Families on Osney Island in west Oxford face a summer of disruption, as heavy machinery is hauled through narrow streets for a lengthy repair programme at the nearby lock.
Pile-driving equipment was being brought in on June 6 in preparation for the work, which will continue into the autumn.
To allow large vehicles to gain access to the Environment Agency's depot, Bridge Street residents were forced to move their cars by 7am.
They were not allowed to return until 6pm and warned that if they ignored the order they could face fixed penalties or have their car removed.
But this morning, a few cars remained and machinery drivers managed to work around them, causing some residents to accuse the agency of overreacting.
Retired electrical engineer, Tony Roberts, claimed the agency could have arranged alternative access to its depot via the Osney Mead industrial estate.
He said: "Two vehicles have gone down the street with no trouble, between cars still parked there."
The Environment Agency said parking restrictions would be in force again on June 13, and on six more days between July and August.
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