Microsoft on Thursday plans to introduce a Web-based service for driving directions that incorporates complex software models to help users avoid traffic jams. The new service’s software technology, called Clearflow, was developed over the last five years by a group of artificial-intelligence researchers at the company’s Microsoft Research laboratories. It is an ambitious attempt to apply machine-learning techniques to the problem of traffic congestion. The system is intended to reflect the complex traffic interactions that occur as traffic backs up on freeways and spills over onto city streets. The Clearflow system will be freely available as part of the company’s Live.com site (maps.live.com) for 72 cities in the United States. Microsoft says it will give drivers alternative route information that is more accurate and attuned to current traffic patterns on both freeways and side streets.