HAVERHILL — Margie Valentine rides the bus a few times a week from her home downtown to the Westgate Plaza shopping mall and to visit a friend in the Julian Steele apartment complex.

Occasionally, she hops the bus from the Washington Square station to places like Merrimack Valley Hospital and The Loop in Methuen. The 63-year-old retired medical secretary neither wants nor can afford her own car, she said.

Valentine said there's a core group of people she sees on the bus most days, but the number of riders has dwindled in recent years.

"It's pretty common to be on with only a couple of other people," she said. "Sometimes it's half full. Other times it's just me."

Valentine's not the only one who has noticed the large Merrimack Valley Regional Transit Authority buses rumbling through the city with scarcely a passenger aboard.

City Councilor David Hall said he sees it all the time, and he's doesn't like it.

"The buses are too big, often empty, and run too often — every hour," he said. "They show up to stops with no people waiting to ride. These big buses pollute the city, and they cause traffic problems. Smaller buses would be better, and less routes might be cheaper."

Haverhill will pay $361,000 this year for the local bus service — an amount based on a formula that considers the number of buses and routes in Haverhill as well as the city's size and population, MVRTA Director Joseph Costanzo said.

At Hall's request, the City Council has asked Costanzo to attend a future council meeting to answer questions about the Haverhill bus service and whether it is possible to use smaller buses and reduce the number of routes. Councilors also want to know whether the city could reduce the cost of the bus service by contracting it.

But Costanzo said the real problem is there aren't enough buses running in Haverhill. He thinks the city should consider adding buses and routes to increase ridership.

"The buses don't run often enough," he said, noting that a bus only leaves Washington Square every hour during the week between 6 a.m. and 6 p.m. — one of seven routes within the city.

"People aren't going to wait an hour, so over time they find other transportation," Costanzo said. "If it was more often, we believe ridership would be a lot more. The demand is there in Haverhill. We just need to find a way to better serve people there."

In the fiscal year that ended three months ago, there were 202,143 riders of MVRTA buses in Haverhill, Costanzo said. The service includes the seven local runs and two regional runs between Haverhill, Lawrence and Methuen and Haverhill, Merrimac, Amesbury and Newburyport.

The MVRTA is planning a study early next year to determine if the authority should purchase smaller buses for Haverhill when it buys its next batch of 12 in 2011, Costanzo said. The study will also look at whether the Haverhill service should be constricted, expanded or modified to include different hours, route and stops, he said.

"The service is all local option, so Haverhill can have more or less," he said.

However, he said buses can't be added until the authority leaves its Washington Square hub, which has only four bus bays.

A new bus station is planned in about three years at the so-called Nofsker site on Essex Street, next to the commuter train station and about a third of a mile west of Washington Square, Costanzo said. The new station will include seven bus bays, he said.

Mayor James Fiorentini said he has also asked the MVRTA to consider changing its Haverhill service, especially if it could save the city money.

"It would pain me to reduce the bus service because it is relied upon by some of our poorest citizens," the mayor said. "But in these trying financial times, we need to look at saving money wherever we can."

The mayor said he has received many complaints about the empty buses, as well as requests from residents for the MVRTA to tweak its service rather than cut it back.

"Some handicapped people who ride the bus to work have complained they can't work second or third shifts because the buses don't run at night," Fiorentini said. "Maybe we can change the service to work better without cutting it back."

Costanzo said ridership is up in some other area communities, but remains flat here.

"In Lawrence, we're up 9.6 percent over last year," he said. "The buses are always full in Lawrence. Often people have to stand. But we share the buses between Lawrence, Haverhill and Methuen, so that's a problem with going to smaller buses in Haverhill. But we may be able to find a way to use a mix of large buses and small buses in Haverhill."

Standard-size MVRTA buses have 35 seats, while the smaller ones seat 25 people, Costanzo said. Any new buses are also likely to be powered by "clean diesel" engines or be diesel electric hybrids, he said.