Automobiles aren't the only type of electric vehicle (EVs) that are gaining traction as the transportation industry looks to reduce carbon emissions. Mass transit systems that have typically depended on diesel-powered buses are looking at different propulsion systems to reduce emissions that are a contributor to poor air quality as well as carbon dioxide in the atmosphere. Natural gas-powered buses have become quite popular, and with the vast supplies of US gas
now available thanks to fracking techniques
in extensive shale gas deposits, that trend will continue. But improvements in electric bus technology have made that a competitive alternative. Electric bus companies such as Proterra (Figure 1), which saw sales of its buses double from 2015 to 2016, believe that savings in fuel and maintenance costs, together with the environmental benefits, make them an ideal choice for addressing city, university, and commercial transit needs.
Public Bus Systems
Public buses, in particular, are perfect candidates for electrification given that a public bus can take 40 or more cars off the road; they drive limited and known routes which allows for a very focused infrastructure for in-route charging; and they are housed overnight in a large central building or location which means a long duration full-charge is not an issue. However, until recently electric bus service in the United States has been limited to small applications, mostly associated with airport transit. Travel range due to limited battery capability has been a major obstacle as it has with EVs. If a bus cannot travel its required distance on a single charge, time must be included in the route schedule for intermediate charging. This lengthens and/or disrupts bus rides, increases operating costs, and requires capital investment in charging stations along the bus routes.
One trendsetter has been Foothill Transit, a provider that covers the far northeastern suburbs of Los Angeles and that started operating its first electric bus in 2010. As of the end of 2016 Foothill Transit had 17 electric buses, all made by Proterra, and had accumulated over one million total service miles. These buses have a range of just under 200 miles, and the bus schedules include short recharging periods while in transit, with a 10 minute fast charge giving an additional 30-40 miles of range. In May 2016, Foothill Transit announced that its 300-bus fleet would convert to all electric by 2030.
Proterra's latest bus can, called the Catalyst E2 (Figure 1 and Video 1), stores up to 660 KWh of energy (10 times the energy of the standard Tesla Model S) and can travel between 194 and 350 miles on a charge thanks to its regenerative braking system that can almost fully recharge the bus's battery packs in route. Proterra believes this bus is capable of handling the workload of nearly every U.S. mass transit route on a single charge. The buses will cost $800,000 or more, each, which is about twice the price of a comparable diesel bus. However, savings in fuel and maintenance costs, together with the environmental benefits, make them an ideal choice for addressing city, university, and commercial transit needs.
Driverless Electric Shuttles
Another application of electric bus technology, driverless electric shuttles, was tested on the streets of downtown Las Vegas in January 2017. A 10-day pilot program using a vehicle developed by the French company Navya (Figure 2) that can carry up to 12 passengers was operated on a short stretch of the Fremont Street East entertainment district. The Navya uses GPS, electronic curb sensors and other technology, and doesn't require lane lines for guidance. It has a human attendant and computer monitor, but no steering wheel and no brake pedals. Passengers push a button at a marked stop to board it. The vehicles have a top speed of 25 mph and a range of about 90 miles for each electric charge and take about five to eight hours to recharge. The city believes such autonomous vehicles are cost efficient compared with a single bus and driver and has plans to deploy several later in the year.
Unique Electric Bus Concept
Perhaps the most unique and interesting "electric bus" concept today is the "Transit Elevated Bus" (TEB) built by a Chinese company, TEB Technology, that gets through traffic by driving over it (Video 2). Actually more of a train than a bus since it runs on rails, the vehicle is about 69 feet long, 26 feet wide, and 16 feet tall. The passenger compartment is elevated such that cars under 2 meters (6.5 ft) tall can drive freely underneath it. One carriage can carry as many as 400 people, and as many as four carriages can be linked like a train. Developers believe that one four-carriage train could replace 40 conventional buses and dramatically reduce fuel consumption and associated emissions. Although the test run in the city of Qinhuangdao in August 2016 was proclaimed as successful, by the end of the year funding for the project appeared to have dried up, and the prototype was sitting on its test track, rusting and impacting traffic, with some believing the entire project was a financial scam.