Tesla Inc is developing a long-haul, electric semi-truck that can drive itself and move in “platoons” that automatically follow a lead vehicle, and is getting closer to testing a prototype, according to an email discussion of potential road tests between the car company and the Nevada Department of Motor Vehicles (DMV), seen by Reuters.

Meanwhile, California officials are meeting with Tesla on Wednesday “to talk about Tesla’s efforts with autonomous trucks,” state DMV spokeswoman Jessica Gonzalez told Reuters.

The correspondence and meeting show that Tesla is putting self-driving technology into the electric truck it has said it plans to unveil in September, and is advancing toward real-life tests, potentially moving it forward in a highly competitive area of commercial transport also being pursued by Uber Technologies Inc and Alphabet Inc’s Waymo.

After announcing intentions a year ago to produce a heavy-duty electric truck, Musk tweeted in April that the semi-truck would be revealed in September, and repeated that commitment at the company’s annual shareholder meeting in June, but he has never mentioned any autonomous-driving capabilities.

Tesla has been a leader in developing self-driving technology for its luxury cars, including the lower-priced Model 3, which it is beginning to manufacture.

Several Silicon Valley companies developing autonomous driving technology are working on long-haul trucks. They see the industry as a prime early market for the technology, citing the relatively consistent speeds and little cross-traffic trucks face on interstate highways and the benefits of allowing drivers to rest while trucks travel.

Some companies also are working on technology for “platooning,” a driving formation where trucks follow one another closely. If trucks at the back of the formation were able to automatically follow a lead vehicle, that could cut the need for drivers.

Silicon Valley startup Peloton Technology, for example, is working with several truck makers including Volvo on its platooning system, which it sees as a precursor to autonomy.

Tesla’s high-flying shares, up almost 70 percent this year, closed down 0.5 percent at $363.53 on Nasdaq, but rose slightly after hours.

Prototype Tests

An email exchange in May and June between Tesla and Nevada DMV representatives included an agenda for a June 16 meeting, along with the Nevada Department of Transportation, to discuss testing of two prototype trucks in Nevada, according to the exchange seen by Reuters.

“To insure we are on the same page, our primary goal is the ability to operate our prototype test trucks in a continuous manner across the state line and within the States of Nevada and California in a platooning and/or Autonomous mode without having a person in the vehicle,” Tesla regulatory official Nasser Zamani wrote to Nevada DMV official April Sanborn. He made no reference to any dates for potential road tests.

No companies yet have tested self-driving trucks in Nevada without a person in the cab. On July 10, Zamani inquired further to the Nevada DMV about terms for a testing license, an email seen by Reuters shows.

California DMV spokeswoman Gonzalez said that Tesla had requested a meeting on Wednesday to introduce new staff and talk about Tesla’s efforts with autonomous trucks. She said that the DMV was not aware of the level of autonomy in the trucks.

Tesla declined to comment on the matter, referring Reuters to the previous statements by Musk, who has discussed the truck in tweets and at the annual shareholder meeting.

Nevada officials confirmed the meeting with Tesla had occurred and said that Tesla had not applied for a license so far. They declined to comment further.

Skeptics

Musk has said that potential customers are eager to get a Tesla electric long-haul truck, but he faces doubt that the company can deliver.

While established trucking companies and truck manufacturing startups have poured resources into electrifying local package delivery fleets, battery range limitations have largely kept the industry from making electric trucks that travel across swaths of the country.

Lithium ion battery researcher Venkat Viswanathan of Carnegie Mellon University said electric long-haul trucking is not economically feasible yet.

“Your cargo essentially becomes the battery,” Viswanathan said of the massive batteries that would be needed to make range competitive with diesel.

Diesel trucks used for cross-country hauls by United Parcel Service Inc can travel up to 500 miles (800 km) on a single tank, according to UPS’s director of maintenance and engineering, international operations, Scott Phillippi. By comparison, the company’s electric local package delivery trucks travel up to 80 miles on a full charge. (Reporting By Marc Vartabedian; Additional reporting by Alexandria Sage.)