Large U.S. trucking companies are ratcheting back expansion plans after declining freight volumes cut into fourth-quarter profits.

The lower earnings reported by half a dozen carriers this week confirmed that companies were weighed down late last year by uneven retail sales, high inventory levels and a manufacturing slowdown. Based on their 2016 guidance, they expect more of the same over the next few months.

Trucking companies say they’re preparing for a prolonged downturn by reducing investments in their fleets. Their goal is to avoid creating a glut of trucking capacity, which would give shippers more power to negotiate lower prices for moving their goods, further squeezing carriers’ profits.

That is a dramatic shift from even a few months ago, when many carriers were set on bulking up, and swapping out older vehicles for new, more fuel-efficient models. But with freight volumes and pricing falling, trucking companies need to conserve cash.

“The large carriers…one thing we see in common is that fleet additions in that group have ended, and the outlook is basically to be flat,” said David Jackson, chief executive at Knight Transportation Inc., in a conference call with analysts after releasing earnings Wednesday. “Even the best operators have gone backwards a little bit. And I would add us to that group.”