I had posted another picture of the same action - Tsujimawashi or Float Turning. I thought this was a better one because of the colours.
From the Gion Matsuri Volunteer website:
This picture depicts the “Tsujimawashi” . To enable the hoko to turn more easily when going round corners, wet bamboo is laid under the wheels. The float is then pulled almost on a 90 degree angle right angle to make it slide on the wet bamboo and change direction.