CHECKS on walkers on the MacLehose Trail will be stepped up this year to avoid losing tired entrants who fail to register their withdrawal from the event. The Queen's Gurkha Signals, who co-ordinate the 100-kilometre slog, spent hours searching for people they thought had gone missing in the rugged terrain last year. To prevent a repeat of the wasted effort, walkers will be checked twice at each of the nine checkpoints. They will be asked to present their bar-coded wrist bands at check-in and check-out stations, equipped with more efficient, supermarket-style laser scanners than those employed previously. Computers will record the walker's number and the time of arrival or departure in about two seconds. Trailwalker co-ordinator Major Sean Dexter said the new system was much safer because it showed whether a walker was lost or had just gone home. ''We know about those who are injured, it's the people who wander off at the checkpoints that we have to keep track of,'' he said. ''The new system is very fast for the runner. He just turns up, gets the confirmatory beep and goes on.'' Bar codes have been made shorter and wider to make them easy for the scanner to read, and the $920,000 equipment has been tested under rainy, muddy and sweaty conditions. Walkers can be located instantly at any stage of the walk, and this information will be shown on a large screen at the finish line. Support teams and medical units will also be kept up to date on the walkers. The walk will start on October 29, and the stations will stay open for 48 hours. Route clearance teams will follow behind the slowest walkers to make sure no one is lost along the way. The event has raised more than $20 million since 1981 for local charities, including Oxfam Hong Kong and the Gurkha Welfare Trust.