New solar powered flashing clearance signs have been installed at the Bayswater subway in an attempt to catch the attention of truck drivers.
Three trucks were caught under the subway in recent months having ignored the bridge's clearance height of 3.8 metres.
Public Transport Authority spokesman David Hynes said the new electronic signs had been installed on a trial basis to increase the awareness of truck drivers.
"The Bayswater subway is one that has probably been a higher profile truck vs bridge scenario than other subways in Perth," Mr Hynes said.
"Provided they know what their own clearance level is - hopefully it'll make a difference."
Mr Hynes said the bridge had been inspected after each incident and no significant damage had occurred.
"That's not to say that there might not be an incident sometime in the future where there is significant damage - or worse still where someone gets hurt.
"That's why we've done this. To bring it to the attention of truck drivers who might be passing through that way."
