National

A shift to connected and automated vehicles (CAVs) could reduce the energy consumed by the U.S. light-duty fleet by 60% — or it could triple it, according to National Renewable Energy Laboratory estimates. The range stems partly from differing expectations of the engineering performance of CAVs and their associated infrastructure, but much more so from their anticipated levels of use.

Why it matters: CAVs are seen by some to herald a lower-energy future, but they could actually have the opposite effect if their convenience spurs more driving. 

Over 80% of the variable costs of driving are the in the value of the driver’s time. CAV travelers will reclaim part of that value by web surfing, working or sleeping. This reduced price will likely increase travel. Ultra-long commutes will become reasonable when drivers can simply hit the road at 4 a.m. and return to sleep for the ride to work. And when CAVs operate while empty, the traveler’s time is eliminated, enabling such uses as sending the car home to avoid parking costs downtown.

Counteracting these travel-inducing effects demands policies to support shared deployment in the form of on-demand transit, which could mix public and private elements, rather than a CAV in every garage. Vehicle sharing favors close-in areas, with their lower demand for driving, because their trip density allows vehicles immediate return to service with other travelers. But even a self-driving Lyft or Uber system can swamp congested streets while leaving transportation gaps elsewhere. 

The big picture: A transit system that integrates trains, buses and on-demand CAVs is the best scenario for energy consumption. But such a system requires proactive planning, rather than a default to the car-oriented policies inherited from an earlier era. 

Jonathan Levine is a professor of urban and regional planning at the University of Michigan.

Self-driving cars may increase transportation’s energy footprint

Ultra-long commutes will seem reasonable if you can sleep on the way to work.

Self-driving electric vehicle, Navya Arma, developed by a French company Navya Technologies SAS, during the first test drive on a public road in Tokyo, Japan on December 22, 2017.

A self-driving electric vehicle on a test drive in Tokyo. Photo: David Mareuil/Anadolu Agency via Getty Images

Energy

Autonomous vehicles

Expert Voices

Transportation

A shift to connected and automated vehicles (CAVs) could reduce the energy consumed by the U.S. light-duty fleet by 60% — or it could triple it, according to National Renewable Energy Laboratory <a class="gtmContentClick" data-vars-link-text="estimates" data-vars-click-url="https://www.nrel.gov/docs/fy17osti/67216.pdf" data-vars-content-id="6cf4c751-e255-4648-a2b1-34bde8afe7de" data-vars-headline="Self-driving cars may increase transportation’s energy footprint" data-vars-event-category="story" data-vars-sub-category="story" data-vars-item="in_content_link" href="https://www.nrel.gov/docs/fy17osti/67216.pdf" target="_blank">estimates</a>. The range stems partly from differing expectations of the engineering performance of CAVs and their associated infrastructure, but much more so from their anticipated levels of use.Why it matters: CAVs are seen by some to herald a lower-energy future, but they could actually have the opposite effect if their convenience spurs more driving.

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Technology

Conventional bus and train transit excels at moving large volumes of passengers along busy corridors, but struggles to provide cost-effective service in outlying areas, where circuitous bus routes operate with few hourly boardings. At the same time, on-demand transportation — Lyft, Uber and any of their future self-driving iterations — converges onto those busy corridors and exacerbates congestion. This mix creates unserved “transit deserts" with high need for public transportation but little availability.

The big picture: A more efficient system would better tailor transit technologies to their environments — with buses and trains on heavily traveled routes and on-demand transportation in low-density areas — and integrate sparse areas with mainline service to overcome transit’s perennial "last-mile problem" at the beginning and end of trips.

Ideally, travelers should be offered transportation services that match their trips. A trip along a busy stretch and ending downtown would be taken in trains or buses operating in exclusive lanes. Travel between two points in the outer suburbs might rely entirely on on-demand transportation shared between unrelated parties, akin to Lyft Lines or Uber Pool. Trips that span the territories would connect service types, increasing the usefulness of mainline transit to people whose origins and destinations are not within walking distance of the bus or train.

Reality check: A system like this will not emerge by itself: Transit operators will fall back on familiar service models, and on-demand transportation will tend to duplicate, rather than complement, mainline transit.

What to watch: Avoiding those pitfalls requires both carrots and sticks. Disincentives might include congestion pricing and access restrictions, such as high-occupancy vehicle lanes. Incentives for serving underserved areas and linking them with mainline transit require public investment. For example, transit agencies might operate on-demand service themselves, contract for such services directly or make subsidies available when qualified trips are booked.

How on-demand transportation could make public transit more efficient

The two forms of transportation need to be better integrated.

A Cable Car passes a line of taxicabs as they wait for fares in front of the St. Francis Hotel on January 21, 2014 in San Francisco, California. 

A cable par passes a line of taxicabs in front of the St. Francis Hotel in San Francisco. Photo: Justin Sullivan via Getty Images

Future

Public transport

Conventional bus and train transit excels at moving large volumes of passengers along busy corridors, but struggles to provide cost-effective service in outlying areas, where circuitous bus routes operate with few hourly boardings. At the same time, on-demand transportation — Lyft, Uber and any of their future self-driving iterations — converges onto those busy corridors and exacerbates congestion. This mix creates unserved “transit deserts&quot; with high need for public transportation but little availability.The big picture: A more efficient system would better tailor transit technologies to their environments — with buses and trains on heavily traveled routes and on-demand transportation in low-density areas — and integrate sparse areas with mainline service to overcome transit’s perennial &quot;last-mile problem&quot; at the beginning and end of trips.

Jonathan Levine

Stories

How on-demand transportation could make public transit more efficient

Self-driving cars may increase transportation’s energy footprint