A wide range of railroad employees labour to guarantee that passenger and freight trains arrive at their destinations on time and safely. Rail yard engineers, sometimes known as hostlers, move locomotives between tracks in order to keep trains organised and on time. They transport locomotives to and from maintenance shops, as well as prepare them for the locomotive engineer. Dinkeys are tiny locomotives used by some. Other railroad workers are concerned with train safety. Train cars are coupled and uncoupled with the assistance of brake operators. Signal operators are responsible for installing and maintaining communication signals along tracks and in the rail yard. Track switches in rail yards are controlled by switch operators to ensure trains move safely between tracks. Locomotive firemen keep an eye on train instruments and keep an eye out for risks on the track. The majority of rail employees work full-time. Because trains run 24 hours a day, many railroad workers work nights, weekends, and holidays. Rail firms normally demand a high school graduation or equivalent, and on-the-job training can range anywhere from a few weeks to several months, depending on the employer and the complexity of the job. Rail yard engineers, switch or signal operators, and yardmasters can all graduate to become conductors or yardmasters.