About as serious as it gets.
It took 12 hours for police and fire officials to finally reopen all of the lanes on a section of the New Jersey turnpike on Tuesday after a dump truck somehow managed to overturn while driving under an overpass. Sadly, the driver was killed. The exact cause of the crash is still being investigated and traffic was stopped in both directions. The accident occurred at around 10am but it wasn't until after 10pm when everything was re-opened. The smoke from the crash site could be seen for miles.
Police also tried to get the message out quickly to warn drivers to stay away. It wasn't only the crashed truck that caused concern, but also the stability of the overpass itself. Its support beams had to be inspected by engineers to make sure they weren't compromised by the heat from the fire.