HI!
We are currently thinking about stopping immediately as a last action for automated vehicles with SAE Levels 3, 4 and 5.
The risk of such a maneuver relies on the visibility of the vehicle and its stopping maneuver and the relative speed to other traffic participants in the current scenario.
Has anybody a good source for information, which relative speeds are safe for stopping and for passengers leaving the vehicle?
Thank you very much for your answers!
Some data are available on the SAE website but are good for Formula SAE cars.
If you have data about the time needed to leave the vehicle (it depends from age and ability of the passenger), you can calculate your data adding these to the average time needed for a safe brake that you can calculate, depending on the speed, using a formula from literature (for example "Fundamentals of Vehicle Dynamics" by T. Gillespie).
I would follow the Google path:
Go up to 25 mph. Than the only possible manouvre in an emergency case is stopping (and not cornering anymore).
To my knowledge there is littel literature on this. Only on the limit wehre stopping is better than cornering (as I said ar abou 50 km/h)
Our current approach is quite similar to Google. 50 km/h are seem to be safe as a relative speed. Even 60 km/h should be okay.
Outside of cities and on highways a reliable value is still missing. To calculate an average time to braking is the second half of the problem. The first half includes visibility of the vehicle and reaction times. Thus, a stop would be only valid, if the visibility is given, e.g. by not stopping immediately, but on a place where the vehicle is visible. The functional requirements would be quite high, because the vehicle would have to chose a safe place to stop based on its environment perception.
What do you think?
I have seen in a standard that the deceleration shall not exceed 0.6g. So I think it is more important than the relative speed because of passenger (inside), but if the negative acceleration does not exceed that limit, relative speed might be important because of outside passenger.
I think it is a good idea to add a maximum deceleration of the automated vehicle.
For automated vehicles the view area of the environment perception is one key aspect for their own speed. Thus, the view area limits the driving speed, because of the reaction time to newly perceived obstacles and the maximum reachable deceleration.
A maximum deceleration of 0.6g in several driver assistance systems is chosen not only to protect the passengers inside the vehicle, but also to give vehicles behind it a chance to react and brake and to avoid rear-end collisions caused by a strong brake maneuver of the equipped vehicle.
What I have in mind is the relative speed to others, if the vehicle has already stopped and passengers might need to leave it. If others are approaching with high speeds, the people leaving the vehicle and the vehicle itself could be visible to late and just by standing at a wrong place cause a collision.
I think, if the other driver does not see you, it happens every day . But to avoid a collision to front or rear vehicle, a distance of 2 second (as police always say) must be enough. in every speed, drivers need at least 0.5 second to react, so they have their chance to decide, react and stop the vehicle.
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