On Christmas Day 2012, a BNSF Railway Provo-Denver freight awaits a crew call in Utah Railway's Provo Yard. On the point is a General Electric ES44C4, with four traction motors instead of six. The center axle of each truck is unpowered, giving an A1A-A1A wheel arrangement. BNSF Railway was the first railroad to place an order for this model from GE, with more than 450 on the roster by the end of 2012. The ES44C4 features a computerized variable traction control system. When a variation in grade, traction, or wheel slip occurs, the computer adjusts the pressure to maintain sufficient adhesion, by varying the weight on the drive axles.
