Engines were then built especially for switching. Their outward appearance was generally that of road engines minus leading and trailing trucks, which were not needed to guide the drivers at the slow speed used in this type of work. Since they were never far from the round-house, the early switchers were tank-engines. The limited coal and water supplies became an irksome feature as business increased. Consequently, later designs included separate tenders of ever-increasing sizes. Imagine if you can, a yardmaster with a road engine and crew waiting for a train to be made up,another train entering the yard and the switch engine needing water and/or coal. The later switchers could work an eight-hour shift on a tank of water and go two or more days on a tank of coal. Today's diesels average about three days on a tank of fuel oil.