The list author says: "We had a hand-me-down Brio train set and we later got Duplos, so I looked for a way to make them compatible. This is what I found, and allows for the most creative and least frustrating play! If you are starting from scratch, I recommend sticking to Duplo blocks and trains and not getting wooden trains because everything will be compatible automatically and Duplo has more building options."
"Lego makes the highest quality plastic bricks you can buy, but you do have to pay for that quality. This set will give tons of options in play. It's pretty easy to find sets of used blocks on craigslist or ebay."
"All the Mega Bloks Thomas the Train cars are compatible with wooden tracks. The wheels run on the wooden tracks AND between the bumps on Duplo/Mega Bloks bricks, and the tops are compatible with Duplo and Mega Bloks, making this a great addition for combining your plastic bricks and wooden tracks! Most Duplo trains and cars are NOT compatible with wooden tracks. (except for the "runner" sets)"