Flaking asbestos insulation on locomotive steam pipes has shut down half of Griffith Park's Travel Town for about two weeks, said Al Goldfarb, Department of Parks and Recreation spokesman. Starting today, about a dozen workers from Northern Asbestos Abatement Co. either will remove the asbestos-insulated pipes from the trains or enclose them in a protective shell, Goldfarb said. The remainder of Travel Town will be open, including museum exhibits, the train ride and aircraft display, he said. Asbestos was a popular form of insulation when the older locomotives were built. The cost of the repairs will be determined by the number of pipes treated. The flaking problem was first discovered in 1985, and many pipes were enclosed to protect park patrons from the cancer-causing substance, Goldfarb said.