ALL new cars, taxis, vans and buses with front middle seats should have lap belts, and passengers should be forced to wear them, the influential Transport Advisory Committee recommended yesterday. The law is expected to be changed this year, when the use of back-seat belts will also become compulsory. But there are no plans to force vehicles to fit lap belts for the middle of the rear seat, or rear seat child restraints. Committee chairman Professor Leung Chi-keung said where rear middle belts were already fitted, using them should be compulsory. He said the Transport Department should also encourage parents to make sure their children used child safety belts in rear seats. ''Before there were suggestions it was okay to hold a child in your lap. But we know that is not sufficient to protect them. In a crash a child can impact with a force of 250 kilograms. A child can be thrown out of the window quite easily.'' He said passengers in the middle front seat had a far higher chance of being injured than others in the front wearing a seat belt. Only new vehicles would have to fit the front belts, and there would be a grace period of one year before the new law came into force. But passengers in vehicles already fitted with the belts should be forced to wear them, he said. The requirement was common in other countries. A trial run of an emergency plan to control container trucks at Kwai Chung was a qualified success, police said yesterday. The 41/2-hour police exercise was designed to test how police would respond to major congestion, such as a rush by container truck drivers to meet Lunar New Year deadlines or the reopening of the container terminals after a typhoon. The aim was to separate traffic bound for terminals one to five from traffic heading for terminals six to eight. The first part had been done successfully, a spokesman said, but there was congestion on Container Port Road South outside Terminal Six. Police had created an emergency exit through Poland Street to divert traffic to West Kowloon to deal with the problem. The spokesman said congestion in streets near the terminals was no more than had been anticipated. More than 60 police officers were deployed around the Kwai Chung Container Terminal to direct traffic. The trial was the second such exercise. The first was criticised when police undertook it on a Sunday when traffic was lightest.