Motorists in Melbourne's bayside suburbs will spend more time waiting at level crossings as Metro increases the down time at dozens of railway boom gates.

Boom gates will lower as much as 15 seconds earlier each time a train approaches a level crossing on the Frankston, Werribee and Williamstown lines from this month, in preparation for the arrival of eight new X'Trapolis trains later this year.

Motorists will be forced to wait longer at train level crossings on bayside lines. Credit:Patrick Scala

The trains have faster acceleration than other trains operating in Melbourne, and Metro has made the change to avoid the risk of a road-rail smash.

In all, 46 level crossings and 33 pedestrian crossings will have their wait times extended.