals.

For most households, the best new mobilities are the less glamorous but more practical modes: walking, bicycling, micromodes, public transit, bike- and carsharing, ridehailing, Mobility as a Service, and telework; these are the innovations that can improve our lives and communities the most. They provide true freedom and livability, not by increasing travel speeds or automating travel, but by reducing costs, providing more independent mobility for non-drivers, and reducing external costs including traffic congestion, risk, noise and air pollution. Electric and autonomous cars, air taxis, tunnel roads, pneumatic tube transport and delivery drones may be appropriate for some trips, but policy makers must prevent overuse.

This analysis provides some interesting and sometimes surprising insights:

• A transportation system must be diverse to serve diverse demands, including the mobility needs of people who cannot drive or have limited budgets. No single mode can satisfy everybody’s needs.
• Vehicle innovations tend to be implemented more slowly than other technological change due to high costs, strict safety requirements, and slow fleet turnover. Automobiles typically cost fifty times as much and last ten times as long as personal computers and mobile phones.
• Most vehicle innovations are initially costly and imperfect. It usually takes decades for new vehicle technologies to become reliable, affordable and common.
• Predictions that autonomous electric taxis will soon be cheap and ubiquitous, displace most private vehicle travel, and solve most transportation problems, are unrealistic.
• There is considerable uncertainty concerning new mobilities’ benefits, costs and equity impacts. Some new mobilities support, and others contradict, social equity goals.
• Communities must plan, regulate and price new mobilities to prevent problems and maximize benefits.
• The most glamorous modes are not necessarily the most useful, beneficial or fun. Affordable, resource-efficient modes tend to provide the greatest total benefits. To be efficient and fair, public policies should favor them over more expensive, resource-intensive modes.