The drunk driver is to blame for the traffic jam occured yesterday.
REMINDER: NOT A TEACHER
(1) You have already been given
excellent answers.
(2) I just wanted to point out that although your first sentence (the one without the
relative pronoun "that") is now considered
incorrect English, kindly remember that
in earlier English it was
not that uncommon, among some speakers.
(3) So if you read such sentences, don't be too shocked.
(4) Here are some examples from the great George O. Curme in his masterpiece
A Grammar of the English Language:
I haue [have] a neece [niece]
is a merchant's wife.
I bring him news
will raise his drooping spirits.
It's the like of that talk you'd hear from a man
would be losing his mind.
There's no investment in the world
would give you a return like that.
Any man
can't fight for his friends [had] better be dead.
(5) The good professor was writing about 80 years ago. At that time, he
says, such sentences were still popular among many speakers of Irish English and,
he adds, in the "mountain dialect of [the American state of] Kentucky."