The 75 new trams that the Coalition has promised to buy in its next term will spend most of their time sitting in traffic unless a serious effort is made to speed up Melbourne's tram network, one of the world's slowest, a transport lobby group says.

Melbourne's trams have an average speed of 16km/h, dropping to just 11km/h in the CBD.

A tram makes its way through heavy traffic on Sydney Road, Brunswick. Credit:Craig Abraham

Industry group Tourism & Transport Forum said the government would get more value out of its promised new trams – costed at $1.07 billion – if it made the tram network more efficient.

"Melbourne's tram network is one of the city's great assets but its potential is not being fully realised," forum chief executive Margy Osmond said.