General Motors Corp.'s assembly plants will undergo 42 product launches during 2002-'04 — nearly half coming in 2003 — according to charts in the auto maker's technical center.

Without providing vehicle details, the charts indicate 19 product launches in 2003 — five in every quarter except October-December, when production of four vehicles will begin. Of the 19 launches, 13 are new products, the rest are mid-cycle enhancements.

GM will be almost as busy in 2002 when it will launch eight new products: two by March, six in the second quarter, five in the third quarter and three in the last three months.

In 2004, launches are scheduled for every quarter except July-September when production is expected to begin on four vehicles. Five of the seven launches in 2004 will be new models.

A few years ago, GM would not have been able to handle them all without months of plant downtime. But the auto maker claims it is well prepared to pull off quick changeovers. “We now have a launch complexity index,” explains Gerald Elson, general manager of GM's Vehicle Operations. “We know exactly how complex a launch is going to be. We looked back at every project and said, ‘This is the launch complexity index for this.’ And that's why we're able to launch now in a very high quality and efficient manner.”

The index prevents GM from becoming too ambitious. “Don't launch a new powertrain, a new architecture, a new paint shop and a new workforce all at once,” Mr. Elson says.

GM's strategy to move its manufacturing focus through stages of transition is cutting plant conversion time. From 1986 to 1990, GM launched 13 products with an average changeover time of 135 days. With twice as many launches, that figure fell to about 105 days during 1991-'94. GM hit a 2-month average from 1995-'98 when it completed 20 launches. Since 1999, the auto maker reports 22 launches and says conversions now average weeks or days instead of months.