For the past two years I've been very fond of cycling.

Near the end of 2008 I started doing some occasional rides into work, and in January 2009 I bought a newer road bike to follow up on that. I did around 6000km that year.
During 2010 I did even more riding but had to end at about 6500km. This was due to the fact the I have gotten an outside job at the company I work for. They gave me a car to ride and sent me to a company about 50km away from home, and I was only used to 25km rides.

So here I am, 50km away from home, posting about my next step in commuting. During the upcoming weeks I need to get back into shape so I can ride to work again. Next to the commuting I have signed up for the "Ronde van Vlaanderen" this April. So I need to get into shape to ride that as well.

I haven't ridden my bike for 3 months now. Am I safe to hop on and do the 50km ride twice a day?

Any ideas on how to do this? Just get on the bike and do it, or start off slow?