Dispatches from District 48
Thanks to a commenter, the short story from Omni that was so reminiscent of the China traffic jam was "The Great Moveway Jam." The blog Cedar Posts and Barbwire Fences found it online:
Part One is Here
Part Two is Here
"The Roads Must Roll" by Heinlein was probably better.
China does strike me as the kind of place that might contemplate a Moveway-like "solution" to this massive jam, eerie as that sounds.