D.C. Superior Court Judge Robert H. Campbell is being investigated by the city's Judicial Tenure Commission for alleged judicial misconduct in his handling of masses of tickets in traffic court, The Washington Post has learned.

Sources familiar with the investigation said it is focusing on alleged favoritism to firms that amass thousands of dollars' worth of traffic tickets on their fleets of vehicles but then are fined substantially less or nothing at all by Judge Campbell.

The commission, which can remove, publicly reprimand or otherwise discipline an errant judge, reportedly has questioned Campbell in private about the allegations.

A separate examination of traffic court records by The Washington Post, shows that in 1977, Campbell imposed only a low fine or suspended sentences in cases involving hundreds of traffic violations issued to businesses.

Among the example found by The Post are:

A Maryland construction firm charged with $9,600 worth of overweight truck violations was fined only $2,400 by Campbell, who then suspended the imposition of the sentence, which meant the company did not have to pay any fine at all.

Coca-Cola, Inc. pleaded guilty to 206 parking violations, which carried fines from $5 to $25 and was given a suspended sentence by Campbell.

Michael J. Mussomeli, who has been conducted to a Virginia messenger service, posted $6,019 in collateral he owed for 252 traffic charges and then went before Judge Campbell, who ordered Mussomeli to forfeit only $1,260. The rest of the money was returned to Mussomeli. That case, others involving Mussomeli, and 30 to 40 other traffic court cases involving large numbers of violations have been reviewed by the commission.

Campbell also was questioned by the commission about Mussomeli, a retired metropolitan police officer who was at one time assigned to work in the Superior Court, sources said.

During an interview in his Superior Court chambers late Friday afternoon, Campbell said, "I don't have any recollection of specific cases.

"I wouldn't know him "Mussomeli) if I walked into him . . . and I might have acted on his case.

"I don't recall speaking to him unless he was one of a number of people who came to the court."

Henry A. Berliner Jr., chairman of the D.C. Commission on Judicial Disabilities and Tenure, confirmed that the commission is looking into traffic court cases, as well as small claims and landlord tenant cases. He refused to comment further on the commission's activities.

The commission has discussed its initial findings with law enforcement authorities, which is seen as rare and serious action by persons familiar with the panel's past investigations of alleged judicial misconduct here.

Several sources said Campbell's cases that have interested authorities involve cab companies, messenger services and construction firms - all of which have large fleets of vehicles operating here and could benefit substantially from favorable treatment in traffic court.

Several months ago the commission asked court officials for the records of about 30 to 40 traffic court cases, some dating from 1976 to 1977. Some of the cases involved Campbell and another judge, George D. Neilson. Both Campbell and Neilson have frequently sat as judges in traffic court.

Campbell, the former chief of the law enforcement division of corporation counsel's office, has long been the subject of criticism in connection with his handling of traffic matters. After being appointed to the Superior Court bench in 1972, Campbell has, by his own account, spent 22 months in traffic court since 1973 and handled close to 100,000 cases.

Campbell's critics have claimed that the judge is too willing to jail some individuals for minor traffic violations while being lenient with firms that pile up hundreds of tickets, a charge that Campbell vigorously denies.

It is not unusual for defendants who have accumulated large numbers of violations to receive lesser fines once they make an appearance in traffic court.However, the commission is investigating what may be a pattern of favoritism in cases involving businesses with repeated violations.

In the cases involving Mussomeli, many of the tickets were issued to vehicles owned by the All State Delivery and Messenger Service, located in Arlington.

According to court records, in March 1977 Mussomeli posted $6,019 in collateral to cover outstanding fines for 252 traffic charges, all of which were parking violations, some as much as two years old. The court jacket on the case indicates that Judge Campbell ordered Mussomeli to forfeit only $1,260 on the tickets with the remainder of the money - $4,759 being returned to Mussomeli.

The following April, the records show, Mussomeli was ordered by Judge Neilson to pay $5 on each of 28 parking tickets for a total fine of $140. According to the records, Mussomeli had posted $590 in collateral, which court sources said represents the total statutory fines for the tickets issued. The remaining $450 was returned to Mussomeli, according to the records.

In May Judge Neilson ordered Mussomeli, who had posted $780 in collateral for 33 parking tickets, to pay only $165, the records show. The rest of the $780 was returned to Mussomeli.

In November 1976 Campbell ordered Mussomeli to forfeit only $74 of $154 collateral posted on five traffic charges. In December 1976, in a case also handled by Campbell, Mussomeli pleaded guilty to 53 charges, Campbell fined him $800 but Mussomeli was required to pay only $200, with the remainder of the fine suspended.

According to The Post's survey of traffic court records, in a case handled by Campbell in May 1977, a local construction firm was charged with 96 violations - carrying a fine of $100 apiece - of city regulations for overweight trucks. Court records identify the firm as "E and C Construction," which police said is Excavation Construction Inc. in Bladensburg, Md. The firm has several multimillion dollar contracts for work on the Metro subway stations, a source said.

Campbell fined the company $25 (rather than $100) each of the 96 charges, for a total fine of $2,400. But he suspended the fine, which meant the company paid nothing for the violations, according to court records.

Tickets in the court jacket show that in some cases the trucks violated by as much as 22,000 pounds the weight limit on trucks the city has imposed to protect street surfaces.

Sgt. W. T. Thrower, of the D.C. Police Department's traffic division, said last week that overweight trucks not only damage the city streets but pose a safety hazard to drivers, who may not be able to control the overloaded vehicles. Thrower said trucking firms "save money" by overloading trucks because fewer trucks - and thus fewer drivers - can then be used to do a job.

In April 1977 a case involving a firm identified in the records as "E and C Construction" also came before Campbell, with 41 charges related to overweight trucks and two parking violations, court records show. The firm pleaded "no contest" to the charges, Campbell imposed a $25 fine on each charge and suspended execution of the sentence, according to the court records.

Records shows that in 1976 a firm identified as either "E and C Construction" or "Excavation Construction" had five cases before Judge Campbell involving about 293 tickets, 13 of which involved alleged violations of weight regulations. According to the records, conction with 52 of the tickets and collatecal posted was forfeited in sentences were suspended in connection with the remainder of the tickets.

In June 1977, also before Judge Campbell, a defendant identified in the court records as Coca-Cola Inc., pleaded guilty to 206 parking violations - tickets that carried fines from $5 to $25, according to court records of the case. Campbell suspended imposition of sentence in all the cases, the records show.