All of these engines were nine cylinder rotaries. The main difference between the two prototypes was in the engines, both fully cowled rotaries. By the mid 1950s, construction of traffic circles and rotaries had ceased entirely. Rotaries typically feature high speeds inside the circle and on the approaches. Limited constructed the flyover part including two elevated rotaries for BRTS. This article follows that convention and refers to other types as "traffic circles" or "rotaries". Rotaries generally have high compression ratios, making them particularly suitable for the use of HCCI. Rotaries of newer construction are either diesel- or electric-powered. The favourable power-to-weight ratio of the rotaries was their greatest advantage. This is a list of rotaries in the state of Massachusetts in the United States.