If total brake failure occurs on a steep downhill mountain road and engine braking and handbrake cannot stop the car before a fatal cliff, what is the recognized last-resort emergency measure?

1. Accelerate to attempt jumping across the ravine
2. Look for an emergency escape ramp (避险车道); if unavailable, gently scrape the vehicle body flank against natural roadside obstacles such as hillsides, guardrails, or earth berms to absorb kinetic energy (利用山体、护栏等摩擦减速)
3. Head-on ram into the nearest oncoming heavy truck
4. Throw the passenger door open to create aerodynamic parachute drag