The objective of this project was to provide pertinent information on the performance of refrigeration and heating transportation units to help fleets make decisions that will improve efficiency and increase productivity. To achieve this objective, tests were designed to measure the performance of selected refrigeration and heating units, mounted on refrigerated and heated van semitrailers. Cooling and freezing tests were carried out in summer conditions while heating tests were carried out in winter conditions, for various temperature settings. Two fundamental approaches were considered: the design of the refrigerated or heated trailer and the temperature setting of the refrigeration or heating unit. For cooling and freezing tests, the fuel consumption comparison between similar trailer models of different ages showed that newer units performed better than older ones. However, other factors such as trailer design, presence of a ventilation system, and type of insulation may also influence fuel consumption of such units. For refrigerated trailers of the same make and of similar age, those with swing doors performed better than those with roll-up doors with regards to both fuel consumption and insulation. For trailers with the same make of refrigeration unit, those without side doors performed better than those with side doors. For heating tests, it was observed that newer heated trailers with composite or insulated doors generally consumed 1.5 to 3 times less fuel then the older trailers with wood or metal doors. The tests confirmed that the interior temperature setting has a significant impact on the fuel consumption of the refrigeration or heating unit when the difference in set temperature is considerable.