carry the bike inside the vehicle. to summarize what others have said.
no additional cost.
no exposure to elements.
no danger of impact (cars bridges garages....)
greatly reduce the risk of theft.
you can buy a piece of carpet or a rubber mat to lay down to help keep the vans interior clean.
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2010 Kestrel RT900SL, 800k carbon, chorus/record, speedplay, zonda
2000 litespeed Unicoi Ti, XTR,XT, Campy crank, time atac, carbon forks