A field study was conducted to record observations of 41,744 market-weight pigs upon arrival at a commercial abattoir to evaluate the relationships between various independent factors and open-mouth breathing, skin discoloration, lameness, unloading time, and mortality during transport. Observations were recorded from 242 trailer loads on 46 separate days over a period of 14 mo. Travel time (<2.5 h or ≥2.5 h), wait time before unloading (<20 min or ≥20 min), loading pressure (<260 kg of BW/m2 trailer floor space or ≥260 kg of BW/m2 trailer floor space), ambient temperature while unloading (<17°C or ≥17°C), and trailer type [potbelly (PB); straight-deck with conventional unloading doors (SDC); or straight-deck with wide unloading doors (SDW)] were recorded for each load. Open-mouth breathing was more prevalent in pigs when transported on PB trailers compared with that of SDC or SDW trailers, and at warmer temperatures (≥17°C). Skin discoloration was more prevalent among pigs unloaded at temperatures ≥17°C. Lameness was more prevalent after shorter travel times at greater loading pressure compared with shorter travel times at decreased loading pressure. Unloading time for PB trailers was longer than for SDC and SDW. Mortality rates during transport were minimal (0.06%) in the deliveries that we observed, and there were no significant relationships between mortality and any independent variable tested. Wait time before unloading was not associated with any of the dependent variables included in the statistical model. In conclusion, warmer ambient temperatures (≥17°C) and the use of PB trailers are associated with an increased incidence of open-mouth breathing and skin discoloration, and longer unloading times after the transport of market pigs.