The Prince William Board of County Supervisors voted last night to create a special transportation taxing district -- the second in the state -- to pay for a badly needed new highway in the county's eastern end.

Industrial and commercial landowners in the area between Interstate 95 and Dale City agreed to pay additional real estate taxes to finance the $40 million Prince William Parkway, which will run from I-95 past Potomac Mills Mall to the center of the county.

The eight-mile highway will relieve crowded east-west commuter roads and is expected to stimulate property values and economic development along its route. Without the landowners' contribution, the road probably would not be built until well into the next century.

After three years of negotiations, the owners of a majority of the industrial and commercial property in the 1,460-acre district petitioned the county to tax them an additional 20 cents above the regular rate, currently $1.36 per $100 of assessed value. Under state law, land zoned for residential use is exempt from the additional taxes.

The landowners, including developers Western Development, Lee Sammis and Cafritz Co., will pay additional taxes for 35 years, or until they have paid off 85 percent of the highway's cost.

The supervisors unanimously accepted the landowners' petition yesterday. "I think this {project} is an innovative public-private partnership," said Supervisor Edwin C. King. "I think we're going to have to have more of them if we're going to build all the roads we need to build."

Prince William County voters in 1988 approved a $25 million bond issue to pay the road's immediate construction costs. Using that money, Prince William officials broke ground about a month ago. The road will probably be completed in 1992, said Transportation Director Thomas Blaser.

"The voters provided the key" for the parkway, said Supervisor Kathleen K. Seefeldt (D-Occoquan).

Fairfax and Loudoun officials established the state's first transportation taxing district two years ago to pay for the widening of Route 28. The first segment of that project opened this fall.

That taxing district became controversial last year when the Fairfax Board of Supervisors reduced the amount of development that landowners were permitted to build on property in the district. The General Assembly overturned Fairfax's action last winter.

In Prince William, the supervisors agreed not to change the zoning on property in the district, except at the request of the landowners, for 15 years.

The road's $9 million interchange with I-95 proved to be a sticking point in the negotiations. The taxing district will repay 85 percent of the interchange cost, but the Virginia Department of Transportation will have to put up the money initially.

Without a state guarantee that it would build the interchange, the landowners' attorney, Curtis M. Coward, said the road would be a "$40 million parking lot."

State Secretary of Transportation John G. Milliken agreed to step in, and wrote a letter yesterday saying, "Though at this time it is not possible to commit specific funds to {the interchange}, the Department of Transportation will continue to explore alternatives for financing, including the use of federal funds."