Minecraft furnace railway

I'm playing on an island style map, and i made a railways from my island to a mainland to find more supplies. I already built the rail way, but i don't have nearly enough gold to get it working with power rails, so i'm resorting to furnace carts. When i try using the furnace, sometimes i send it rolling off without me, is there a way to make like a lock or something to catch the cart in case i'm not on?

I'm not good with redstone so there might be a better way, but what i do is have the cart placed on the first rail, then i leave the second rail un placed until i'm in, then i place it, you could have a chest with the rail there or an item frame for when you want to use it i don't know