SEC changing rules for when exchanges halt trading

(AP) WASHINGTON - Federal regulators are changing the rules for when a dramatic shift in value of the stock market or individual stocks triggers exchanges to halt trading.

The changes are aimed at curbing wild swings in prices such as occurred in the "flash crash" of May 6, 2010.

The Securities and Exchange Commission approved the changes, which were requested by the U.S. exchanges. The SEC said Friday they will take effect in a one-year pilot program to start by Feb. 4.

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One change affects circuit breakers, measures that automatically halt trading if the market falls by certain percentages. Circuit breakers will be triggered by smaller market declines than they are now, but the halts won't last as long.

In addition, rules for individual stocks will bar any trades outside specified price boundaries.