NEC is developing a technology that allows users to flip back and forth between wireless LAN and mobile phone networks even when they are moving at race car speeds.

The technology could be useful for people who want high-speed Internet access for real-time voice or video transmission while they are speeding along on railways or highways, NEC said.

The company has tested a router that can connect a notebook PC to both WLAN access points and 3G base stations when the router and PC are in a car travelling at 200 kilometres per hour (124 miles per hour), according to Yukiko Yano, manager at NEC's Ubiquitous Platform Development Division.

WLAN offers megabits of bandwidth, but the access points are designed for clusters of people working in offices, homes and public places, and coverage is often patchy or non-existent outside urban areas. Mobile phone network coverage is much broader, but the communication speed is slower.

NEC's router, tested in May, is designed to let users take advantage of the speed of WLAN while automatically switching to 3G when WLAN is out of range. The router connects to WLAN access points at up to 6Mbit/s, and uses a WLAN connection whenever it can, the company said.

NEC developed an earlier version of the technology that can switch between WLAN networks - but not mobile networks - at even greater speed. It tested it by placing the router and PC in a Porsche that belted around a race track at 330kph.

The company said it thinks its new WLAN/3G router will also work at 330kph, but it couldn't find a car, driver and course to try it out right away.

NEC probably won't make products based on the technology for a few years, Yano said.