In vehicles equipped with abs, the driver's foot must remain firmly on the to activate the abs.

The driver’s foot must remain firmly on the brake pedal to activate the ABS.

An Anti-lock Brake system (ABS) is an effective braking system if used correctly. It simply keeps the foundation braking systems from locking up. It allows the driver to maintain directional stability and in some cases, reduces stopping distances during emergency situations when a driver slams the brake.
The foot of those drivers in vehicles equipped with ABS should remain firmly on the brake pedal, allowing this system to automatically kick in. In case of a slippery road or a panic stop, an Anti-lock Brake system prevents wheel lock up and helps your vehicle maintain a straight line