Cheaper theater tickets? It's not just a Broadway pipe dream.

An agreement to slash ticket prices and encourage production of new plays on Broadway bore fruit this past week when the first play produced under the cost-cutting experiment went into rehearsal.The play, "The Speed of Darkness," a drama about Vietnam veterans starring Len Cariou, Stephen Lang and Lisa Eichhorn, opens Feb. 28 at the Belasco Theater after two weeks of previews.

Top ticket prices will be $24 for all performances, with some tickets available for $12. Most Broadway plays have a top ticket of $40 or more. Last season's "Lettice and Lovage" charged $45 for prime seats and top tickets for the Tony-winning "Grapes of Wrath" had a $50 price tag.

The reduced ticket prices were made possible by the plan formulated last summer by theater owners, producers, craft guilds and stage unions, all of them taking royalty or salary cuts of at least 25 percent. Called the Broadway Alliance, it was the result of more than 18 months of negotiations by all parties. Musicals are not covered by the agreement.

"The object of the alliance is to cut the cost of production in half, cut the cost of operating in half and cut the cost of the ticket in half with the hope that it will generate a larger volume of production," said Robert Whitehead, one of the producers of "The Speed of Darkness."

The five-character drama, written by Steve Tesich, will be produced for about $400,000, less than half of the $800,000 to $1 million generally needed to bring a play to Broadway.

"Broadway needs the kind of serious, small plays where people really talk to each other," Whitehead said. "Naturally, these plays can't have 15 sets and 20 actors. They won't be the kind of productions where half the budget is going into scenery and special effects."

"The Speed of Darkness" concerns the reunion of two Vietnam vets in a small South Dakota town some 20 years after the end of the war. The play had its premiere in 1989 at the Goodman Theater in Chicago and was later reworked by Te-sich for productions in California and Florida.

Teisch, who won an Academy Award for writing the movie "Breaking Away," has not had a play on Broadway since "Division Street," a 21-performance flop in 1980.

"The only pressure I feel is that I'd like the Broadway Alliance to work, not only for myself but for other writers," the playwright said. "There are a lot of good writers out there. It would be nice for this thing for flourish."

The plan calls for profit-sharing by participants who take a salary cut or defer royalties until the play's original investment is recouped.

Each of Broadway's three major theater owners - the Shubert, Ne-derlander and Jujamcyn organizations - designated one of their least-used theaters for the productions.

The Belasco, which has had only two commercial tenants in the past six years, is a Shubert theater. Ju-jamcyn will use the Walter Kerr Theater, which recently housed "The Piano Lesson," and Nederlanders will use the Nederlander Theater.

Whether "The Speed of Darkness" succeeds or fails, another production of a new drama under the Alliance banner is planned for spring. "Our Country's Good" by English playwright Timberlake Wer-tenbaker is expected at the Neder-lander Theater in April. The play, set in 18th century Australia, comes to Broadway after a successful engagement last fall at the Hartford Stage in Connecticut.