More than 280,000 students rode about 3,300 buses more than 40 million miles to schools last year in and around Washington D.C.'s sprawling suburbs.

In Virginia, school officials in the Alexandria, Arlington, Fairfax, Loudoun and Prince William school districts spent more than $32 million to run their transportation departments. In Maryland, the Howard, Montgomery and Prince George's school districts spent more than $48 million to run their transportation departments.

In the Fairfax County school district, the area's largest, an average of 87,314 pupils road 912 buses daily more than 11 million miles last year. Fairfax's transportation budget was $20.3 million.

In the Prince George's system, the area's second largest, about 70,000 students rode 730 buses 11.8 million miles last year. Prince George's $24.2 million transportation budget was the largest last year among the counties surveyed.

Maryland school districts are required to replace buses every 10 years, said Christopher Carter, a spokesman for the Maryland Department of Education. In Virginia, there is no specific replacement requirement, although buses usually are replaced every 10 to 12 years, said R.A. Bynum of the Virginia Department of Education. However, Bynum said, the Virginia Board of Education is considering a replacement policy that would set specific guidelines. -- County -- Pupils daily -- Buses -- Pupil cost -- Budget* -- Miles

HOWARD

1983-84 15,887 163 $188 $2.9 million 2.2 million

1984-85 15,359 158 205 3.1 million 2.4 million

1985-86 16,750 163 230 3.8 million 2.5 million

1986-87** 17,525 168 242 4.2 million 2.6 million

MONTGOMERY

1983-84 54,374 730 295 16.0 million 10.7 million

1984-85 54,492 753 332 18.0 million 11.3 million

1985-86 57,977 769 330 19.1 million 11.6 million

1986-87 58,976 794 324 20.0 million 12.2 million

PRINCE GEORGE'S

1983-84** 68,000 686 157 20.9 million 11.2 million

1984-85 70,000 686 172 21.0 million 11.5 million

1985-86 69,000 686 191 22.0 million 11.7 million

1986-87 70,000 730 204 24.2 million 11.8 million *The districts' operating budget includes money for maintenance, salaries and other costs incurred in running a transportation system. **Estimated costs.