A V16 engine is a V-shaped engine with 16 cylinders. Engines of this number of cylinders are not in common in automotive usages. A V16 engine is perfectly balanced so long as its constituent straight 8 banks are perfectly balanced, regardless of the V angle. In simple terms, it does not require contra-rotating balancing shafts, which are necessary to balance engines with an odd number of cylinders in line or those equipped with counterweighted crankshafts like the 90-degree engines. In addition, the V angles of 45 degrees and 135 degrees give an impulse every 45 degrees, so they are optimal solutions for even-firing and non-split bearing crankshaft journals. V16 engines are rarely used in automobiles because of the demand for V8s or V12s of the same displacements typically produce just as much power and they are much less expensive to manufacture and maintain. The few V16s that have been produced were used in high-end luxury and high-performance automobiles due to their smoothness without many vibrations. Today, the most common applications for V16 engines are in railroad locomotives, marine craft, and stationary power generators.