Turns out that TransLink provides weekly updates on the Pattullo Bridge traffic counts – with some attractive charts if you’re into that kind of thing:

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Pattullo count

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And if you are, there’s plenty more where that come from – here.

Upshot: There’s lots of variation in the counts, but overall, traffic seems to be up 5 to 7 percent post Port Mann Bridge opening.

That’s probably a small but perceptible change to drivers, given that the use of bridge is maxxed out at rush hours.  But not high enough to suggest the leakage will have a negative impact on the expected numbers for Port Mann – unless there’s been a drop-off of traffic crossing the Fraser.