Mobile Wi-Fi is ready to hit at least one daily passenger train in the United States, but there are still wrinkles to smooth out before its ready for rail commuters everywhere.

Silicon Valley commuters traveling by rail across the 1,000-foot-high Altamont Pass in California may think they are escaping snarled highway traffic, but they are also inaugurating Wi-Fi’s newest venue: railroads.

Mobility and the cheap wireless technology known as Wi-Fi would seem to go together like peanut butter and jelly, but until now, American Wi-Fi efforts have been pretty stationary. You could sit down, have a cup of coffee (or a burger and fries at some McDonald’s) and a side order of Wi-Fi. Check into a hotel, kick off your shoes, and log-on to the Internet. Cool your heels in and airline lounge and download e-mail while waiting for your next flight.

Most mobile Wi-Fi efforts have originated outside America. In Sweden, rail carriers are looking to Wi-Fi as another tool to snatch passengers from airlines. The Paris Metro experimented with Wi-Fi to boost riders. North of the border, Canada’s VIA railroad is continuing a trial co-sponsored by Bell Canada, Intel and Ottawa-based PointShot Wireless.

On September 3, PointShot begins its first U.S. trial of its RailPoint Wi-Fi product with California’s Altamont Commuter Express (ACE). The three-month experiment will offer ACE passengers free Wi-Fi access while making the three-hour,172-mile round trip from Stockton to San Jose, Calif..

“Onboard Internet access is the logical next step for a passenger-focused service like ACE,” said Chris Juelch, the rail carrier’s project manager for the PointShot trial.

An August survey of ACE passengers, mostly business commuters trying to avoid a single congested interstate freeway, found strong interest in using Wi-Fi onboard. Many said they would use the time to take online education courses. That’s not surprising since the survey was conducted in conjunction with the University of Phoenix, which heavily touts its online learning programs.

Although the service is free during the trial period, other details remain sketchy. The railroad service will get its Internet connection using satellite and cellular links, but as of late August, providers have not been found. PointShot “expects to have a provider by the start of the trial,” according to Shawn Griffin, president and CEO of PointShot.

Similar mystery surrounds the real-world data speeds rail passengers can expect for their mobile Wi-Fi experience. Griffin says PointShot won’t disclose actual data speeds “until after the trial is operational for some time,” in Canada. There, however, Bell Canada supplied the 400Kbps Internet downlink and CDMA cellular uplink.

Griffin says the three-month trial in the California will allow PointShot and ACE to answer how many users will take advantage of the service and what Wi-Fi services are popular with passengers. PointShot also sees the rail deployment as further proof of its mobile Wi-Fi products.

Julie Ask, a senior analyst with Jupiter Research, has some questions of her own. She would like to know if ACE is competing against airlines or cars and whether Wi-Fi is an added cost for passengers or part of their train ticket.

Despite her questions, she says Wi-Fi aboard commuter rail lines is a good value proposition for mobile employees.

“If you imagine that you can show up at a train one minute before it leaves, sit down and start working until the final destination, it is great productivity, compared to an airport,” says Ask.

Griffin says PointShot is in discussions with European and other North American commuter railroads about adding Wi-Fi.