Entering Canada via the Rainbow Bridge it was straight across, pay the toll a quick look at passport, stamp, and a cheery wave through and the second occasion they didn't stamp it again.

Coming back both times it was double check documents, not only passport but car hire documents but kept waiting for no longer than five minutes though.

Have not experienced the Peace Bridge but the satellite only shows about 16 vehicles in 4 separate rows at Fort Erie and about the same at Buffalo.

Guess some periods can be busier than others and satellite images are fixed moments in time though!