The noun car crash is used figuratively to designate a chaotic or disastrous situation that holds a ghoulish fascination for observers.

—Cf. also the expression car-crash television, which designates television programmes that are gratuitously shocking or sensational, or of embarrassingly poor quality in terms of dialogue, acting, etc.

Apparently, it was in the expression a car crash in slow motion that the noun car crash was first used figuratively.

The expression like viewing a car crash in slow motion was part of an extended metaphor in the following from Does life still begin at 21?, published in the Liverpool Echo (Liverpool, Merseyside, England) of Tuesday 5^th August 1980:

Does the 21^st birthday mean anything any more now that adulthood comes at 18? Sarah Forbes *, daughter of film director Bryan Forbes and actress Nanette Newman, tells why she thinks reaching 21 is still important. […]
[…]
I left home at 17 armed with two pieces of advice from my father. He said: “Don’t go to bed with anyone for whom you have no affection whatsoever. You’ll wake up the next morning feeling vaguely dirty.
“And never go out with anyone devoid of a sense of humour, because no matter how physically attracted you are to that person it will never last because you need 90 per cent humour to survive.”
They never read me the riot act although rather like viewing a car crash in slow motion, they must have foreseen the inevitable accidents awaiting me—especially those involving a broken heart.
I suppose they knew that the moment they warned me to brake, I would, with the typical arrogance of youth, feel compelled to accelerate.

* Sarah Forbes was born on Thursday 21^st May 1959.

Ed Campbell used the expressions like car crash in slow motion and like watching a car wreck in slow motion in the following, published in The Baytown Sun (Baytown, Texas, USA) of Friday 12^th December 1986:

L.A. loss
Like car crash in slow motion

[…]
[…] Monday night, when the Seattle Seahawks administered a 37-0 fanny-kicking to the Raiders in front of a stunned national television audience […] I […] watched the relentless hammering until the bitter end. It was sort of like watching a car wreck in slow motion. There was a grisly fascination in watching this football team, which I’ve seen in person or on TV probably 100 or more times, crash and burn like never before.

The first two occurrences that I have found of the expression a car crash in slow motion used without preposition such as like are ascribed to George Forrester Colony, president of the advisory company Forrester Research, Inc., based in Cambridge, Massachusetts, USA—these two occurrences are:

1-: From Wang layoffs signal tough days ahead for high-tech workers, by David Callaway, published in the Boston Herald (Boston, Massachusetts, USA) of Monday 1^st July 1991:

Wang Laboratories’ stunning announcement last week that it plans to lay off up to 4,000 more workers drove home a painful message to the Bay State’s struggling high-technology sector:
The bloodletting is far from over.
[…]
“I think there will probably be a layoff announced every quarter for the next two years,” said George Colony, president of Forrester Research in Cambridge. “I like to call it a car crash in slow motion: a long, slow, downward spiral.”

2-: From Will IBM’s New Strategy Restore Its Reputation?, by Kiplinger’s Personal Finance Magazine, published in the Pharos-Tribune (Logansport, Indiana, USA) of Sunday 1^st December 1991:

One analyst who wouldn’t own the stock right now is George Colony, president of Forrester Research in Cambridge, Mass., which analyzes large computer makers’ strategies. Colony thinks that without radical change, Big Blue is in big trouble.
“IBM is essentially a car crash in slow motion,” he says. “It is going to lurch from disaster to disaster for years to come. Just for shareholder value, this company needs an overhaul.”