as shaggy said..
its our motorsport body regulations..
any forward facing glass must have covering to stop glass shatter (stones, objects, accidents)
location of the battery must be indicated by a blue triangle (on the bonnet)
fire extinguisher must be securely fitted within reach of the driver
They only apply for Events that count towards series/pointscores and are approved for proper timing by the National Motorsport Regulatory body. Normal track days or private events are not so stringent.