The D. C. Public Service Commission yesterday approved taxicab fare increases that average about 13 percent, giving cabdrivers their third fare increase of the year.

The increases, which go into effect at midnight tonight, push the cost of a one=zone cab ride from $1.30 to $1.45, with 70 cents for each additional zone crossed. The price of a crosstown ride traversing all eight city taxi zones rises from $5.50 to $6.35.

With yesterday's rise, cab fares have increased an average of 30 percent since the first of the year. The commission, which regulates the city's public utilities and taxi rates, said that the heftyincreases was warranted by the fact that the cost of operating a cab in the District has swollen by 32 percent since 1976, the last time before this year's increases that a fare increase had been approved.

The PSC'S decision received mixed reviews yesterday from cab drivers and their representatives.

"I'm satisfied . . . we're happy," said Norman Saunders, vice president of the Alliance of Taxicab Businessmen, the group that first filed for an unspecified rate increase last year.

"I think it is our efforts that really pushed this thing along," said Saunders, who praised Mayor Marion Barry for the support he had given to the cabdrivers' request for higher fares.

But on the street, cabdrivers expressed ambivalence.

"It's not enough," said Bob Lomax, 42, as he waited for a customer yesterday."I used to be able to fill my tank $13 to $14 at the most.This year it costs me $24. Everything has doubled (in price) for the maintenance on the cab."

"It's better than it was but it's not enough," said cabdriver James A. Rice, who was parked outside the Madison Hotel.

Commission member Ruth Hankins Nesbitt, who proposed the new fare levels, said, "I don't believe the rates as they exist today (prior to the decision) are just."

She said that she hoped the fare hikes would "encourage" drivers to improve service in outlying city areas, such as Anacostia, which cabdrivers have been reluctant to serve.

A 9.5 percent increase was granted by the three-member commission in January, the first taxi fare boost since Feb. 22, 1976. A 10-cent-a-ride surcharge was approved in June of this year to help defray rising gasoline cost.

The 30 percent over-all increase exceeds slightly the 27 percent fare hike that the taxicab industry, city government and the PSC staff had joined in proposing to the commission last month. Under that proposal, the average fare increase would have been about 12 percent.

Prior to that time, militant taxi drivers, faced with rapidly rising expenditures -- largely the result of gasoline costs -- conducted several demonstrations at the PSC. They also held partially successful cab strikes to demonstrate their concerns.

In yesterday's actions, the PSC also raised the afternoon rush hour surcharge from 60 to 65 cents, increased the charges for large suitcases and trunks from $1 to $1.25 per suitcase, and added a nickel to the charge for more than one large grocery bag, which will now cost a customer 15 cents to carry into a cab.

The price of a ride within a subzone of the downtown zone 1 was also increased from $1.10 to $1.20.

Since January, the cost of a one-zone ride has jumped from $1.10 to $1.45, or almost 32 percent, while the cost of an eight-zone ride has been boosted from $4.95 to $6.35, a 28.3 percent hike.

"I think this should please most drivers," said William J. Wright, president of the cab companies' Taxicab Industry Group which followed the Alliance to the PSC and requested a 10 percent increase.