Actually, yes they do.
Not 18 wheelers per se, but last year alone their were 46 seperate Refinery fires an explosions -- an average of FOUR A MONTH.
Oil well blowouts happen on a fairly regular basis also, they just don't usually explode because the fail safes work.
Can you please post a source? When I researched this I got very different numbers (more like one disaster every few years)