Protesters padlocked an access road and put up fences to prevent cars getting through after a child was almost knocked over by speeding traffic.
Belen Dilnot said campaigners from the group A Walk In The Park took action after four years of frustration.
Lime Tree Walk, which runs through Preston Park, Brighton, has a speed limit of 15 mph. It is open to disabled drivers and people who need access to the Chalet Cafe.
But parents said their children were at risk from motorists who ignored the restrictions and took advantage of an open access gate to speed up and down the road.
Mrs Dilnot said: "The park is being held hostage by irresponsible drivers and a council which hasn't got the will to make it safe for our children.
"Every day someone comes close to being knocked down. My child and myself have nearly been run over. Last week a child was thrown off his bike when a car nearly knocked him down. What is the council waiting for, someone to die?"
A spokeswoman for Brighton and Hove City Council said disability legislation required the gate to be left open so people with mobility problems could still enjoy the park.
She said the council was in the middle of a battle between A Walk In The Park campaigners and the Disabled Access Advisory Group, which had been campaigning to keep the road open.
Safety measures, including a disabled access-only sign, were due to be put into place in the next few days.
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