Cabooses, also known as cabin cars, traveled on the Pennsylvania Railroad at the rear of freight trains and served as office, workshop, observation platform, and living quarters for the crew. The cabin car was the domain of the rear brakeman and conductor. The brakeman monitored brake pressure and watched through the cupola window for sparks or smoke that could signal wheel or bearing problems. The conductor kept paperwork on cargo loaded and unloaded at each stop so the railroad could bill its customers accurately. The crew also used the cabin car as a dormitory and stored tools, spare parts, and emergency equipment there. The Class N5b model was introduced in 1937 and was based on the N5, built in 1914 as the world's first steel cabin car. The Class N8, launched in 1950, was the last cabin car designed by the Pennsylvania Railroad and was three feet longer than the N5a.