I had a bike once. Single speed, "hard tail."
My brother, his friend, and I were going to go riding around this construction site. To get there, we had to go on a short stretch of road between my house and the site. Speed limit: 55.
We pulled out on the road, and my brother and his friend quickly pulled away. I tried to keep up, by my short little legs just couldn't do it. I pedaled harder and harder, faster and faster.
Then the handlebars started to get wobbly.
Then, they turned 90 degrees to the direction of my travel. My bike stopped.
I flew over the handlebars, catching myself with my face.
I busted my lip open, and was bleeding everywhere. My brother stopped, ran back to me, threw my bike in the ditch, and dragged me off the road to safety. A van stopped, offering assistance. We said we were fine.
My brother helped me hobble home.