YONGSAN GARRISON, South Korea — The United States and South Korea agreed to changes in how they operate in the wake of an incident last summer in which two South Korean girls were crushed to death by a U.S. military vehicle on Highway 56.

South Korea’s government agreed to widen roads used by U.S. forces for training, and to improve road signs. U.S. Forces Korea agreed to better notify civilian communities of troop movements. And the two sides agreed to cooperate better during initial investigations of incidents.

“That’s a direct result of the Highway 56 incident,” said Robert T. Mounts, U.S. secretary for status of forces agreements.

The changes affect how the U.S.-South Korean Status of Forces Agreement — the rules governing U.S. forces in South Korea — is carried out. The agreement came under heavy fire after a U.S. armored vehicle crushed two South Korean girls last June.

The incident — in which two U.S. soldiers were tried and acquitted during courts-martial — sparked violent protests across the country and demands to revise the agreement.

“The agreements announced today improve implementation of the SOFA and address public concerns about the handling of future incidents,” said Air Force Lt. Gen. Lance L. Smith, deputy commander of U.S. Forces Korea, in a news release.

U.S. and South Korean officials have had “intensive” weekly meetings since December as part of the Special Joint Task Force, said Mounts, also a special assistant for international relations.

The agreements also focused on environmental issues and speedy payments for victims. The pact with South Korea now has the strongest environmental rules of any U.S. status of forces agreement, Mounts said.

The two sides completed rules governing how land returned to South Korea will be environmentally surveyed. Under the Land Partnership Plan — signed in March 2002 — 23 of 41 major installations will close by 2011.

Last week, U.S. and Korean officials announced measures to make advance exgratia payments, intended to help victims with medical or funeral costs within four days.

The 1942 Foreign Claims Act allows for exgratia payment to be made in non-duty cases. Under the act, the United States is not required to make the payment; instead, it is regarded as a goodwill gesture toward other nations.

But a group formed to protest the girls’ deaths said on its Web site it’s not satisfied with the revisions.

The Pan-Korean Committee for Two Girls Killed by a U.S. Army Armored Vehicle wrote, “Even if there is some progress … it doesn’t include the core demand of SOFA revision.”

The group wrote it should have the power to stop training activities and complained the environmental changes don’t affect areas still influenced by the U.S. military.

“We can’t satisfy the demand of all extremist groups” and nongovernmental organizations, Mounts said. “But we have done our best to do those things that we can.”