What a great picture!
I believe that this is a bridge orbweaver/grey cross spider (Larinioides sclopetarius) or a close relative. The common name "bridge orbweaver" refers to this spider's preference for building webs on bridges and other steel structures.
Furrow spiders (that's a common name for this genus) belong to the orbweaver family (Araneidae) of spiders. No species of orbweaver is recognized as being dangerously venomous.