Several tram lines are experiencing delays after a tram and a van driven by a P-plater collided in Melbourne's CBD around 11am on Wednesday morning.

Route 11, 12, 48 and 109 trams to St Kilda and Port Melbourne are affected.

Convenience and service quality are vitally important - and for public transport there is no shortage of improvements needed: more frequent services, better connections and infrastructure, relief from crowding, better reliability.

There are no reports of serious injuries.

Yarra Trams is diverting some trams via La Trobe Street.

A spokesman for Yarra Trams said trams resumed along Collins Street from 11.30am and the timetable will be back to normal as soon as possible.