Air conditioning school buses used to mean opening windows, which on a hot day simply let in hot air. Now more and more states and school districts are finding that painting the tops of school buses white makes the ride cooler.

The paint job may also make riding on school buses safer.

That conclusion was suggested by the response to a recent pilot program in North Carolina in which repainted buses were used. Motorists reported that white-topped, orange-bodied buses were easier to see.

As a result of the program, North Carolina will give school systems the option of specifying white tops when ordering new buses, said William Turner, an assistant superintendent for transportation at Brunswick County Schools. Buses with white tops cost a few hundred dollars more than regular buses, manufacturers say.

Part of the program involved studying the effect of the white tops on the temperature inside the buses. Digital thermometers were mounted on county school buses and readings were taken four times a day from August to December. The buses were tested while running and while parked.