When they think of Cambridge taxis, many Harvard students and city residents--including members of the Cambridge License Commission--think of beaten-up, early 1980's sedans, with temperamental drivers who speak little English.

In Cambridge, many taxi drivers have fought city regulations requiring them to drive clean, new cabs and have asked the commission to be generous in annual inspections.

But in an industry where some drivers seem to care little about their customers' comfort, Brockton residents Rita and Danny Hughes have built a steady following of Harvard professors, students and local entrepreneurs by offering a clean, smoke-free car and on-call service.

"They probably like my service--I keep my cab clean, and I don't have a partition," Rita says. "I don't smoke, and I air out my cab and spray it with Lysol."

Rita says she and her husband began driving a taxi in 1978. Since then, the couple has developed a group of regular clients by working out of the same taxi stand at the Harvard Business School for 15 years.

"I have driven most of the Business School professors," she says. "Usually I take someone, and they come back."

Rita says developing a network of steady customers has several benefits--most notably guaranteed business and larger tips.

"They tip good," Rita says. "I mean, they're just like steady customers."

"Steady customers take the edge off," Danny says.

Although the Hughes subscribe to the Ambassador Brattle dispatching service, most of their business comes from calls to a cellular telephone they have placed in their 1985 Pontiac Parisienne, Rita says.

"The phone pays for itself," Danny says.

Rita says she even picks up lunch for some of her regular clients.

"Many times I'll pick [my customer] up a sandwich so that when he gets on the plane, he will eat it," Rita says.

The Hughes' commitment to basic business practices has attracted business from customers all over the country, they say.

"About once a year we have someone call where someone else had recommended us," Rita says. "It's nice because you know you're giving personal service."