Landstar System Inc. believes it will continue capturing new business from shippers as many adopt the core carrier concept and pare the number of truckers they use.

"We believe that there are many different market niches. There is no single transportation universe," said Jeffrey C. Crowe, Landstar's chairman, president and chief executive.The Shelton, Conn., company is parent to nine motor carriers, the largest of which is Landstar Ranger, the Jacksonville, Fla., truckload carrier.

Landstar's plan is straightforward, Mr. Crowe told a meeting of the New York Chapter of the Transportation Research Forum here.

The company doesn't waste time focusing on business sectors it knows little about, such as retailing. Instead, Landstar concentrates on four industry segments it has experience in - automotive, steel, chemicals and refrigerated cargo.

And this year, the strategy has paid off. Other truckload carriers that count retailers among their core shippers are reporting weaker earnings due to the soft economy, said Burton M. Strauss Jr., a securities analyst with Lehman Brothers.

Landstar posted net income of $7.8 million, or 61 cents a share, on revenue of $308.1 million in the second quarter. In the same period a year earlier, the company reported net income of $6.6 million, or 51 cents a share, on revenue of $250.2 million.

Landstar has achieved much of its growth through acquisition of privately held truckload carriers. It also focuses on small to mid-sized companies in mid-sized cities such as St. Louis, New Orleans or Indianapolis.

He said surveys show that the top 25 accounts at most publicly traded motor carriers represent anywhere from 50 percent to 75 percent of their business. It is the reverse at Landstar, where the top 100 accounts make up only one- third of its business.

While many motor carriers have spent millions to install Ground Positioning Systems that use orbiting satellites to track the movement of trucks, Mr. Crowe said traffic managers don't really care whether a GPS can find a truck. ''What they care about is the ability to redirect that truck if what's on it needs to be rerouted," he said.

That's why Landstar spent $12 million to $15 million on management information and communications systems, enabling its mostly non-union, owner- operator drivers to remain in constant contact with dispatchers, which Landstar calls driver counselors.

Out of 10,500 Landstar drivers, over 9,500 are owner-operators, Mr. Crowe said. About 200 of these drivers for Landstar Ranger, are Teamsters. The owner-operators permit the $1 billion company to operate with just a $50 million capital requirement.

With such low overhead, Landstar plows 75 cents of every revenue dollar back to its owner-operators, Mr. Crowe said. The carrier's 900 local field locations absorb another 7 percent, leaving 18 percent of revenue for the corporation.

This year, despite increasing competition in the truckload sector, driver retention headaches and a lackluster economy, Landstar is on target to boost revenue by 20 percent and post a 5 percent margin, Mr. Crowe said.

In 1994, Landstar posted income of $24.7 million, or $1.90 a share, on revenue of $984.3 million, which made it the nation's third largest truckload carrier. The results were up from earnings of $11.7 million, or 99 cents a share, on revenue of $780.5 million in the previous year.

But keeping drivers remains a problem. Driver turnover edged up slightly

from 68 percent to 71 percent at Landstar's carriers. Still, this is far superior to the average 110 percent to 130 percent turnover rate at some truckload carriers, Mr. Crowe said.

Driver retention is such a problem in the industry, that J.B. Hunt Transport Services Inc., North America's second largest truckload carrier, spends $38 million a year to keep drivers, said Mahlon "Buddy" Moore, the carrier's Northeast regional marketing manager.