A highly regarded federal government economist was fatally injured yesterday afternoon while riding his bicycle in upper Montgomery County, according to county police and associates.

Eberhard "Ed" Irmler, 50, who lived in Northwest Washington, was riding on Barnesville Road in the Barnesville area when he was struck by an automobile about 12:45 p.m. after a chain-reaction collision, police said.

Irmler was riding west on Barnesville Road when the accident occurred at the intersection with Peach Tree Road. Police said he and his wife had apparently ridden their bicycles from the District. It was not immediately clear where they were going.

According to police, a preliminary investigation indicated that a minivan that was heading north on Peach Tree failed to stop at a stop sign and collided with a car that was going east on Barnesville. The car then struck Irmler, police said.

He was flown by helicopter to the Maryland Shock Trauma Center in Baltimore, where he died, police said.

Colleagues and co-workers lauded Irmler as a "real nice guy," good friend and avid athlete who was known for sharply improving regulators' ability to monitor changes in the value of thrift institutions' portfolios. Such changes, often resulting from swings in interest rates, have been called key causes of the savings-and-loan crisis of the 1980s.

Irmler worked for many years in the Office of Thrift Supervision, which was set up after the crisis to keep a close eye on thrift institutions.

He was "one of the two or three people most responsible for the fact that the OTS today has the most advanced model for measuring interest rate risk among banks," said David H. Malmquist, director of economic analysis at OTS.

Irmler "was responsible for a lot of the mathematical modeling and some of the programming as well," Malmquist said. "Without his influence, it might never have happened, or might never have been the product it is today." According to Malmquist, Irmler eventually left OTS for the Office of Federal Housing Enterprises Oversight.

Another colleague, Radu Filimon, described Irmler as a "very athletic" man who had been involved not only in bicycling, but also in running and in-line skating.

Irmler analyzed risks at work, but, according to his colleague, he did not believe in incurring them on the road. "He was not a risk-taker" while riding, Filimon said. "He would go by the rules."

Cyclists are inherently vulnerable on the roads, said Pierre Summerville, a board member of the Washington Area Bicyclist Association. "You have to be so careful," said Summerville, who serves on the association's committee for bicycle safety education.

He said he always tells his cyclists that when something untoward happens, "whether you are right or wrong, you lose."