Rail freight carrier Pacific National will study information downloaded from a trip recorder known as a ‘‘data logger’’ to examine how fast a coal train was going before it derailed yesterday morning at Clifton.About 40 freight and coal trains pass Clifton each day, with a speed limit of 80km/h.A Pacific National spokeswoman said the derailed train was going below the limit, but could not say how fast it was going until the data logger had been accessed.As residents of Wollongong’s northern suburbs know, coal trains are a regular sight, and sound, on the South Coast line, sharing the tracks with passenger trains during the night but prevented from running during peak hours.RailCorp, which owns and operates the rail network, said the derailment happened on a stretch where there was just a single track, meaning trains needed to wait for each other to pass that area.‘‘Freight trains are unable to access the RailCorp network before or during peak passenger times,’’ a RailCorp spokeswoman said. ‘‘The South Coast line is primarily for passenger services and they receive priority over freight services.’’The derailed train included 45 wagons filled with coal. Six of the wagons, each weighing 75tonnes when full, were left on the tracks as the line was cleared in the early hours of the morning.The train was transporting coal from Peabody Energy’s Metropolitan Colliery to the Port Kembla coal terminal for loading onto ships.Peabody Energy yesterday said it sends the vast majority of its annual output of 1.2 million tonnes of coal to Port Kembla, all by rail, with up to three trains a day making the trip from Helensburgh. RailCorp said there were many other freight trains using the line.‘‘Approximately 40 freight trains use that part of the South Coast per day, carrying a range of goods including coal, grain, flour and steel,’’ a spokeswoman said.‘‘Speed limits apply for freight trains and depend on a number of factors, including the geometry of the track and the number and weight of wagons on the train. ‘‘On a straight track the upper speed limit is around 80km/h, however this is rarely reached.’’A Pacific National spokeswoman would not comment on whether a broken axle was to blame for the crash, saying the company needed to perform a full investigation first.Pacific National runs five to 15 coal trains a week from Helensburgh to Port Kembla. Freight operators QR National, Southern ShortHaul and South Spur also use the South Coast line.Pacific National is owned by Asciano, which also owns stevedoring and logistics company Patrick.