Making Way for More Bikes in National Parks The debate over who should use the roads and paths of the country's national parks is consistently fraught. In California's Sequoia National Park, unkind words are sometimes exchanged when pack animals with their wide panniers encounter hikers kitted out with the latest R.E.I. gear on the trails behind Mount Whitney. The code of etiquette and safety governing such encounters is sometimes ignored, And there have been continual efforts to ban horses, burros and llamas because of their impact on the trails. This year Congress intervened to permit stock packing on national parklands in the Sierra after a court ruled in a lawsuit filed by the High Sierra Hikers that the current system for permitting stock violated the Wilderness Act. Now bicycles are becoming part of the whose-trail-is-it debate. On Friday, the National Park Service published a final regulation in the Federal Register giving individual park superintendents the power to allow bicycles on existing or new roads and pathways. The service's stated aim is to promote a healthy way to explore park areas where motor vehicles are not allowed. As the rule in the Federal Register noted, bicyclists already use "trails, fire roads, abandoned railroad right-of-ways and canal towpaths." The Park Service said the new rule would expand bicycle access "while preserving the service's responsibility to prohibit bikes in wilderness and other areas where they would have significant impact on the environment or visitor safety." The practical impact of the rule is to streamline the process of opening roads and trails to bicycles and to localize the decision-making, which had previously been handled by national officials and posed significant administrative hurdles to those seeking a change. But Jeff Ruch, the director of Public Employees for Environmental Responsibility, argues that the new rule poses a threat to backcountry areas that might some day be eligible for wilderness protections but are not now in line for official wilderness designation. Bicycle use is a form of mechanized transport prohibited in areas protected under the Wilderness Act, so new backcountry bike trails might disqualify some wilderness-quality lands from attaining wilderness status, he said. The Association of National Park Rangers made the same point in a 2009 comment on the bicycle proposal. "All these potential N.P.S. wilderness acres are vulnerable under the proposed rule to have their character changed in such a way as might eliminate their consideration for inclusion into the National Wilderness Preservation System at some later date," it said. Examples include the majority of acreage in some iconic national parks such as Yellowstone National Park and Great Smoky Mountains National Park. Dave Barna, a spokesman for the National Park Service, said in an interview on Friday that no bicycles would be permitted "in any wilderness area, proposed wilderness area" or area formally identified as having wilderness characteristics. But the rangers group said that it did not trust all park superintendents to resist outside influence from pro-biking interests in communities where bike rentals are a thriving business. "The proposed regulation opens the door to park management decisions that could permanently impair or impact potential wilderness acreage to a single decision maker, and that is a framework that can allow for disaster," it wrote. Some have called for separating bikers and hikers on the trails, either by regulating the hours when each group can use them or segregating trails and allowing hikers on some and bikers on others. The park service responded that parks would consider "time-of-day or alternate-day authorization of uses, one-way riding requirements on loop trails, and requiring bicyclists to dismount and walk their bicycle through congested areas." Thrill-seeking will be discouraged, the Federal Register notice said. "Individual parks may, for example, consider ways to accommodate the safe use of bicycle trails for slow- to moderate-paced access, sightseeing and exercise," it said. Generally speaking, thrill-seeking at fast speeds would not be an appropriate activity in National Park System units. Some commenters were concerned that bikes have been unfairly discriminated against and that the rule does not remedy this. But Mr. Barna of the park service described the new policy as "a reasonable compromise."