Liverpool's Car Free Day was ended two hours early after major congestion formed in parts of the city.
The Strand was supposed to be shut between 10:00 and 16:00 BST in an attempt to encourage drivers to use alternative modes of transport.
But it caused traffic jams in other parts of the city centre as vehicles were diverted away from the waterfront.
Pablo Paca told BBC Radio Merseyside "most of town" had been at a standstill with traffic.
Council officials decided to reopen the closed route at about 14:00.
The bid to get drivers out of their cars sparked criticism on Twitter, with people describing the initiative as "disastrous".
One driver tweeted: "It's not car free, the cars have just gone a different route and caused more congestion.
"All that money to improve The Strand and then close it when people are trying to get to work."
Another added: "Absolute disaster for people trying to access businesses and services.
"Nearest buses at Queens Square for most as bus routes disrupted/diverted, so it is annoying a lot of people."
Liverpool City Council was contacted for a comment after thanking people for their "patience" in a tweet.
#Traffic update: The Strand is now in the process of reopening.
Thanks to all who supported #CarFreeDay – despite the poor weather!
We know some will have had a longer journey today & we appreciate your patience.
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