Honolulu is the fourth-most traffic-congested city in North America, according to the third congestion index by navigation device-maker TomTom.

The index compares travel times during congested periods, to times of day when traffic is flowing freely.

Traffic is worst in Los Angeles, Calif., and Vancouver, Canada, each with a 34 percent congestion level; San Francisco was ranked third at 33 percent; Honolulu was No. 4, at 31 percent, and Seattle was No. 5, at 27 percent.

The index measured traffic congestion in 57 metropolitan areas between July and September of 2012, based on real travel time captured by in-vehicle TomTom devices.

The full index is posted online www.tomtom.com/congestionindex .