highways.gov.uk/news/articles/15071450.htm
A plastic bridge ■■? ha ha 
Not exactly a new idea, although it might not have been done on quite this scale. Googling for “Plastic bridge” brings up a number of links:
hq.usace.army.mil/cepa/pubs/ … tory10.htm
Glad to see you read the news. i’m sure the people that thought about this bridge have looked at the risk of fire,and done thing’s to ensure it’s safe. 
TBH they’ve built bridges from wood for millenia and steel cable suspended bridges for a couple of hundred years and concrete ones for decades.
If you have a fire under any of those they can soon become knackered.
Wood obivously burns! Steel cables sofen with heat and stretch/snap and Concrete crumbles, even explodes with heat!