Once there were a few big machines and Norman Bate (Who Built the Highway, etc.) was their Boswell; now there are many, each a specialist in a technological system, no longer a familiar friend--but kids are still curious about them. Mr. Saunders, fresh from Building Brooklyn Bridge, describes the role and operation of each in a format reminiscent of Date but without any of the latter's personalization. The division of labor is exemplified by the leaf-sucker-up, the street sweeper and the street flusher in the fall (supplemented by the sewer cleaner); by the snow plow, sander, snow blower, snow loader and snow melter in the winter, by various cleaner-uppers in the spring. With the first warm weather, road building begins--here's how from the bulldozer clearing the ground to the concrete paver or tar spreader and line painter;all year round garbage has to be collected, which fills the last section. A succinct, direct text and strong but adequately detailed illustrations do well by a well-liked subject.