During the Second World War, a number of trolleybuses were borrowed from other systems, to cope with heavy traffic, but the use of electric vehicles ended in 1957.
In 1898 it was sold to the British Electric Traction Company, but their attempt to get local authority approval to extend and electrify the line failed.
The tramway closed unexpectedly in February 1902, when an outbreak of the infectious disease glanders resulted in most of the horses dying.
In Pontypridd, work began in July 1903, and in August, they were able to use their statutory powers to buy the horse tramway.
although the actual sale did not take place until 11 October 1904, when British Electric Traction received £5,750 for it, after which it was divided between the two councils, with the change in ownership occurring at Trehafod.
Progress on the new line was good, and the first trial runs were made on 12 February 1905, with an official opening scheduled for March.
[5] Where the trolleybuses crossed the River Taff, the trolley wires were supported by two semi-circular cross-arches, which were adorned with decorative ironwork.
At the Cilfynydd terminus, a turning circle was provided, to prepare the trolleybuses for the return journey, but at Treforest they just reversed into a side street.
This was scheduled to occur on 31 October 1956, but had to be postponed due to delays in the purchase of replacement motor buses.
[7] The closure of the system was not announced publicly, since the sale of the vehicles had already been agreed in principle, and the company did not want souvenir hunters removing small items from the trolleybuses.
[11] Pontypridd owned a total of 17 trolleybuses during the life of the system, and borrowed eight vehicles during the Second World War to cope with high traffic levels.