I always assumed a 1.5 ton vehicle imparted the same weight on a bridge regardless of wheel and suspension type.

Different tires could have obviously different effects on wear/tear of the road/driving surface...but that shouldn't have anything to do with a bridge's structual integrity.

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I'm like one of those idiot savants...well, except for the savant part.
"In order to increase awareness of the homeless, security have been given binoculars."