There are multiple artists with this name:

1) Traffic were an English rock band.

2) Traffic is a poprock band from Estonia.

1) Traffic started out with Steve Winwood, Dave Mason, Jim Capaldi, and Chris Wood after Winwood left The Spencer Davis Group. From their beginning, in 1967, they were quite popular in their native England, though success elsewhere was slower in coming. Their first three albums combined psychedelic rock and soul with elements of British folk music, giving them a unique, groundbreaking sound. Their most popular single was Dear Mr. Fantasy, from the album of the same name.

Traffic reached a much wider audience when, on the dissolution of Cream, two thirds of that band, one third being Eric Clapton, joined Steve Winwood (during a temporary Traffic disbanding) to form Blind Faith, which also included future Traffic member and sometime Family man, Ric Grech.

In 1970, after the disbanding of Blind Faith, Winwood set about recording a solo album. After Chris Wood and Jim Capaldi became involved, the decision was taken to release this album (eventually what would become John Barleycorn Must Die) under the Traffic name, despite the absence of Dave Mason.

Around 1971, Mason left for good (having been in and out of the band from the beginning), and the the band experienced a variety of personnel changes. The resulting band added some jazzy elements to their style, pioneering the jazz-rock genre, and the compositions tended to stretch out over longer lengths. With their albums The Low Spark of High Heeled Boys (1971) and Shootout at the Fantasy Factory (1973) their popularity in the US grew. After two more albums, personnel problems resulted in the band calling it quits (but for a brief reunion in 1994 without Wood, who had died in 1983). Winwood, Mason, Capaldi, and Wood all pursued solo careers, with Winwood garnering the most success.

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