One Autobot hides beneath the bridge (while helicopters search for them), while Sam's "car" races along the side of the river bed. When the hiding robot drops the kids, Bumblebee catches them, but is then captured by the military.

The bridge is on the northeast side of downtown Los Angeles, just east of Union Station. The address would be approximately 875 E. Cesar Chavez Avenue. *

Part of that chase takes place on a freeway, as the robots "roller skate" down the freeway and rip a bus in two (resulting in a fiery explosion).

These freeway fight scenes were shot mainly in San Bernardino County, on an empty stretch of the Foothill (210) Freeway, which was still under construction when the movie was made. These scenes were shot at the east end of the freeway, in Rialto & Fontana, between Sierra Avenue (on the west) and Linden Avenue (on the east).

(That's about 50 miles east/northeast of downtown L.A.)

Instead, they jumped 60 miles away, to the interchange of the Harbor (110) Freeway & the Century (105) Freeway, in the Athens / Willowbrook area of south L.A.

(In the photo above, the camera is looking north, up the Harbor Freeway.)