Design advances of air compressors for buses and trucks are reviewed. Volumetric delivery, supplied pressure, and heat removal are discussed in detail. Results show that the single-cylinder air compressor with a delivery of 500 1/min at 10 bar will retain its dominant position in industrial use for years to come. Present design limits displacement to about 300 cm3.New designs of valve-plate cooling have raised previous limitations of compressor performance, which may be necessitated by increased use of compressed air for auxiliary purposes. Single-stage delivery can now provide 20 bar, and replacement of ring plate valves allow compressor speeds above 3000 rpm. Operating temperature improvements are discussed in terms of various heat-transfer mechanisms, integrity of seals, and lessened carbon deposition in the oil line. Several variations of the new design are presented and performance characteristics are compared to conventional models.