WiFi Rail announced they successfully carried about 15 Mbps of symmetrical traffic across a 2.6-mile test area of the Bay Area Rapid Transit (BART) system at up to 65 mph: The test covered above-ground and tunnel passages around Hayward, Calif. Roaming is seamless across the test area, the company said.

In an interview this morning, company founder and CEO Cooper Lee said that the secret sauce was in making "leaky coax" work, which is continuous copper coaxial cable that's left uninsulated in a particular fashion to allow signals to be passed over as if it were an antenna. Leaky coax is widely used for radio coverage in tunnels--it's even how AM/FM is carried through underground passages around cities.

WiFi Rail had to develop its own technology, including specialized amplifiers and high-performance filters coupled with Cisco radios and technology to pull tunnel service off. "It's a lot more than just tried it and it worked," said Lee. The system doesn't treat an entire run of coax as one access point, but rather they push signals from two access points, one on other end, using different channels. The signals taper off for a seamless handoff in the middle of the 2,200-ft run involved in the Hayward test.

Let me just point out that this is the sweetest possible network to build: Rights of way are controlled, the authority is apparently friendly, traffic is massive, commuters are already oriented to high-tech, cellular voice and data works only spottily, and the large scope of the service. If BART can have Wi-Fi, it's going to blow open the lid on commuter Wi-Fi across North America.

This initial proof-of-concept test, which involved working at times from 2 am to 4 am to access otherwise inaccessible equipment or avoid hours in which radio frequencies were in use, could lead to a system-wide deployment, pending BART's interest. The company would finance the deployment, which has a lot of characteristics that distinguish it from the spate of failed or faltering large-scale municipal Wi-Fi networks.

CFO Michael Cromar said, "We've built a business model that based on some relatively conservative assumptions, we think will give us pretty decent access to some private equity." He declined to disclose the expected cost of the network. The firm will benefit from existing coax in BART systems, and some backbone fiber, reducing their costs. Still, I would estimate such a system clearly will cost tens of millions to build--an exact price tag is tricky. BART comprises 104 miles, 43 stations, and 100m passenger trips (exit and entry) per year, or about 175,000 regular weekday riders.

The service, which tested out at 15 Mbps at 65 mph, would allow rich media--potentially from onboard equipment--along with VoIP and data. WiFi Rail might be in a position to extend cell carrier networks, too, using the same technology that's allowing them to overlay Wi-Fi on existing coax, or by providing bandwidth to carriers at strategic locations.

The network will cost users about $1 a day to use with a subscription, with various plans availble to reduce cost through usage or partnerships. The wholesale rate to roaming partners will be $1 for two hours: "It will be up to those services to decide what and how much they want to pass on to their customers the roaming fee," Cromar said.

An ad-supported option will also allow 5 minutes of use for every 30-second commercial viewed, through a partnership with JiWire. (Disclosure: I own a very small number of shares in JiWire, Inc.)

WiFi Rail won't start charging until its first phase is built, which they plan would span Oakland to Balboa Station in San Francisco, and take 3 to 5 months to build. The remaining system buildout time is roughly 15 to 18 months. Fees would be in proportion to the range of the system while it's under completion. Service is currently available in four downtown San Francisco locations at no charge; they've seen 6,400 registered users since they launched in June.

The folks at the company have ambition to bring their system beyond BART, even though just a single test segment has been completed. "We think there is a potentially very significant--you might call it a niche market, but it's a pretty significant niche market, for commuter inner-city rails, as well as metro systems, potentially even bus and ferry systems," Cromar said. "Anything that uses a predetermined path, where we could erect radios and antennas."

Part of the pitch to BART and other commuter systems will be video surveillance, which is a key aspect of interest to and funding by the Department of Homeland Security. Cromar said, "We've had six cameras all broadcasting at essentially 24 frames per second and higher, very high quality, and very high resolution, and still had much more than the typical Comcast cable modem or DSL conneciton that people would see in the home or office."

WiFi Rail has opted to bring fiber to each node with 100 Mbps of symmetrical bandwidth available at each location in order to provide the full capability of 802.11g. They're already thinking about 802.11n, trying to plan the network to be futureproofed with only radios needing swapping instead of basic infrastructure.

Unlike so many of the municipal projects, in which access to utility poles, the availability of electricity, and other facilities and infrastructure questions weren't known until later, BART controls its track and has detailed information about every part of the system. Also, BART is a single multi-governmental entity that can, in fact, make a decision about WiFi Rail without the same kind of political process that delayed or killed muni-Fi all over. (Not to pretend that BART isn't political; rather, the institution is designed to make institutional decisions that don't involve separate legislative/executive wrangling.)

This also ensures a knowable--not clean--radio frequency environment. BART has other radio uses, but they're in known places and can be characterized. CEO Lee noted, "If I pull up my laptop here in downtown San Francisco, I get 100 or more wireless networks that pop up out of the buildings. In a metro environment, there's no way to control the interference from everybody." By contrast, "Nobody else is going to put any antennas in the trackway, it's not possible," Lee said.

Ultimately, adding Internet access to commuter services has a lot to do with increasing ridership, allowing transportation authorities to improve their bottom line, remove cars from the road, and be part of larger efforts in changing cities and suburbs. "Increased ridership revenue for them for the most part goes right to the bottom line," Cowper said, as incremental passengers typically carry very little incremental costs--until ridership increases enough that the numbers justify adding more service.