[IronJack]

How often do bridges catch fire?

[ThunderSleeps]

Bridges over other roads always have to account for accidents and fire. Vehicles could simply hit the supports and catch fire. Accidents on the bridge could leak burning fuel through deck sections... Homeless people living under a bridge could set fires...

It's not that it happens too often, but you have to consider the consequences and expense if and when it does.

[Rebelbase]

Bridge fire pictures from google.

https://tinyurl.com/y6u6a7rt

[pierrem15]

Vehicles do underneath them. Even concrete and steel girder structures are susceptible if it’s a big enough fire (think tanker truck). Not sure if that’s more of a risk with these composites.