More than 100 bus drivers were caught speeding in school zones in the 12 months to May, figures obtained under Freedom of Information laws show.
Police issued 428 speeding infringements to Transperth bus drivers and Transwa road coach drivers during that period.
The figure was 285 per cent, or 317 speeding fines, higher than those issued in 2009.
Infringements issued for speeding in school zones, which have limits of 40km/h at certain times of the day, made up almost 26 per cent of all speeding tickets issued to bus drivers. In the most serious offence, a driver was clocked at 25km/h over the limit outside Duncraig Primary School.
Transperth spokesman David Hynes said school zones were a trap for bus drivers because speed limits changed. "But they are professional drivers and they know this," he said.
Though conceding one infringement was one too many, Mr Hynes said the total number of infringements was manageable.
"Two-thousand five- hundred drivers covering about 80 million kilometres a year works out to about one infringement for every driver in 10 years," he said.
More than 64 per cent of bus drivers caught speeding had been travelling no more than 9km/h over the limit.
A further 152 drivers, or 35 per cent, were nabbed travelling between 10 and 19km/h over the limit.
In addition to speeding, 38 infringements were issued to drivers for running red lights. The speeding and red light offences combined racked up $86,800 in fines.
Demerit points issued to drivers of heavy vehicles such as buses are the same as for cars but the monetary penalty either doubles or is typically $100 higher than those issued to light vehicle road users.
The infringement notices are sent to Transperth in the first instance before being sent to individual bus operators, who identify the driver at fault.
Drivers pay the fines.
Eight notices were issued for failing to pay infringements on time, hitting three bus companies with an extra $1200 in fines.
Transport Workers Union official Paul Aslan said drivers were battling to meet tighter timetables because of increased traffic.
"The public want the buses there when they are supposed to be," Mr Aslan said.
"The drivers get abuse sometimes from the general public, but they do a great job overall."