In regards to there being more than expected air in the tunnel - the vehicle would be slower, but not much else right? Less air than expected inside the vehicl

In regards to there being more than expected air in the tunnel - the vehicle would be slower, but not much else right? Less air than expected inside the vehicle could be life-threatening for breathers. For humans we could solve this with an emergency oxygen hose at every seat like in planes. Pets and other oxygen dependant lifeforms wouldn't be protected by this system though. An alternative could be to have an electronic hatch at regular distances in the tunnel. So when a vehicle detects a massive oxygen leak inside the cabin, it could signal the nearby tunnel hatch to open. The whole tunnel, and thus also the vehicle [1] would fill with air pretty fast. -- [1] The vehicle would have a large hole in order for oxygen levels to suddenly go from life-sustaining to not. Thus that same hole would serve to refill the vehicle with oxygen coming from the tunnel hatch. However there could be an additional hatch for the vehicle to guarantee airflow. This could maybe even mount directly to a tunnel hatch, so that outside air would come to the vehicle and skip the tunnel.