As the New York bus and subway strike enters its seventh day, people are asking why there was a walkout this year and never before. Labor and economics experts at Harvard and M.I.T. generally agreed that the answer can be found in the new faces and the circumstances that surrounded the negotiations

In previous years negotiations between the New York City Transit Authority and the Transport Workers Union have been deadlocked to the final hour. But Mayor Wagner, working closely with his city mediator, Theodore W. Kheel, and the president of the TWU, Michael J. Quill, was able to find a last minute solution.

During the period leading up to the strike deadlines of the past, Quill was always able to increase the urgency of the negotiations by battering the negotiators with the threat of a walkout. This was his bargaining strength. He entered the recent negotiations with the same militancy. But no matter how militant and emotional Quill has appeared in public, the observers said that he has always been rational and skillful at the bargaining table. In this instance, however, he has appeared irrational and obstinate in asking such a high settlement, a $180 million package.

Some of the people contacted attribute this change in behavior to pressure from within the union for a settlement more generous than the one negotiated two years ago which met opposition when brought up for TWU ratification.

Another observer, though recognizing union pressure, believes that Quill was not motivated by a challenge to his leadership but by a desire to obtain one last generous settlement before he retires Another observer said that Quill was determined to retire in style and felt a strike was the way to accomplish this.

Mayor John V. Lindsay, unlike his predecessor, is inexperienced as both a mayor and as a labor negotiator, and does not have the benefit of the "understanding" that has existed between Quill and the Democratic mayors since the inauguration of William F. O'Dwyer in 1946.

According to one source, Lindsay wanted to call a halt to settlements on the basis of the "understandings." He felt that because of it many inequities, for example wage differentials, of the previous contracts were swept under the table. To avoid this he wanted to arrive at a settlement through open collective bargaining.

As already difficult situation was further complicated by a personality clash between Lindsay and Quill. There is more to the rift than Quill's name-calling and Lindsay's condesending words to Quill. One source believes that Quill was out to show Lindsay "who was boss," possibly because the new mayor was altering the traditional methods of negotiation between the city and the union.

Quill has also been portrayed as reenacting the Irish Rebellion, pitting his force against that of the "English" mayor.

By the time Lindsay became mayor it was unrealistic to expect that a settlement, considering so many factors previously disregarded, and satisfactory to all, could be hammered out before the strike deadline.

Even disregarding the other factors that clouded the negotiations, the city was still in a bad bargaining position. Because of the T.A.'s lack of money due to its present deficit and Lindsay's campaign promise to maintain the 15 cent fare, the Transit Authority didn't think they could obtain the resources necessary to support an increase that the Union would have accepted before the strike deadline.

These are the factors, a new mayor, a belligerent labor leader, and the lack of resources to support a satisfactory settlement which combined to make a settlement before the deadline a near impossibility