It was a long truck - a landscaping trailer hitched to its back.

I would guess that sharp enough movements would not have done something constructive, so if the vehicle was already coming right around a curve, or going fast enough, they could have let off a little to go "straight" or continued to go "right", but going left would have done nothing reasonable.

In the article, though, the driver phrases it as them being too close, and turning just meaning hitting one or the other, so perhaps they came out into the street and he was just going too fast.