The three bags of change fell from the truck at about 9 a.m. when it hit a bump in the 1900 block of Good Latimer, south of downtown Dallas.
The guard called police to help stop homeless people from taking the money as city workers brought shovels to scoop up all the coins that covered the street.
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One worker used a vacuum to help suck up the coins, which had also fallen into grass nearby.
Officers closed down the road between Hickory Street and Dawson Road for half an hour while the coins were picked up.