I heard on the news a few days ago, a road in WI buckled up because it was so hot.

[hunter]

14. I saw this happen in Illinois...

...except one slab crumpled under the other, making a stair-step facing traffic. We were traveling on the other side of the interstate.

About a dozen cars hit the raised slab before traffic came to a stop. These cars were totaled and were facing in all directions surrounded by mechanical debris. Fortunately nobody was killed.

The expansion joints are designed to compensate for a certain maximum temperature. Once that temperature is exceeded the road buckles.

But there's a consideration limiting the size of expansion joints too. The larger the expansion joint is, the more likely it will fail if water gets in between the joints and under the road and then freezes. Freezing water will also cause roads to buckle.

These freeze-thaw cycles can also move entire sections of road, sometimes pushing adjacent slabs closer together, making the expansion joint smaller, and lowering the temperature at which the road will buckle in the summer.