B.C.'s Transportation Minister Mary Polak says increased truck traffic on the Pattullo Bridge isn't due to drivers using the route to avoid the tolls on the Port Mann Bridge.

Pattullo and Port Mann bridges

"We are not seeing a decline in the numbers on the Port Mann Bridge," said Polak on Thrusday.

Polak was responding to concerns raised by some Metro Vancouver mayors who claim truck traffic on the Pattullo has gone up 25 per cent and are calling for a regional good movement strategy.

The minister said more work needs to be done to understand why the congestion is getting worse and her ministry is looking into the issue.

"There are any number of reasons, the least of which is trucks avoiding other routes with congestion, but also increased economic activity can drive that," said Polak.

In 2010 Translink said it plans to replace the aging Pattullo Bridge by 2015, but warned tolls could be used to pay for the $1.2 billion price tag.