The Halo is a driver crash-protection system used in open-wheel racing series, which consists of a curved bar placed to protect the driver's head. It was developed following some high-profile fatalities due to head injury, including that of Jules Bianchi at the 2014 Japanese Grand Prix.
At the 2017 British Grand Prix, an alternate safety device was tested on Sebastian Vettel's Ferrari. The Shield was a strong windscreen that looked similar to what would be used on a fighter jet. Vettel was the only driver to test the system, completing a single lap with the device. He complained the device distorted his vision and caused him to feel dizzy.
The Halo was introduced on all cars for the 2018 Formula One Season and has since been adopted by a variety of open-wheel championships.