Wheel chocks are required by law in many places for trucks because they are mechanisms in PLAIN SIGHT that do not fail.
And all my tractors and excavators have hydraulic acculumulators, seem to NEVER break or leak, and within a few seconds lock up all drive mechanisms when the engine is killed. As soon as you turn off a 100,000 pound excavator, you have nothing to do but go home, no levers to pull. Great system.
Very handy on the edge of a cliff when the engine dies and braking power ends. Might not work so well on a pickup at 80 MPH on the freeway.
A hydraulic accumulator on autos, with brains, would be a huge safety factor for braking and parking.
Funny how a backup relief valve disturbs everyone. But all those stupid backflow valves that we lived without for 150 years are gods new standard without question. How many of you got sick from reverse flow water? Better to regulate chickens in the market for bacteria.