Iowa Department of Transportation is promoting the use of discarded tyre shavings to fill expansion joints in its bridges following successful field trials. Previously the US state had used foam blocks which were tending to come loose and float away leaving gaps of 100mm or more between the deck and roadway. The tyre shavings are heavier than water and are not a significant hazard if they do become dislodged. They are a by-product of the tyre retreading industry and would otherwise be sent to landfill.