In modern diesel and electric locomotives, the bathroom (often called the "head") is typically located inside the "nose" or the short hood of the engine, directly ahead of the engineer's cab. Access is usually through a small, heavy door near the floor level. These facilities are notoriously cramped and functional, often consisting of a stainless steel chemical toilet similar to those found on small airplanes or buses. In older or smaller switching locomotives, there may be no bathroom at all, requiring the crew to wait for a stop at a yard office. In newer, high-tech engines designed for long-haul freight, the bathrooms are more likely to be modular units with improved ventilation and lighting. Because locomotives can be in operation for 24 hours or more without the crew switching out, having a dedicated on-board toilet is a critical part of the cab's ergonomic design, though it is a far cry from the spacious restrooms found in the passenger cars further back on the train.