Since late January, stories about COVID-19 have centered around China, where quarantines and travel restrictions disrupted manufacturing and led to the cancellation of container ship crossings to the U.S. and Europe.

If shipping by sea to the U.S. or Europe takes an average of 30 days, the last shipments out of China after plants were closed prior to the Lunar New Year holiday on Jan. 25 will have reached their destinations.

So, we're about to get answers to questions that truckers have been asking for weeks: When will this novel form of coronavirus start to affect domestic freight? And how will we know what those effects will be?

Here are four things to watch that could change the demand for truckload transportation throughout the U.S.

1. Inventory levels

When the Federal Reserve issues its next Beige Book report on current economic conditions (scheduled for April 15), see whether inventories declined appreciably from the unusually high levels reported in January and throughout 2019. It will give you a big-picture view on inventory levels.

Then, within your own customer or transportation network, look for changes in the availability of certain items for which there are few sources elsewhere in the world (electronics and pharmaceuticals come to mind, as well as tires and truck parts).

There may be less demand for products here at home if consumers change their buying habits or stay home in order to avoid exposure, which will affect inventory levels.

At the same time, exports to Asia are building up in warehouses in North America, especially in the cold chain.

Is the makeup of the freight you haul starting to change?

This is a good opportunity to survey your customers and get a better understanding of how much they rely on imports.

U.S. businesses that maintain robust inventories are more likely to operate normally, even though imports are delayed.

The more dependent they are on imported goods from China, the more prepared you should be for supply chain disruptions and decreased freight demand, possibly followed by a spike when inventory flows into U.S. ports again.

2. Inbound container freight traffic

Keep an eye on loaded container volumes arriving at the Ports of Los Angeles and Long Beach in March. Combined, the ports handle nearly 38% of U.S. container imports, and they're focal points for trade with Asia.

The Port of Los Angeles announced Tuesday a 22.5% year-over-year drop in February loaded imports.

"As factory production in China remains at low levels, we expect soft volumes in March," Port of LA Executive Director Gene Seroka said in a statement. 

3. Truckload lane rates out of LA

As inbound load volumes drop on the West Coast, we're paying close attention to rates on lanes that originate in markets with large ports.

One lane to watch is the short haul from Los Angeles to Ontario, California, roughly 60 miles away. If there's subpar demand to move imported cargo from the port area to warehouses and distributions centers located further inland, we'll see it reflected in a 5% to 10% drop in spot truckload rates during the beginning of March.

4. Oil prices

The price of fuel aside, high crude oil prices are a boon to trucking companies because they spur demand for truckload capacity. More demand leads to higher rates.

Oil prices have fallen about 20% since late January to their lowest point since December 2018, near $50 a barrel, and forecasts are being lowered as the outbreak cuts into air travel and other activity.

American producers could start to shut down drilling locations here when the price of oil drops below the marginal cost of production, estimated at $35 to $40 per barrel.

This would reduce demand for domestic ground transportation, especially for flatbeds and rail intermodal equipment, leading to looser capacity and declining rates.

In terms of supply chains and economies worldwide, the impact of the coronavirus is still very much unknown. However, it does create an opportunity to reach out to your customers, assess how their transportation needs are affected and develop specific plans to help manage them.

Chances are, you'll bring a little certainty to a challenging time and strengthen your relationship as a result.