New and generally higher subway and bus fares go into effect today and tomorrow on the Metro system.

Subway fares will be increase everywhere on the system by an average of just over 1 cent a mile. Bus fares in the District of Columbia will not be changed with one relatively minor exception. Rush-hour bus fares on suburban bus lines are going up.

Most of the changes will occur tomorrow morning as commuters go to work. One change in bus fares will take place today the cost of a ride between Virginia and District of Columbia on weekends -- and at other nonrush hours -- will rise from 75 cents to 80 cents.

The higher fares were adopted in May by the Metro board. They are expected to reduced the bus-rail system's deficit of $120 million during the next 12 months by at least $3.6 million.

With the changes, Metro's fare structure will continue to be the most complicated in the United States and possibly in the world.

Under the new system, a Prince George's country resident who transfers from bus to subway at New Carrollton has the biggest single fare increase. A round trip between Bowie and the downtown Metro Center station, for example, will rise from $2.50 to $2.95.

Most Maryland commuters will pay from 25 to 35 cents more for a round trip. Most Virginia commuters will pay from 15 to 25 cents more.

Here is a rundoown of the various changes:

SUBWAY FARES -- Minimum fare of 40 cents for up to three miles in rush hours will rise to 45 cents throughout the system, and each additional mile will cost 91/2 cents instead of 81/2 cents. This will raise the cost of a trip by 5 to 15 cents for many, but not all, riders. The fare in nonrush hours, a flat 50 cents throughout the system, will not be changed. Metro considers rush hours to be from 6 to 9:30 a.m. and from 3 to 6:30 p.m. weekdays.

BUS SUBWAY TRANSFERS -- Passengers who change from a bus to a train will continue to pay two full fares. Passengers still can transfer free from a train to a bus in D.C. 1but passengers who transfer from a train to a bus to Maryland and Virginia must now pay an extra 10 cents.

PARKING FEES -- All day rates on Metro lots at the Landover, Cheverly and Silver Spring subway stations will rise from 75 cents to $1; at New Carrollton, the rate will go from 50 to 75 cents. Rates at all other Metro lots will remain unchanged.

D.C. BUS FARES -- They stay the same, 50 cents in rush hours and 40 cents at all other times. The only exception is the fare on the £1 route, the Capitol Hill express from Chevy Chase via Connecticut Avenue, which will rise from 50 cents to 75 cents in rush hours.

MARYLAND BUS RARES -- Rush-hour fares within Maryland will go up from 50 cents to 55 cents. Rush-hour fares between Maryland and D.C. will go up 10 cents, from a minimum of 80 cents to 90 cents. Noonrush-hour fares will stay the same: 40 cents within Maryland, 60 cents for a trip into D.C.

VIRGINIA BUS FARES -- Minimum rush-hour fares within Virgina will go up from 50 cents to 55 cents, with no change in the present extra zone charges for longer trips. Rush-hour fares between Virginia and D.C. will go up 10 cents, from a minimum of 75 cents to 85 cents. Nonrush-hour fares within Virginia will remain at 50 cents.

ELDERLY AND HANDICAPPED -- The basic fare stays the same, half of the regular nonrush-hour fares rounded downward to the nearest nickel. A maximum rail fare of 50 cents and a maximum bus fare of 40 cents has been set.

FLASH PASSES -- These two-week passes for the first time will offer substantial discounts and not just convenience to regular users of both rail and bus services. They cost $10 or $16, and provide between $5 and $6.25 worth of rail travel pluse either unlimited or liberal bus riding privileges.

A number of bus service changes including the beginning of a lift-bus service for wheelchair users on 12 city and suburban routes will go into effect tommorrow. CAPTION: Chart 1, Metrobus Fares, The Washington Post; Chart 2, Selected Round Trip Rush Hour Bus -- Rail Fares to Metro Center