If it's a light rail system and not a tram that's under construction from Gungahlin to Civic, why are there now 'T' traffic lights at our intersections?

Is it because it's a light trail system, where the 'T' is silent, as one meme suggests?

Will it be called the tube, or the trolley, as it is in other places around the world?

Intrigued as we are with all things light rail, The Canberra Times did a quick ring-around to figure out why - and the answer sadly didn't involve any silent letters.

"I had to look into this actually. It's specified in the Australian road rules, whether it's a tram or light rail, the [traffic light] symbol is a 'T'," the Australasian Railway Association's general manager of passenger and corporate services Emma Woods said.

'T'-lights are also used on the Melbourne and Gold Coast light rail systems, she said, and are similar to the B-lights we see in dedicated bus-ways, like that on Barry Drive.

ACT government sources also said 'T' had been used as it's the universally recognised symbol of rail systems, whether light or heavy.

But what is the difference between a tram and light rail system?

"Tram is your historic or more traditional version, the difference being they run on the road along with traffic. That's your Melbourne system for example," Ms Woods said.

"Melbourne has the largest tramway in the world at 250 kilometres, but also the slowest because it's stuck in traffic like everyone else on the road.

"Light rail is the modern version and it has a dedicated corridor. It doesn't get stuck in any road congestion, it has higher travel speeds. Some people use the terms interchangeably but realistically Canberra is getting light rail."

The Gold Coast system also has its own dedicated corridor, although the Newcastle system also under construction shares the road with cars in one stretch.

Ms Woods said having a dedicated corridor for light rail, like in Canberra, made the network more efficient.

"Melbourne has a really substantial investment program under way to transition from a tram way to a light rail system, meaning they're sifting to a dedicated corridor which increases the speed and the number of people it can move," she said.

Light rail is expected to start running from April 27, with testing under way on the Northbourne end of the line.

Drivers have also been undergoing training on the Northbourne corridor, with signs warning of changed traffic light sequences due to testing.