When does a walk to school that's potentially dangerous for elementary school pupils become safe enough for intermediate and high school students? And once you identify a seemingly safe route for older children to use, how do you make sure they follow it?

These questions will be addressed this morning by Fairfax County school officials, county supervisor Audrey Moore and parents in the Rutherford area as they walk a route youngsters will be asked to use next fall on their way to Robert Frost Intermediate, 4101 Pickett Rd., and W.T. Woodson High School, 9525 Main St., in Fairfax County.

The 10:30 a.m. walk, beginning in the Frost parking lot, is designed to resolve a conflict over a school system decision to eliminate bus service next fall for children attending Frost and Woodson from the Rutherford and nearby Mantua neighborhoods. The decision affects nearly 700 youngsters. a

"I have not wanted to mislead people that their children won't walk," said Moore, who along with school board member Eltse Carter called the meeting. "But parents are entitled to se with their own eyes what the school administration is providing. We have an obligation to assure ourselves it's safe," she said.

More than 400 residents in Rutherford, between Little River Turnpike and Braddock Road, and 200 residents in Mantua, between the turnpike and Arlington Boulevard, have signed petitions protesting the bus cuts because they believe the walking routes recommended by the school system are too hazardous.

But school officials maintain that new sidewalks and the use of crossing guards make the walking path as safe as any other used by Fairfax County students.

The route for the Rutherford children takes them across Olley Lane to Little River Turnpike or Pickett Road, where the schools are located. Mantua children will be asked to walk to Briary Way, cross Little River Turnpike and walk along the turnpike to Frost or Woodson.

"There is no question this would not have been a route that would have been authorized for elementary age youngsters," said school board chairman Ann P. Kahn, whose district includes Mantua, "but when we are dealing with intermediate or high school youngsters, if they cannot abide by a red or green light plus directions from a crossing guard, I don't know what else we can do to safeguard their lives."

Charles Dolinger, Area II administrator for the county schools, said a decision was made to drop 16 bus routes in both neighborhoods after school safety officers, transportation supervisors and Fairfax police determined that sidewalks and other improvements in the area made the route safe for walkers.

Dolinger said the decision was based on county school board policy, which states that busing will not be provided for intermediate and high school students who live within 1 1/2 miles of school and can walk along a nonhazardous route. At an annual cost of $3,500 per bus and the same cost for crossing guards, cutting 16 buses and adding two crossing guards will save the schools $49,000 next year, he said.

In the Rutherford area, parent leader Zoa Mattox said parents believe the school board "is putting money ahead of safety." They are worried, she said, because children will be tempted to dart across traffic on Olley Lane to get to sidewalks on the other side. Another concern is that children will have to walk to school in the dark on early winter mornings, she said.

Mattox said Rutherford parents want the board to restore bus service to the neighborhood or to add crossing guards on Olley Lane, a hilly, two-lane road.

Similar complaints were voiced by Mantua parents, who fear that children will take a shortcut and cross the heavily traveled Little River Turnpike at Pickett Road, instead of at Briary Way, where a crossing guard will be stationed. "There is a light at Pickett, but tank trunks from the Fairfax Tank Farm go whizzing through there," Mattox said.

If children cross the busy highway and don't follow the recommended route, "Yes, indeed, their lives are at stake," Kahn said. "But these are not babies. We presume these youngsters are old enough to abide by rules and regulations."

Kahn said she hopes to settle the Mantua issue with a letter she mailed last weekend to nearly 200 residents who signed petitions opposing the bus cuts. She said she wrote that the problems listed in the petition are not valid and she is confident the route "is safe and comparable to others in the county."