sentences:  The trains as a result became heavier, so the AB locomotives were accordingly replaced by the newer, more powerful locomotives of the K and then J classes, followed by the JA class in the 1950s.Despite the heavy demand for services, the Railways Department cut the "Rotorua Express" to run just thrice weekly each way in January 1944 because of coal shortages.This harmed demand, and when additional economic difficulties led to the service being further reduced to just twice weekly in 1951, patronage plummeted in favour of the more regular bus service operated by the New Zealand Railways Road Services.Nonetheless, the "Express" continued to operate almost until the end of the 1950s, when only 6,342 tickets were sold in Rotorua, in contrast to 35,554 in 1929.