Rail Track Carriage Crabbing

Hi,
Hope someone can help, i have a bridge spanning an open rectangular tank with an end carriage either end running backwards and forwards along some rails either side of the tank. The natural movement of the bridge on the rails causes it to weave from side to side down the track and i'm trying to prevent it, the bridge is about 15metres long and weighs around 18 tons. I've already come up with a design using some jockey wheels mounted horizontally either side of the rail, however my project engineer will probably want a cheaper alternative.

Can anybody help with an alternative?

Sounds like a cheap enough fix to me...
There are a hundred ways to skin a cat. Without being there to see this thing and all its components... and the materials they're made of... one could only speculate...?