Daimler Truck, separated from Mercedes-Benz cars, starts trading shares.

Daimler’s car and truck divisions concluded an amicable divorce on Friday when shares in Daimler Truck began trading separately on the Frankfurt stock exchange.

The separation of Mercedes-Benz, the luxury carmaker, from Daimler Truck, which owns Freightliner in the United States, signaled the end of an era not only for Daimler but also the German economy.

The spinoff, announced in February, was the final chapter in a transition that began in the 1990s, when Daimler was a sprawling conglomerate that also made trains and passenger aircraft. Along with other industrial empires like Siemens, Daimler has been forced to jettison excess baggage to remain competitive.

For car and truck makers, the need to ditch unwieldy corporate structures has become even more urgent as they try to survive the shift to emission-free propulsion. One justification for the spinoff is that it will allow Daimler Truck’s managers to make decisions more quickly.

Daimler Truck is betting on hydrogen fuel cells for long-haul trucks, in contrast to competitors like Scania that favor batteries. It is not yet clear which technology will prevail.

A few decades ago, many German companies operated on the principle that bigger was better. That might have made sense when capital was harder to come by, said Martin Daum, the chief executive of Daimler Truck, because the more profitable parts of a conglomerate could generate cash for struggling units.

“We had globally very inefficient capital markets,” Mr. Daum said in an interview. “That supported the buildup of conglomerates.”

“Today, every business that has a compelling idea can raise money,” he said.

Whether Daimler Truck has compelling ideas will now be put to the test. The shares opened Friday at 28 euros (about $31.60) and rose as much as 8.5 percent, valuing the company at about $27 billion.

The new company is the largest truck maker in the United States by way of its Freightliner brand. Globally, Daimler Truck is also the largest maker of buses. Its other brands include Mercedes-Benz trucks and buses sold primarily in Europe and Fuso trucks sold in Asia.

Daimler Truck and Mercedes-Benz luxury cars will remain closely connected. Daimler, the parent company of Mercedes, will retain a 35 percent stake in Daimler Truck. The remaining shares will be distributed to Daimler shareholders.

BNP Paribas, Citigroup and Goldman Sachs are serving as listing agents for the spinoff.