Costs and Benefits of Electrifying and Automating U.S. Bus Fleets

Diesel-powered, human-driven buses dominate public transit options in most U.S. cities, but produce health, environmental, and cost concerns. Emerging technologies may improve fleet operations by cost-effectively reducing emissions. This report analyzes both battery-electric buses and self-driving buses from both, cost and qualitative perspectives. Using the Capital Metropolitan Transportation Authority’s bus fleet, in Austin, Texas, potential adoption schedules are developed here, based on practical constraints, to find the financial break-even points of adoption beginning immediately or at the availability of self-driving technology. With limited rail options and an existing reliance on diesel buses, the Capital Metro system is representative of most mid-size U.S. city contexts. From a life-cycle perspective, buses with electric powertrains are currently more expensive than their diesel equivalents, but falling costs indicate that they will deliver cost savings soon, for standard use patterns. Electric buses also tend to provide environmental and health benefits through reduced emissions, while fuel-price stability benefits of electricity over diesel is valuable to fleet managers. Rider comfort and public perception of bus services may also be improved, thanks to electric fleets’ lower air pollution and noise impacts. With battery packs falling at an average rate of 14% annually (or 8% for leading manufacturers) (Nykvist and Nilsson 2015), battery-electric buses will become life-cycle cost-competitive in or before year 2022, with the specific year depending on the actual rate of cost decline and the diesel bus purchase prices. Reflecting the value of lower emissions ($55,000 per bus per year) is likely to give them an immediate (year 2017) cost advantage.Self-driving buses should reduce or eliminate the need for human drivers, which currently comprise 45% of Capital Metro’s operating budget, and represent one of the biggest expenses in any transit-bus fleet (at over $3 million per 12-year bus life, which Eudy (2016) lists as the expected life of a transit bus). They may also provide environmental, (additional) cost, and service-quality benefits, thanks to smoother and safer driving practices (requiring less fuel and lower insurance costs, for example). This technology is estimated to offer immediate cost savings upon introduction. Recognizing bus lifespans and driver contracts, and assuming battery-electric bus adoption beginning in year-2017, cumulative break-even (neglecting extrinsic benefits, such as respiratory health) occurs somewhere between 2024 and 2035 (depending on the rate of battery cost decline and diesel-bus purchase prices). This changes to 2023 to 2026 if self-driving technology is available for simultaneous adoption on new electric bus purchases beginning in 2017. Transit operators should begin budget planning now, for such fleet improvements.

  • Supplemental Notes:
    • This paper was sponsored by TRB committee AP050 Standing Committee on Bus Transit Systems.
  • Authors:
    • Quarles, Neil
    • Kockelman, Kara
  • Conference:
  • Date: 2018


  • English

Media Info

  • Media Type: Digital/other
  • Features: Figures; References; Tables;
  • Pagination: 6p

Subject/Index Terms

Filing Info

  • Accession Number: 01657941
  • Record Type: Publication
  • Report/Paper Numbers: 18-00259
  • Files: TRIS, TRB, ATRI
  • Created Date: Jan 25 2018 9:34AM