Alexandria Police Officer Ronald W. Deitz has a simple way of gauging the changes in this historic community: He looks at the traffic and parking tickets he writes each day.

"The change became most prominent in the mid-1970s," says Dietz, 45. "Then we started getting more and more people coming to work in the city during the day, and more and more people coming in at night for the restaurants."

During the last decade, Alexandria's population has increased 7.5 percent from 110,000 to the current 119,000. Dozens of shops and restaurants have blossomed on lower King Street in the Old Town area, replacing several blocks of abandoned buildings and empty warehouses. On the fringes of Old Town, new office buildings have gone up.

The city government has not been idle in light of the development going on. In recent years, it has launched a program to attract busloads of tourists into the 230-year-old city.

And Deitz says his pad of traffic tickets has reflected most of those changes.

One result of the changes, says Dietz, is that "residents of the Old Town area gradually found themselves unable to park in front of their own homes, or even on the same block."

Because of residents' complaints, the City Council passed a residential parking permit program last year that prohibits nonresidents from parking on Old Town streets for more than three hours during the day.

"It's really had an impact," says Dietz. Last month, the traffic division issued 3,526 parking citations, a 25 percent increase over December 1978, the last month before the parking program went into effect.

Besides clearing residential streets, traffic fines have brought an estimated $600,000 in general revenues for the city, according to finance director Howard J. Holton. Ironically, income from the city's 675 parking meters totaled only $143,398 last year, officials said.

The man in charge of traffic enforcement is Deitz, who heads a force of six civilians and two sworn officers (including Deitz). The only job those eight people do is to make sure city traffic rules are enforced.

"Don't call us meter maids," says Deitz, a 23-year veteran of the city police force. "The people we have now do a great deal more than watch meters. pThey enforce the residential parking permit program, direct traffic at the scene of an accident or after a traffic light fails and put the (Denver) boot on any car they find with more than three outstanding tickets."

The heart of the traffic division is the six civilians. Each of them is paid $9,400 a year and given two weeks of classroom training before a week of on-the-street training.

"They wear a modified police uniform," Dietz says, "but they can't make arrests. The important thing about them is that they relieve the sworn officers of having to issue parking tickets, so they can concentrate on fighting crime."

The most frequently patrolled areas for possible parking violations include Old Town, the entire stretch of Mount Vernon Avenue from Braddock Road to the Arlington County line, and the industrial area near Eisenhower Avenue on the city's southern edge, says Dietz.

"We've been very pleased with the public response to the (parking permit) program," Deitz says. "People complain even when they know they're wrong. A lot of them claim one of our people waited deliberately for the meter to expire before writing a ticket . . . but the fact is we usually give a 15- or 20-minute grace period."

Police use a simple system to determine if a car is parked over the three-hour residential limit: a chalk mark is placed on one of the car's tires. Dietz says nonresidents try to thwart police by erasing the mark or moving the car forward so the mark won't show.

"It's technically illegal to move a car that's been marked or to erase the chalk," Deitz says. "They've got a 50 percent chance of fooling us once, but we start remembering the cars after a while."

Deitz says drivers also get frustrated when they have trouble finding a space on often crowded streets.

"People can get pretty angry when they can't find a parking space. They think they have a right to one, and so they disregard the signs.We've had a lot of shouting between police and civilians, but no violence," says Deitz.

In the Old Town area, 68 blocks are under the residential parking permit program, and 535 blocks in other areas of the city have some type of parking limitation.

"We're waiting to see what the effect of the Metro stations will be in the Rosemont and Del Ray neighborhoods," says Lt. Robert B. Dowling, who is Deitz's boss. "If commuters start leaving their cars in those neighborhoods and keep residents from parking there, we may suggest that the council consider a parking program in those areas."