Pretty sure that's a toll booth. They widen to allow cars to queue and then narrow back down to transition back to free flowing traffic. It's not a 50 lane highway merging to 20 lanes, it's a 20 lane highway widening into a 50 lane queuing area and then merging back to 20 lanes to continue being a highway.

If it was just a hilarious engineering fail where someone genuinely decided to just terminate a 50 lane highway onto a 20 lane one, what's the structure for? To capture road rage moments for the latest RedNote compilation? Every time a highway does narrow, I've never seen a random structure overhanging the bottleneck.

Here's one in the glorious freedom country:

(Source)

Is this a 20 lane highway merging into a 3 lane bridge?

But yes, China does have a car dependency problem. Something the government has acknowledged and is implementing aggressive policies to combat. From building full metro systems in all major cities in the same time it takes NIMBYs in America to shoot down a single line, to high speed rail, to literally restricting who can drive on what days based on whether you have an odd or even first number on your license plate. What's America doing? Oh right, doubling down on car dependency and killing what little alternatives there were and calling people who speak out against it "woke."