You do, yes. But that can be a metal pin the size of your pinky finger. It's a super easy engineering challenge compared to the regular brakes that slow down the car, which, when emergency braking a 2 ton car from 100 mph, needs to briefly absorb nearly 1 megawatt. Thats the power used by 1000 houses, which is a lot to absorb in a lightweight system that needs to still work if part of the system fails.