Police are reminding driver to make sure the hood is latched firmly closed after filling the windshield washer reservoir.
The O.P.P. say a driver on the eastbound 417 had the hood of their car fly open near Terry Fox around 10 a.m. Friday.
The driver couldn't see so came to a stop in the left lane.
That set off a chain-reaction crash that involved two other vehicles.
Three people were taken to hospital with minor injuries.