There is no fireā¦. yet! What are they doing? Southern Pacific ran a vegetation control spray train on its Cascade Subdivision to apply a herbicide to prevent growth of burdensome Bracken fern which dies after each season and becomes an extreme fire hazard from brake shoe or smokestack exhaust sparks, igniting entire forests. The work train was moving only about 10 or 12 mph but the tunnel portals had to be hit quickly while within reach of the nozzles. Near Field, Oregon, April 17, 1964.