On a run this week, I passed Barnes Bridge (above) and then Hammersmith Bridge just as scaffolding was being dismantled - the workmen were also taking down the three bales of straw that had been hanging underneath the bridge whilst repairs were taking place. The man in charge told me that Thames byelaw 29, dating from the 1700's, requires that a bale of straw be hung from any bridge reduced in headroom as a result of repairs. Straw is used so that there will be no damage to any boat or person hitting the bale.
River Byelaws 1978 (as amended) - Part 5
Bridges
29.
(1) When the arch or span of a bridge is closed to navigation the person in control of the bridge shall suspend from the centre of that arch or span -
(a) by day, three red discs 0.6 metres in diameter at the points of an equilateral triangle with the apex downwards and the base horizontal;
(b) by night, three red lights in similar positions to the discs displayed by day.
(2) When the headroom of an arch or span of a bridge is reduced from its usual limits but that arch or span is not closed to navigation, the person in control of the bridge shall suspend from the centre of that arch or span by day a bundle of straw large enough to be conspicious and by night a white light.
It also seems that this warning dates back to Roman times. Makes you wonder what the Romans ever did for us ...
Below is the bale destined for the Blackfriars Bridge renovation project.
I also found another great river image when researching straw bales on the Port of London site - three Port of London policemen engage in their annual life saving practice at West India Dock in 1930. Can't believe they stayed afloat or saved anyone with all of that gear on.
Its the second image under the people category -
http://www.pla.co.uk/centenary_galleries.cfm