A position code is recorded by capturing a sequence of images while writing on the base with a user unit. The opening is disposed at an axis collinear with a longitudinal axis of the noise producing element. The sharp-bottomed grooves produced in the concrete by the rim are preferential fracture sites, so that, after the wall slabs have been removed, the concrete portion overlying the isolation pocket can easily and cleanly be broken out. The wheel surface may be engaged by brush elements that have a length that changes cyclically and the brush elements may also cyclically vary the contact pressure between brush elements and the vehicle surface. A frontmost end tube 31 and a basemost end tube 32 disposed in a frontmost end portion and a basemost end portion of the core wire 10 respectively are fixedly attached to the core wire 10.