I attended my first TT in 1957 as an eight-year-old. We had a coach tour of the circuit and I am sure I remember a broad painted line across the circuit in a few places. Their position and purpose were unknown, to the extent that I may have misremembered. However, while viewing a film of the 1950 Senior I noticed what appeared to be one of these lines at - I think - the Keppel Gate complex. Can anyone help?