This year's Classic clashes with the Rouen Armada, a Tall Ships event, which is held every five years.
http://www.armada.org/In 2003 the event attracted 7 million spectators plus an additional 2 million along the banks of the Seine whilst the ships were arriving and, in particular, departing.
If you are returning from the Classic via Rouen on Sunday 13 July it might be worth bearing in mind that there is an Iggy Pop concert at 21:00 that evening, followed by a fireworks display at 23:00. Rouen quayside is likely to be buzzing well into the early hours that night.
This year's departure starts at 09:30 on Monday 14 July, Bastille Day, which is a public holiday. Traffic disruption around Rouen is inevitable, and the areas around the Normandie and Tancarville bridges will also be heavily affected during that day.