The U.S. Forest Service is sure to stir up controversy today when it proposes a new policy that would make it more difficult to construct roads in the 155 national forests in the U.S. Most such roads are built for logging, and many of them are eroding and dumping sediment into waterways, endangering fish. Under the proposal, Forest Service officials, when deciding whether to build a new road, would have to give significant weight to possible ecological effects and determine whether the agency would have enough money to maintain the road. Federal officials say the plan de-emphasizes building new roads in favor of maintaining existing ones. The proposed rule, which could become final in September, would affect forests that already have roads in them; in separate policy, the Clinton administration has proposed banning road construction in up to 50 million acres of roadless forests.