The Railway Procurement Agency is considering extending Luas trams to up to 52m in length.
However, the agency is less sure about using other new developments in tram manufacture to avoid overhead wires in architecturally sensitive areas of Dublin's inner-city such as near Trinity College and College Green.
The agency, which is currently converting its 30m Red Line trams to 40m, said peak-time capacity problems on the Green line and increasing demand meant new trams would need to be longer and run more frequently.
With 58 trams in use or on order for the existing lines and a further seven new lines proposed under Transport 21, the Luas order for new trams, taken together will be one of the largest tram orders in the world.
An agency spokesman said it had not as yet determined how many new trams would be required. But French company Alstom - manufacturers of the current Citadis tram in use in Dublin - confirmed the order could be one of its largest.
Recent developments in the building of Citadis trams have eliminated the raised floor areas, giving a complete low floor tram which is slightly longer than the original trams.
This means the new trams would be 52m long while extending existing trams would result in 50m sections.
However, while the agency is interested in longer trams a spokesman appeared to pour cold water on other new developments, such as the use of "flywheels", batteries or underground power supplies.
An underground power supply has been used by Alstom in Bordeaux and Nice in France where the city authorities did not want to put up overhead wires. Other options developed by Alstom include a "flywheel" which can power a tram over a short distance.
The agency spokesman said the difficulty with buying new trams with batteries or flywheels was that all existing trams would need to be converted and using an underground power supply was significantly more expensive.
