‘Intrusion bars’ are the additional parts of the roll cage added to a formula car chassis to help protect the driver during a crash. The idea is to have extra protection against foreign objects intruding into the cockpit. Vintage Formula Fords did not come with them, and are still not required in vintage or historic racing. They are the upper horizontal bars between the main hoop and the forward hoop, and are required in SCCA FF racing. Modern Formula Fords also come with Kevlar lined body work for additional intrusion protection. Here is a picture of the intrusion bar addition we have completed on my Crossle Club Ford, and I’m planning on some education into further safety ideas like Kevlar bonding and EPS-bead custom seats (motorcycle helmet liner material).