Jim Todd, president of Hazel/Peterson Cos., rode on a bus tour last week peering through tinted windows and watching an emerald-green Prince William County countryside quickly change to the red dirt of construction and then to the pavements of residential and commercial projects.

Todd was one of 145 Northern Virginia developers, real estate sales people and builders whom the Prince William Chamber of Commerce brought together in the hope that they will play a role in the county's future.

We felt we had a lot to show the outside business community," said Mike T. Hall, chairman of the tour committee for the 800-member chamber. "We are opening eyes of developers."

Todd's firm plans a multimillion-dollar residential, commercial and office complex known as William Center on 542 acres in the northwest section of the county. "After riding through the county, I am even more excited about William Center," Todd said.

Prince William, according to Todd, "is the next logical step" in the business surge of the Washington area. Arlington and Fairfax counties do not have much space to accommodate more development, he said.

Linda S. St. John, executive vice president of the chamber, said the "timing" was right for a tour because many projects are under way. The chamber made it a point to invite entrepreneurs from outside the county; two-thirds of the tour participants were from other localities.

Reaction from several was positive. "The progress the county is making -- it's really mind-boggling that they have all those types of things going on," said Margaret Booth, a broker with the Springfield real estate and development firm R.L. Travers and Associates.

Mark G. Delany, a retail development specialist with First Capital Realty in Washington, said the tour gave him a helpful overview of the county. Delany and George R. Phelps, who works for the same firm, said Prince William, which has experienced a sizable increase in population, appears ready for the next phase of development: businesses to service the new residents and workers.

And, as more businesses break ground, a "domino effect" will follow, predicted Booth, who said that within five years the amount of new development will be considerable.

In 1983, the county had 400,000 square feet of new construction. In 1986, there was 1.8 million square feet of new construction; 2.3 million square feet is under way this year.

Thomson Hirst, president of a Reston firm that develops office parks, sent a representative to study the county because the business climate around Washington is changing rapidly. In a telephone interview, Hirst said he was not overly optimistic because land prices were higher than he expected.

Roger Snyder, county planning director, began the day's information blitz with a portrait of a county where the population has grown by more than 50,000 since 1980 to nearly 200,000 today, where the civilian labor force has increased by 30,000 during the same period and where commercial development has leaped from 10.8 million square feet to more than 17 million this decade.

"But, there is a price for growth," Snyder said.

The county desperately needs more commercial and industrial growth to help offset the demand for services created by the swelling population, planners have said. Industry and commerce account for about 14 percent of the county's revenue from real estate taxes, with the rest coming primarily from the residential sector. Ideally, the industry and commerce tax revenue level should be about 20 percent, county officials say.

According to Snyder, money is not the only consideration. He explained that the county can make for some interesting politics. "Our public has asked for more and better services but has repeatedly rejected bond financing . . . ," said Snyder, looking at the people who could aid in balancing the county's tax base.

During the tour, Snyder often mentioned residents' concerns, noting that developers have to be conscious of the role of the resident in the zoning process. Snyder suggested several times that the developers who worked closely with citizens groups were able to make peace with them if projects were adapted to address potential problems.

In a telephone interview, Anne Snyder, a citizen activist who has opposed a number of developments in the county, said there was nothing wrong with the concept of an economic development tour, but she wished that the chamber would have included citizen representatives.

She said she is sympathetic to the need for expanding industrial and commercial sectors, but that commercial developments often are combined with huge residential projects and the net gain is minimized.