A consultant will be hired this summer to analyze controversial traffic restrictions on Reno Road NW, Thomas Downs, director of the D.C Department of Transportation, has announced.

The study, expected to cost about $50,000, will enable Downs to make a final decision by December on what he last week called "the single most divisive and time-consuming issue" city transportation officials have faced in recent years.

Downs said the consultant is needed because DOT traffic planners, neighborhood civic groups and local Advisory Neighborhood Commissions are sharply divided over future restrictions for Reno Road.

Downs made the announcement Friday to representatives of 20 civic groups at a discussion of hearing examiner Robert Andretta's recent recommendations on the Reno Road corridor.

Downs said the recommendations are arbitrary and do not include "compromise" solutions he seeks or ones he believes can be defended in the courts, which he said may decide the Reno Road controversy.

Andretta, in a report released last week after two long public hearings on Reno Road last spring, recommended that restrictions imposed last fall become permanent, with one southbound lane and two northbound lanes at all times along the 34th Street-Reno Road-41st Street corridor.

He rejected a return to the much-criticized reversible, rush-hour lane on Reno Road as "prohibitively dangerous." He also opposed limiting northbound traffic to one lane, as proposed by many residents, because "two lanes north promote efficient exit from the city."

Andretta, whose recommendations are not binding on Downs, also urged that parking be banned along the route.

Downs questioned the parking ban, although he announced as an interim safety measure that DOT plans to prohibit parking in the southbound lane of 41st Street-Reno Road between Western Avenue and Porter Street.

The consultant will study the three basic options being considered for Reno Road:

* Making the route one lane in each direction, as it was until 1950. That would limit the speed and volume of commuter traffic along the hilly road through the residential area.

* Keeping the present one southbound and two northbound lanes, which limit morning but not evening rush-hour traffic.

* Reverting to a reversible middle lane, which allows maximum morning and evening rush-hour traffic along the corridor.

The consultant also will study left-turn restrictions for Connecticut, Wisconsin and Western avenues--urged by Andretta--that would discourage shortcuts onto Reno Road through side streets, where residents have complained of heavy commuter traffic.

Downs asked a representative each from four area ANCs (3C, 3E, 3F and 3G) and from two civic groups to work with DOT on the consultant's study. The groups are the Reno Road Traffic Coalition, which favors restricting commuter use of Reno Road, and D.C. Citizens for a Safe Transportation Policy, which wants a return to full use of the street as a commuter corridor.