Stop! Look! And Hasten!

Introduction: A famished Wile E. Coyote (Eatibus Anythingus) trudges across the desert floor, catching and eating anything that he finds to satisfy himself, ranging from a fly to an empty tin can, before being flattened by the Road Runner (Hot-roddicus Supersonicus). Wile E., after recovering, blinks his eyes and visualizes a wonderful Road Runner feast. Seeing no need for a comparatively tawdry can, he chases the Road Runner. Wile's low stance reduces his drag and allows him to approach the Road Runner until the bird rockets away. The coyote's eyes pop out of his sockets and he is left dejectedly planning his next scheme.
1. First, the coyote uses a pulley, rope and rock trap to smash the passing Road Runner, evidently hoping the extra complexity will stop himself from being squashed instead. No dice; Wile E. is squashed by the rock as the Road Runner stops and mocks him.
2. The clearly angry coyote, with a lasso in the road, listens for the Road Runner, but a truck trips the lasso first, dragging the coyote across the hard ground. Wile E. is left with a bare rear end from friction as he paces off the road.
3. The coyote builds a Burmese tiger trap according to a How-To book: dig a square pit in the road and fill it with a sheet camouflaged as road. He hides behind a rock and, hearing the Road Runner beep and the trap activate, dives in to capture his prey... only to instantly re-emerge and flee in terror, after which a real Burmese tiger (Surprisibus! Surprisibus!), stealthily climbs out of the trap and stalks off.
4. The camera displays a road with a pop-up grate intended to block the Road Runner; Wile tests its crank control successfully, but it fails to deploy against the speeding Road Runner. The coyote unsuccessfully tries numerous methods of unspringing the grate, then resumes the chase in outrage and is soon stopped by a railroad crossing. The Road Runner taunts his nemesis as he slowly prances the tracks, and the coyote is lifted into the air by the striped divider. After falling back down, Wile E. chases the Road Runner down the tracks, which run through mountains. The two pass by opposite lanes and the Road Runner signals the coyote, who stops cold after a few seconds and turns back, and after again running past the bird, he reverses only to find the Road Runner has escaped to a lower track. When he finally pursues the bird across the correct track, Wile is stopped by a train, and dashes in and out of a rockface; he sees the train proceed across an inferior track, and sighs with relief until a second train approaches from inside the rock. The apoplectic coyote holds up a circular STOP IN THE NAME OF HUMANITY sign, but since Wile E. isn't human, nothing happens except for the crash.
5. Next, Wile E. digs a corrugated culvert intending to mine the road with TNT, but the wires are short enough that he pulls the detonator over, which squeezes onto a loose rock and explodes the TNT while Wile inhabits the culvert.
6. The Coyote starts a speed motorcycle in pursuit of a passing Road Runner, but simply slams into a tree and is then jiggled around by the intense engine vibrations.
7. Now, Wile E. baits a white circle in the middle of a wide suspension bridge with bird seed, then hides underneath the bridge to cut out the circle as the Road Runner feasts. Instead, Wile falls along with the entirety of the bridge except for the bird and circle left floating in midair.
8. Finally, the Coyote attempts to outrun his rival by ingesting ACME Triple-Strength Fortified Leg Muscle Vitamins. He burns rubber on the road and dashes off, leaving the highway aflame. The Road Runner watches his foe approach and, from a standing start with a tongue-flapping beep, matches that speed instantly with about a one-second lead. This warp-speed chase continues, with the Coyote getting as close as a half-second at a valley and the Road Runner gaining distance on uphill grades, until they pass by the cranked-up grate, which finally rises for only Wile E. to smash into. The bird brakes and views his hapless rival before burning more rubber on the road, spelling out "That's all, folks" in smoke.
The End.

Question: Who hides underneath the bridge?
Answer: Wile E.