Q: In this task, you're given passages that contain mentions of names of people, places, or things. Some of these mentions refer to the same person, place, or thing. Your job is to write questions that evaluate one's understanding of such references. Good questions are expected to link pronouns (she, her, him, his, their, etc.) or other mentions to people, places, or things to which they may refer. Do not ask questions that can be answered correctly without understanding the paragraph or having multiple answers. Avoid questions that do not link phrases referring to the same entity. For each of your questions, the answer should be one or more phrases in the paragraph, and it should be unambiguous.
Passage: An inventory of medium and large mammals in the park confirmed the presence of 30 species in Saguaro National Park between 1999 and 2008. Of these, 21 were found in the Tucson Mountain District and 29 in the Rincon Mountain District. A partial list of the park's mammals includes cougars, coyotes, bobcats, white-tailed deer, mule deer, javelinas, gray foxes, black-tailed jackrabbits, desert cottontails, ring-tailed cats, white-nosed coatis, ground squirrels, and packrats. One endangered mammal, the lesser long-nosed bat, lives part of the year in the park and part of the year in Mexico.The wide range of habitats in the park supports a diverse population of birds including some, such as the vermilion flycatcher and the whiskered screech owl, uncommon elsewhere in the United States. Among the park's 107 bird species are great horned owls, cactus wrens, ravens, kestrels, turkey vultures, roadrunners, woodpeckers, hawks, quails, and hummingbirds, and one threatened species, the Mexican spotted owl.The park's 36 reptile species include desert tortoises, diamondback rattlesnakes (one of the more commonly seen snakes), coral snakes, Gila monsters, short-horned lizards, spiny lizards, and zebra-tailed lizards. Despite the aridity, three amphibian species inhabit the park: the canyon tree frog, the lowland leopard frog, and Couch's spadefoot, which lives in underground burrows, emerging to breed during summer rains. Forest fires, which create erosion-prone burned areas, have destroyed many of the leopard frog's breeding pools, which fill with sediment. The Arizona Game and Fish Department lists the lowland leopard frog as a species of special concern.Urban sprawl, air and water pollution, noise, light pollution, and a range of habitat restricted by human infrastructure put stress on the park's mammals and other animals, but the most serious immediate threat to them is roadkill. About 50,000 vertebrates a year die on the park's roads when they are hit by a vehicle. The Rincon Mountain District has few roads, but Picture Rocks Road, an east–west commuter highway crossing the Tucson Mountain District, is highly dangerous to wildlife. Attempts in 2002 to convert it to a hiking trail failed after the proposal met with stiff public resistance.
A:
What was attempted to be converted into a hiking trail?